A Cyclopædia of Practical Receipts, Processes, and Collateral Information (part 16)

By a foreign invention, patented in 1851 by Mr W. E. Newton, the operations of ‘separations’ and ‘refining’ are conducted by one process. The argentiferous substance, whether in the state of ore or bullion, is reduced to a granulated or spongy state, by fusion along with zinc, or some other metal cheaper than silver, and the zinc is subsequently removed, by digesting the resulting granulated, laminated, or pulverulent alloy, in dilute sulphuric acid, or other acid. The zinc, &c., is recovered by the usual means. This process, carefully conducted, produces metal of great ductility and purity, containing 99% to 99⁄2% of pure gold.

Chemically pure gold is obtained by dissolving the metal in nitro-hydrochloric acid, adding a solution of protosulphate of iron, and collecting and washing the precipitate. In this state it is a brown powder, which acquires a metallic lustre by friction or heat.

Prop. The most marked properties of gold are its rich yellow colour, its ductility, malleability, insolubility in all menstrua except ‘aqua regia’ (nitro-hydrochloric acid), aqueous chlorine, and hydrofluoric acid, and its very slight affinity for oxygen. It melts at a bright red heat (2316° Fahr.—Daniell), and the fused metal has a brilliant green colour. It forms compounds with chlorine, iodine, oxygen, sulphur, &c. Sp. gr. of native gold, 13·3 to 17·7; of pure gold, 19·3 (average); its greatest density is 19·5.

Tests. Metallic gold is characterised by its yellow colour, insolubility in nitric acid, and its ready solubility in aqua regia, forming a rich yellow or amber-coloured liquid, which stains the skin purple. Solutions of gold exhibit the following reactions:—Protosulphate of iron gives a brown precipitate, which acquires a metallic lustre when rubbed;—Protochloride of tin (preferably containing a little perchloride) gives a violet, purple, or blackish precipitate, insoluble in hydrochloric acid;—Sulphuretted hydrogen and hydrosulphide, of ammonia give a black precipitate, insoluble in simple acids;—Ammonia gives a reddish-yellow precipitate (‘fulminating gold’), with tolerably concentrated solutions, either at once or on boiling the liquid;—Liquor of potassa gives a reddish-yellow precipitate with neutral solutions of gold, insoluble in excess.

Estim. 1. In the dry way;—

The quantity of gold in an ALLOY is usually estimated by ‘assaying’ the sample. Before proceeding to the assay, it is necessary to form some estimate of the quantity of other metals (copper or silver, or both) in the specimen to be examined, in order to employ the proper proportion of lead in the ‘cupellation.’ The experienced assayer commonly does this by the ‘assay of the touch,’ and, in certain cases, by a rough preliminary assay. The quantity of lead employed may be about 16 times the weight of the copper present in the sample, and when the alloy contains silver an additional allowance of lead, equal to ⁄10th of its weight, is made on that account. When no silver is present, or it is not required to be estimated, a much larger proportion of lead may be employed. The weight taken for the assay (‘assay pound’) is usually 12 or 6 gr. The alloy and dose of lead being accurately weighed and separately wrapped in small pieces of paper, the assay may be at once proceeded with.

α. Cupellation. This operation, the most important of the whole, has been already described. Unlike silver, gold will bear the highest heat of the furnace without ‘vegetating,’ ‘fuming,’ or being absorbed by the cupel. The loss of weight gives the amount of copper in the alloy.

β. Quartation. The cupelled sample is fused with three times its weight of pure silver (called the ‘witness’), by which the gold is reduced to one fourth of the mass, or less, and in this state may be easily removed.

γ. Parting. The alloy, after quartation, is hammered or rolled out into a thin strip or leaf, curled into a spiral form, and boiled for a quarter of an hour, in a small flask, with about 2⁄2 to 3 oz. of nitric acid (sp. gr. 1·3); and the fluid being poured off, it is again boiled in a similar manner with 1⁄2 to 2 oz. more of nitric acid (sp. gr. 1·2), after which the gold is carefully collected, washed in pure water, and dried. When the operation of ‘parting’ is skilfully conducted, and the acid not too strong, the metal preserves its spiral form; otherwise, it falls into the state of flakes or powder. The second boiling or digestion is technically termed the ‘reprise.’ The loss of weight by ‘parting,’ after deducting that of the ‘witness,’ corresponds to the quantity of silver originally in the specimen.

δ. Annealing. This consists in putting the pure gold obtained by the last process into a small porous crucible or cupel, and heating it to redness in the muffle.

ε. Weighing. This must be done with the utmost accuracy. The weight, in grains troy, doubled or quadrupled, as the case may be, gives the number of carats fine of the alloy examined, without calculation.

According to the ‘old French method’ of assaying gold, the following quantities are taken:—For the assay pound, 12 gr.; fine silver, 30 gr.; lead, 108 gr. These having been cupelled together, the (perfect) button is rolled into a leaf (1⁄2 × 5 inches), twisted on a quill, and submitted to parting with 2⁄2 oz. and 1⁄2 oz. of nitric acid, sp. gr. 1·16 (20° Baumé). The remainder of the process is similar to that above described. Two assays are made in the same manner, with a third on pure gold or gold of a known fineness; and no conclusion is drawn, unless the assay of the latter comes out accurately, and that of the first two correspond to each other.

For alloys containing platinum, which usually consist of copper, silver, platinum, and gold, the method of assaying is as follows:—The alloy is ‘cupelled’ in the usual way, the loss of weight expresses the amount of copper; and the button, made into a riband and treated with sulphuric acid, indicates, by the portion dissolved, that also of the silver present. By submitting the residuum to quartation, the platinum becomes soluble in nitric acid. The loss after digestion in this menstruum expresses the weight of that metal, and the weight of the portion now remaining is that of the pure gold. Gold containing palladium may be assayed in the same manner.

2. In the wet way:

The richness in gold of any substance, whether liquid or solid, when the quantity is small (and indeed in all other cases), is most simply and economically performed by the common method of chemical analysis. The gold may be thrown down from its solution by adding a solution of protosulphate of iron; the precipitate, after being washed, dried, and gently heated, may be weighed as pure gold.

Pois., &c. The soluble preparations of gold (chlorides) are violent poisons. The symptoms resemble those occasioned by corrosive sublimate, but are somewhat less violent. Metallic gold in a minute state of division is also capable of producing very unpleasant consequences, and even endangering life. The antidote is iron filings or a solution of sulphate of iron, given conjointly with an emetic.

Uses. The numerous applications of gold in the arts and the daily transactions of life need only be alluded to here. In medicine, gold has been given in the form of powder, in scrofula and syphilis, by Chrestein, Niel, and others, with apparent advantage.—Dose, ⁄4 gr. to 1 gr., 3 or 4 times a day, in pills, or as a friction on the tongue and gums. An ointment made of 1 gr. of powdered gold and 30 gr. of lard has been applied by Niel to the skin deprived of the epidermis (endermically) in the above diseases.

The more important chemical compounds containing gold, the alloys and commercial forms of the metal, together with certain factitious substances popularly called ‘gold’, are noticed in alphabetical order below:—

Gold, Alloys and Preparations of:—

Gold, Dutch. Mannheim gold, Mosaic g., Or-molu, Pinchbeck, Prince’s metal, Red brass, Similor, Tombac. These names are applied to several varieties of fine gold-coloured brass, differing slightly in tint and in the proportions of copper and zinc. The terms tombac, prince’s metal, similor, and Mannheim gold, are used by some authors to designate alloys consisting of about 85% of copper and 15% of zinc; whereas, according to other authors, prince’s metal and Mannheim gold are synonymous, and are composed of 75% copper and 25% zinc; according to another author, similor consists of about 71⁄2% copper and 28⁄2% zinc, and Mannheim gold of 80% copper and 20% zinc; and, again, according to another author, similor and Mannheim gold are synonymous, and are applied to alloys of copper containing from 10 to 12% zinc and from 6 to 8% tin. Seeing that such inextricable confusion exists in the employment of the terms above mentioned, it is desirable to discard them altogether. At the celebrated works of Hegermühl, near Potsdam, the proportions copper, 11 parts, to zinc, 2 parts, are employed to produce a metal which is afterwards rolled into sheets for the purpose of making Dutch leaf-gold. This alloy has a very rich, deep gold colour. Its malleability is so remarkable that it may be beaten out into leaves not exceeding ⁄52900 inch in thickness.

Gold, Facti′′tious. Prep. From copper, 16 parts; platinum, 7 parts; zinc, 1 part; fused together. This alloy resembles in colour gold of 16 carats fine, or ⁄3, and will resist the action of nitric acid, unless very concentrated and boiling.

Gold, Grain. Syn. Aurum granulatum, L. Prep. From cupelled gold, 1 part; silver, 3 parts; melted together, and poured in a small stream into water; the silver being afterwards dissolved out by digestion in boiling nitric acid, and the grains, after being well washed in water, heated to redness in a crucible or cupel. Used to make preparations of gold.

Gold, Jew′eller’s. This term is applied to alloys of gold used for trinkets and inferior articles of jewelry, ranging from 3 or 4 carats fine upwards; or which are too inferior to receive the ‘Hall mark’. The lowest alloy of this class is formed of copper, 16 parts; silver, 1 to 1⁄2 part; gold, 2 to 3 parts; melted together. This is worth only from 8s. 6d. to 9s. 6d. the oz.

It has recently been found that gold of the quality of 12 carats, or less, if alloyed with zinc instead of the proper quantity of silver, presents a colour very nearly equal to that of a metal at least 2⁄2 to 3 carats higher, or of 8s. or 10s. an ounce more value; and the consequence has been that a large quantity of jewellery has been made of gold alloyed in this manner; and the same has been purchased by some shopkeepers, very much to their own loss as well as that of the public; inasmuch as a galvanic action is produced, after a time, upon gold so alloyed, by means of which the metal is split into several pieces, and the articles rendered perfectly useless.

Gold, Leaf. Syn. Gold-leaf. Gold reduced to leaves by hammering it between thin animal membrane. Its preparation constitutes the trade of the goldbeater. These leaves are only ⁄28200 of an inch in thickness. Gilt silver is hammered in the same way, but the leaves are thicker. The latter is called party gold. Both are used by artists and gilders, and by druggists to gild pills, &c.

Gold, Powdered. Syn. Divided gold, Gilding powder, Gold bronze, Gold colour; Auri pulvis. Prep. Gold, 1 part; mercury, 7 parts; form an amalgam, and expose it to heat until all the mercury is volatilised; or the mercury may be dissolved out with hot nitric acid. In either case the residuum is to be powdered, washed, and dried. If the quantity operated on is considerable, the process should be so conducted as to save the mercury.

From gold leaf and honey ground together, as the last, by means of a stone and muller. This is the plan commonly adopted in the small way by artists.

From a solution of gold in aqua regia precipitated by protosulphate of iron, the resulting powder being washed, dried, and gently heated, This gives pure gold.

Uses, &c. Powdered gold is employed in gilding by japanners and by artists. It is either sold in powder (gold in powder), or made up into shells (gold in shells). Its use in medicine has been already noticed.

Gold, Standard. The standard gold of this country is an alloy of pure gold, 11 parts, with pure copper, 1 part. Formerly the alloy consisted partly of silver, as found in some of the older coins now in circulation. It is often spoken of as 22 carats fine.

Gold, Chlorides of:

1. Monochloride. AuCl. Syn. Aurous chloride, Protochloride of gold. A yellowish-white mass, formed when a solution of trichloride of gold is evaporated to dryness, and the residuum is exposed to a heat of about 440° Fahr., until fumes of chlorine cease to be evolved. It is insoluble in water, which decomposes it, slowly when cold, but rapidly by the aid of heat, into metallic gold and the trichloride.

2. Trichloride. AuCl3. Syn. Auric chloride, Terchloride of gold, Trichloride of gold, Auri chloridum. Prep. Gold, 1 part, dissolved by aid of heat in nitro-hydrochloric acid, 8 parts, and evaporated down to near dryness, and allowed to crystallise.

Prop. Orange-red crystalline needles, or ruby-red prismatic crystals; deliquescent; soluble in water, ether, and alcohol, forming a deep-yellow solution; at the heat of 500° Fahr. it suffers decomposition, chlorine being given off and pure gold left behind. It is reduced by ferrous sulphate, oxalic, sulphurous, formic and phosphorous acids, as well as by most of the metals, to metallic gold. It combines with several of the metallic chlorides, forming a series of double salts, which are mostly yellow when in crystals, and red when deprived of water.

Uses, &c. It has been employed by Duportal, Chrestien, Niel, Cullerier, Legrand, and others, as a substitute for mercury, in scrofula, bronchocele, chronic skin diseases, &c.; also as a caustic.—Dose, ⁄20 gr., dissolved in distilled water, or made into a pill with starch; or, in frictions on the gums, in quantities of ⁄16 to ⁄10 gr. Its most important use, however, is as a reagent in photography, large quantities being manufactured for use as a chief agent in toning photographic prints.

To some extent it is also used for electro-gilding, and mixed with excess of bicarbonate of potassium, it forms a good yielding solution for small articles of copper. These are to be first cleaned with dilute nitric acid, and then boiled for some time in the mixture.

The above is the salt generally referred to under the name of the ‘chloride of gold,’ or in commerce occasionally as the ‘muriate of gold.’

Gold, Chloride of, and Sodium. AuCl3. NaCl. 2Aq. Syn. Aurochloride of sodium; Sodii aurochloridum. Prep. Auric chloride, 85 parts; chloride of sodium, 16 parts; dissolve in a little distilled water, evaporate until a pellicle forms, then put it aside to crystallise. It forms beautiful orange-coloured rhombic prisms.

Dose, &c. ⁄20 to ⁄12 gr., made into a pill with starch or lycopodium, in the same cases in which the terchloride is ordered. Mixed with 2 or 3 times its weight of orris powder, it has been used in frictions on the tongue and gums, and an ointment made with 1 gr. of the salt, mixed with 36 gr. of lard, has been applied to the skin deprived of the epidermis by a blister.

Gold, Cyanide of. AuCy3. Syn. Auric cyanide. Prep. Add a solution of pure cyanide of potassium to a solution of pure auric chloride as long as a precipitate forms, carefully avoiding any excess; wash, and dry the precipitate.

Prop., Uses, &c. The salt is a pale-yellow powder, insoluble in water, but very soluble in a solution of cyanide of potassium, forming the double cyanide of gold and potassium so largely used in the electrotype process. Cyanide of gold is employed to a certain extent in medicine.—Dose, ⁄12 to ⁄10 gr., made into a pill, in the usual cases in which gold is administered. The first formula is essentially similar to that of the French Codex.

Gold, Extraction of, by Sodium Amalgam. (Crookes’ Method, Patented.) In the extraction of gold by amalgamation serious difficulties are often occurring through the ‘flouring’ or ‘sickening’ of the mercury employed, and the prevention of the amalgamation by a coating of tarnish on the gold. So much is this the case that losses of from 30 to 60 per cent. of the gold are usually incurred, and, in many cases a still more serious loss of mercury.

When certain minerals, as tellurium compounds, pyrites, &c., occur in the gold ore, the mercury is apt, on trituration, to become subdivided into excessively minute globules, which, owing to their tarnished condition, refuse to unite, and are consequently washed away, it being almost impossible to separate them from the heavier portions of the ore. This is technically called ‘flouring,’ ‘granulating,’ &c. Besides this, certain of these minerals affect the mercury in another way, that is, by ‘sickening’ it, or causing it to lose its bright surface and fluidity, and prevents its amalgamating with the gold. Besides the inconvenience and loss thus caused, a further loss of gold takes place from the inability of the ordinary mercury to touch or amalgamate tarnished gold, unless it is ground with it, for a more lengthy period than is found practicable in most cases.

Mr Crookes, F.R.S., has, by means of the addition of a certain proportion of sodium, in the form of an amalgam, to the mercury, effectually prevented this serious loss of gold and mercury. By adding certain quantities of amalgams B and C, an amount which, differing from each ore, is ascertained by experiment, the ‘flouring’ and ‘sickening’ of the mercury is effectually prevented, the mercury remaining throughout in the best condition. The addition of about one tenth per-centage of amalgam A, at intervals of some hours, increases most powerfully the affinity of the mercury for the precious metals, and secures a more thorough amalgamation.

This invention has met with general approval, and experiments conducted at many mines show its great practical value, giving an increase of from 5 to 30 per cent. in the yield of gold, and, in fact, with many pyrites that yielded no gold to the ordinary amalgamation process, gave a considerable yield of gold to the sodium amalgamation process. This has led to its use in most mines, both silver and gold, in America.

Gold, Iodide of. AuL3. Syn. Auric iodide, Tri-iodide of gold, Gold teriodide, Auri iodum. Prep. Add a solution of trichloride of gold to one of iodide of potassium. The resulting precipitate is at first redissolved on agitation, a soluble double iodide being formed; subsequently the iodide of gold is precipitated, leaving the supernatant liquor free of colour.

Prop., Uses, &c. A dark-green powder, easily soluble in hydriodic acid. It is occasionally employed as a medicine, and, like other preparations of gold, is of an alterative character.—Dose. About ⁄16th of a grain.

Gold, Oxides of:—

1. Monoxide. Au2O. Syn. Aurous oxide, Protoxide of gold. Prep. Formed by treating the aurous chloride with strong potassium hydrate. Green powder, somewhat soluble in potassium hydrate solution, and readily decomposing into metallic gold and auric oxide.

2. Trioxide. Au2O3. Syn. Auric oxide, Oxide of gold, Peroxide of gold, Auric acid, Auri oxidum. Prep. Magnesic oxide, 4 parts; auric chloride, 1 part; water, 40 parts; mix, boil, and wash the precipitate with water, dilute nitric acid, and again with water. It must be dried in the shade.

Reddish-yellow powder, easily decomposed by heat; readily soluble in hydrochloric and hydrobromic acids and strong nitric acid, but insoluble in water and the other acids. Forms unstable salts with the alkalies.

Uses, &c. Trioxide of gold has been given in scrofula, &c., in doses of ⁄12 to ⁄2 gr., or 1 gr., in scrofula, syphilis, &c., made into a pill with extract of mezereon.

Gold, Ammoni′uret of*. Syn. Aurate of ammonia, Berthollet’s fulminating gold; Aurum ammoniatum, Ammoniæ auras, L. Prep. By adding ammonia to a solution of gold in aqua regia (trichloride), as long as a reddish-yellow precipitate (fulminating gold) forms; the latter must be collected, washed, and dried with the greatest possible caution.

Obs. Ammonia fails to precipitate trioxide of gold from solutions which are not tolerably concentrated, and in those containing free acid or ammoniacal salts the precipitate only forms upon boiling the solution. Before adding the ammonia, it is, therefore, proper to drive off the excess of acid, if any, by the application of heat. See Fulminating Compounds.

Gold, Sul′phide of. Au2S3. Syn. Sulphuret of gold, Tersulphuret of g.; Auri sulphuretum, L. Prep. Transmit a current of sulphuretted hydrogen gas through a solution of terchloride of gold in water; or add hydrosulphuret of ammonia to the same solution; collect the precipitate, wash it with cold distilled water, and dry it in the shade.

GOLD DETER′GENT. Prep. (Upton.) Take quicklime, 1 oz.; sprinkle it with a little hot water to slake it, then gradually add boiling water, 1 pint, so as to form a milk. Next dissolve pearlash, 2 oz., in boiling water, 1⁄2 pint; mix the two solutions, cover up the vessel, agitate occasionally for an hour, allow it to settle, decant the clear, put it into flat half-pint bottles, and well cork them down.

Use. To clean gilding, &c., either alone or diluted with water. It is applied with a soft sponge, and then washed off with clean water. It is essentially a weak solution of potassa, and may be extemporaneously prepared by diluting solution of potassa (Ph. L.) with about 5 times its volume.

GOLD SHELLS. Gold leaf or powdered gold ground up with gum-water, and spread upon the insides of shells. Used by artists.

GOLD SIZE. Syn. Gilding size, Gilder’s s., Gold colour. Prep. 1. (Oil size.) Drying or boiled oil thickened with yellow ochre or calcined red ochre, and carefully reduced to the utmost smoothness by grinding. It is thinned with oil of turpentine. Improves by age. Used for oil gilding.

2. (Water size.) Parchment or isinglass size, mixed with finely ground yellow ochre. Used in burnished or distemper gilding.

GOLD-BEAT′ER’S SKIN is prepared from the peritoneal membrane of the cæcum of the ox. It is used to separate the leaves of gold whilst under the hammer, as a nearly invisible defensive dressing for cuts, as a fabric for court plaster, &c.

GOLDEN SEAL. See Hydrastis canadensis.

GONG METAL. See Bell Metal.

GONIOM′ETRY. The art of measuring the angles of crystals, by means of a GONIOMETER; a most important matter in chemistry and mineralogy. The only accurate and simple instrument of this kind is the REFLECTING GONIOMETER invented by Dr Wollaston. Facility in using this instrument is readily acquired by a few trials.

GOOSE. This bird, the Anser domesticus, is a favourite article of food almost everywhere, and may fairly claim a similar position amongst poultry to that occupied by “good Sir Loin” among joints of meat. The vulgar inuendos occasionally heard to its prejudice should be directed against the cook rather than the bird, as it is only when it is unskilfully dressed and too highly seasoned that it is apt to disagree with that “irascible member of the interior,” a delicate or overloaded stomach. Undue susceptibility in that quarter may, however, be generally allayed by an oblation, in the shape of a little ‘eau de vie,’ used as sauce or gravy. Formerly, almost miraculous virtues were attributed to this bird. Its flesh was said to promote longevity, to cure hydrophobia, and to be aphrodisiac. The fat (GOOSE GREASE; ADEPS ANSERIS), mixed with honey, was supposed to be “good against the bitings of a mad dog.” At the present day it is occasionally used in clysters, and, when scented, as a pomade to make the hair grow, for which purpose it is said to be superior to bear’s grease. In quantity it is an emetic of very easy action. The large feathers of the wings (quills) are used for writing. The small feathers form the common stuffing of our beds.

GOOSE′BERRY. The fruit or berry of Ribes grossularis. Unripe fruit, cold and acidulous; ripe fruit, wholesome and slightly laxative; but the seeds and skins should not be eaten, as they are very indigestible; the juice of the green fruit is made into wine (English champagne); the seeds, washed and roasted, were formerly used as a substitute for coffee (GOOSEBERRY COFFEE). Gooseberries are preserved by simply bottling them, and keeping them in a very cold place. See Cheese, Fool, Fruit, &c.

GOULARD. Syn. Goulard’s extract. See Solution of Diacetate of Lead.

GOUT. Syn. Arthritis, L. A painful disease that chiefly attacks the male sex, particularly those of a corpulent habit and robust frame. Persons who live temperately and take much exercise are seldom troubled with gout. Indolence, inactivity, luxurious habits of life, and free living, are the chief exciting causes of this disease; but excessive study, grief, watchfulness, exposure to cold, and the too free use of acidulous liquors, also occasionally bring it on. In some persons it is an hereditary disease.

Symp. Gout is generally preceded by unusual chilliness of the feet and legs, and a numbness or a sensation of prickling along the lower extremities; the appetite fails, flatulency, indigestion, torpor, and languor ensue, and extreme lassitude and fatigue follow the least bodily exercise; the bowels become costive, and the urine pallid. The fits usually come on in the night; the patient is awakened by the severity of the pain, generally in the first joint of the great toe, or occasionally in the heel, whole foot, or calf of the leg. The pain resembles that of a dislocated joint, accompanied by a sensation resembling the effusion of cold water; the pain increases, rigors and febrile symptoms ensue, accompanied with local throbbing and inflammation. Sometimes both feet and legs are attacked; at others, only one. Towards morning the patient generally falls asleep, and sinks into a state of copious perspiration, from which he awakes comparatively recovered. This constitutes what is called a ‘fit of gout.’ These fits or paroxysms are apt to return at intervals, commonly every evening, with more or less violence; and when frequent, the disease usually extends its action, the joints become affected, and concretions of a chalky nature (chalk stones, gout stones) are formed upon them, and they become stiff and nearly immovable.

Treat. A plain or vegetable diet, moderate exercise, and the use of warm laxatives, gentle tonics, diaphoretics, and diuretics, are among the best preventives. The moderate use of alkaline remedies, as potassa and magnesia, has also been recommended. To relieve the fit of gout, or to check it at its commencement, the affusion of cold water will be often found effective. The use of the ‘eau médicinale’, or the ‘vinum colchici’ of the Pharmacopœia, may also be had recourse to; a due dose of which taken at bedtime will frequently carry off the paroxysm, and nearly always mitigate the symptoms. The effect of the above remedies do not greatly differ from each other. The action of both medicines is accompanied with great languor, and a deadly nausea or sickness, which terminates in vomiting or a discharge from the bowels, or both. These symptoms have often reached an alarming extent, and in some constitutions follow even a moderate dose. This method of cure should not, therefore, be unadvisedly and incautiously adopted.

Another remedy which has been recommended for gout is lemon juice, but experience has proved that this agent is not to be depended on. The dose proposed by Dr O. Rees, who originated this treatment, was 2 or 3 fl. oz., twice or thrice a day.

To ensure the efficacy of lemon juice, it must be expressed from the fruit into the glass shortly before being taken. That purchased at the shops is generally stale and disagreeable, and is often worse than useless. In some cases it is advisable to take the juice undiluted, but the more common practice is to mix it with about an equal quantity of water. See Rheumatism, Colchicum, Draught (Anti-arthritic), Lemon Juice, Vinegar of Colchicum, Wine of Colchicum, &c.

Gout Cor′dial. Prep. Rhubarb, senna, coriander seed, sweet-fennel seed, and cochineal, of each 2 oz.; liquorice root and saffron, of each 1 oz.; raisins, 2⁄2 lbs.; rectified spirit of wine, 2 gals.; digest for 14 days, press, and filter. Used in gout and rheumatism. Aromatic and slightly laxative.—Dose, 1 to 3 table-spoonfuls.

Gout Med′icine. (Duncan’s.) A mixture of wine of colchicum, wine of opium, and tincture of saffron.

Gout Rem′edy. (Alexander’s.) According to Dr Paris, this contains—aniseed, cumin seed, ginger, hermodactyles, pepper, and scammony.

Gout Specific. (Murray’s.) A mixture of iodide of potassium, sulphate of magnesia, and wine of colchicum, disguised with an aromatic tincture.

GOUTTES AMERES. [Fr.] See Drops (Bitter).

GRAD′UATOR. See Vinegar.

GRAFTING COM′POST. Clay tempered with water, to which a little linseed oil is sometimes added. Used to cover the joint formed by the scion and stock in grafting.

GRAINS OF HEALTH, Dr Franck’s—Gesundheitspillen—Grains de Santé, ou Grains de Vie, du Docteur Franck. Silvered pills, containing 1 part gamboge and 4 parts aloes. (Hager.)

GRAINS OF PAR′ADISE. Syn. Guinea grains, Meleguetta pepper. The seeds of the Ammomum meleguetta. Grains of paradise are hot, acrid, and aromatic, and in general properties similar to the other peppers. In some parts of the world they are used as a condiment. They are principally employed in these countries to impart a false strength to wine, beer, spirits, and vinegar.

GRANIL′LA. A small inferior variety of cochineal (which see).

GRANULA′TION. The act or process of forming, or breaking into, grains or small masses.

The granulation of MEDICINES has of late years received considerable attention from both foreign and British pharmaceutists. In France, granulated powders (POUDRES GRANULÉES) are coming into general use in place of impalpable powders, the most unpleasant of all forms of medicine. The French process consists in enveloping the particles of medicines in syrup by means of heat and constant stirring. Mr Banner, of Liverpool, has lately introduced a method of granulating medicines far preferable to that of the French pharmaceutists. The powder to be granulated is placed in a mortar, and mucilage of gum acacia is gradually added until a crumbly mass is made; this is then rubbed through a wire sieve (about 12 meshes to the inch), and the granules produced are spread out on paper, and left to dry spontaneously, or they are placed in a copper pan, and kept in constant motion over a stove until dry; when perfectly dry, they are placed in a mortar, and sufficient quantity of strong tincture of tolu (3 dr. to 1 oz.) is added to them, until by constant stirring they all appear glossy and shining; they are then dried again by a gentle heat, being kept in constant motion. The granules thus formed keep well, are tasteless, and are much more elegant and agreeable preparations than pills or ordinary powders. Many saline substances are granulated by the simple process of dissolving the salt in water, and evaporating to dryness with constant stirring.

Metals are granulated (reduced to drops, grains, or coarse powder) by pouring them, in the melted state, into water. In many cases they are allowed to run through the holes of a species of colander or sieve to produce minute division; and in order to render the drops spherical, they are allowed to fall from a sufficient height to permit of their acquiring the solid state before striking the water. Lead shot is made in this way. Shot towers are often upwards of 100 feet in height. See Copper, Gunpowder, Powder, Zinc, &c.

GRAPES. Syn. Uvæ, L. The fruit of Vitis vinifera, or the common grape vine. Ripe grapes are cooling and antiseptic, and in large quantities diuretic and laxative. They are very useful in bilious affections and dyspepsia, and in all febrile, putrid, and inflammatory complaints. The skin and seed, which are indigestible, should be rejected. “Grapes which contain a large quantity of sugar are, if taken without the husks, the safest and most nutritive of summer fruits.” (Cullen.) “The subjects of pulmonary affections, who pass the summer in Switzerland, may try the effects of a course of grapes, ‘cure de raisins,’ a remedy held in high estimation in several parts of the Continent.” (Sir J. Clark.)

Grapes, in bunches are preserved by wrapping them in silver paper, and packing them in dry bran. Each bunch is suspended by the stem with the fingers of one hand, whilst the bran is poured round it with the other; the jar being occasionally gently shaken as the process of packing proceeds. Some paper is then laid over the top of the jar, the mouth or cover of which is, lastly, tied firmly over with bladder, to exclude the air and moisture. See Fruit, &c.

GRAPH′ITE. See Plumbago.

GRATE. A frame of iron bars used for burning coal as fuel. In the construction of a grate it is desirable to make the perpendicular height of the fuel as great as is consistent with safety. A stratum of burning coal will radiate considerably more heat into an apartment if placed vertically than if arranged horizontally; besides which a great saving of fuel will be effected in proportion to the heat radiated. Hence the faulty construction of the old-fashioned wide grates. The fuel should also be so divided in a fireplace as to be easy of ignition, and so placed as to give free access of air to all its parts, as the smoke is then more likely to be burnt.

GRAV′EL. A collection of small pebbles commonly mixed with sand or clay, or both. Gravel for garden walks is chosen for its fine colour and binding properties. The gravel of Kensington and Wimbledon is esteemed the finest in the world. Gravel walks when once in order, may be rendered nearly equal to asphalt by pouring over them tar or a mixture of tar and pitch, absorption being promoted, if required, by the application of a hot iron.

Gravel. In pathology, a term popularly applied to calculous matter formed in the kidneys, and passing off in the urine; and sometimes to distinct calculi or concretions in the bladder itself.

An attack of gravel, as commonly understood, is accompanied by a deposit of red, gritty, sand-like particles in the urine, which do not dissolve when the urine is heated. The deposit consists of uric acid. Pains in the loins are a common accompaniment of gravel, and there is also sometimes pain in passing water.

Treat. Give twenty minims of solution of potash (of the B. P.) three times a day in barley water; or twenty grains of bicarbonate of soda, also three times a day. If the attack be attended with much pain a brisk dose of Gregory’s powder should be additionally taken every morning. Vichy Water will also be found a useful remedy. See Calculus.

GRAVIM′ETER. See Hydrometer.

GRAV′ITY. Syn. Gravitation. The attractive force by which bodies fall towards the centre of the earth. Weight is the measure of gravity. The determination of the relative weight of bodies with reference to a given standard, is explained under Specific Gravity.

GRA′VY. The juice or liquid matter that drains from dressed meat after it is placed on the dish for serving. The common practice among cooks is to pour a spoonful or two of boiling water or broth over the joint, to increase the quantity. The natural gravy that oozes from the meat after it is cut is the richest and most wholesome. Made gravies are prepared by adding spice and flavouring to the foregoing, or to strong meat soup.

The gravy for roast meat is usually made by sprinkling a little salt on the joint after it is placed in the dish, and then pouring some boiling water over it; this washes off some of the brown, and makes a coloured liquid in the dish.

Another method for making gravy for roast meat is the following:—Take any bones, scraps of cold meat, or trimmings of the joint, put them in a half pint of water, with a little salt and half an onion, let them stew all the time the meat is roasting; colour with a little burnt sugar. When the meat is done, pour the dripping from it carefully into a basin, leaving the gravy at the bottom of the tin; strain the gravy you have made into this, let it boil, and pour round (not over) the meat. If the gravy is liked thick, put a dessert-spoonful of flour, mixed into a smooth paste, with two of cold water, into the saucepan five minutes before you strain it. See Sauce.

GRAY. Syn. Grey; Gris, Fr. A mixture of black and white. Delicate grays result from mixture of the three elementary colours, red, yellow, and blue, in which the blue preponderates to a greater or less extent.

GRAY DYE. Syn. Teinte grise. Gray is dyed with the same materials as black, but both the bath and mordaunt are used in a more diluted state. Cotton goods may be worked in sumach and then in copperas; this gives rather a bluish grey, which may be modified to any particular hue by the addition of suitable colouring matter. To make it yellowish, a small amount of fustic and alum are employed; to make it ‘fuller,’ peachwood and Lima-wood with alum are used. The methods of obtaining grey on SILK and WOOL are very numerous; they are similar in principle to the above, all depending on the blending of the three primary colours, or on the modification of weak blacks. See Black Dye.

GREASE. A general term applied to soft animal fats; as BEAR’S GREASE, GOOSE GREASE, &c.

Grease. An inflammatory affection of the heels of horses, which produces dryness, scurfiness and stiffness. The treatment consists of emollient poultices, accompanied with physic and diuretic balls, to subdue the inflammation, followed by mild astringent lotions or ointments.

GREAVES. Syn. Graves. The sediment of melted tallow, consisting chiefly of animal membranes mixed with fat, made up into cakes. Used as a coarse food for dogs.

GRE′CIAN WATER. See Hair Dyes.

GREEN. Syn. Viridis, L.; Vert, Fr. Of the colour of the leaves of growing plants; subst. a green colour.

GREEN DYE. Syn. Teinte verte, Fr. All the green dyes in use, with the practically unimportant exception of Chinese green and oxide of chromium green, are compounded of blue and yellow. The goods, in practice, are generally dyed blue first, observing to regulate the shade according to that of the intended green; they are then dried, rinsed, and passed through a yellow bath, with the like precautions, until the proper shade is obtained. See Blue Dye, Yellow Dye, &c.

GREEN PIG′MENTS. Several of the green pigments of commerce are obtained from copper. Oxide of chromium furnishes some which are very beautiful. Many are formed by the mere mechanical admixture of blue and yellow pigments. The bright blues and yellows, when mixed in this way, produce the liveliest greens; orange, or red and blue, and the yellowish browns and blue, the more dingy greens. In this way are produced all the extemporaneous greens of the artist. Nickel and titanium also furnish green colours, but these are not in common use. The following list embraces all the best-known and most useful green pigments:—

Green Arsen′ical. Arsenite and aceto-arsenite of copper. See Green, Scheele’s and Schweinfurt (below).

Green, Barth’s. From yellow lake, Prussian blue, and clay, ground together.

Green, Bice. Same as mountain green.

Green, Bremen. This is properly green verditer, but other preparations are frequently sold under the name.

Green, Brighton. A mixture of impure acetate of copper and chalk, prepared as follows:—

To sulphate of copper, 7 lbs., add sugar of lead, 3 lbs.; each separately dissolved in water, 5 pints; mix the solutions, stir in of whiting, 24 lbs., set the resulting paste on chalk stones, and when dry grind it to powder.

Green, Brunswick. This is probably a crude chloride of copper, but a mixture of carbonate of copper and alumina or chalk is now commonly sold under the name in the shops.

Prep. 1. A saturated solution of sal ammoniac, 3 parts, is poured over copper filings or shreds, 2 parts, contained in a vessel capable of being closed up, and the mixture is kept in a warm place for some weeks, when the newly formed green pigment is separated from the unoxidised copper, by washing the mixture on a sieve; it is then edulcorated with water, and slowly dried in the shade. Colour very deep and rich. The lighter shades are produced by the addition of sulphate of baryta.

2. A solution of crude carbonate of ammonia or bone spirit is added to a mixed solution of alum and blue vitriol, as long as it affects the liquor; in a short time the precipitate is collected, washed and dried. The various shades of green are produced by using different quantities of alum, which pales and cheapens it.

Green, Chrome. The superb green pigment used by enamellers under this name is the green oxide or sesquioxide of chromium. A hydrated oxide of chromium forms the emerald green of Pannetier; it is prepared by melting in a crucible equivalent quantities of anhydrous boracic acid and bichromate of potassium, and treating the fused mass with water. The hydrated oxide thus produced is washed and finely triturated.

The chrome green of the oil and colour shops is a mixture of chrome yellow and Prussian green.

Green, Cop′per. Green bice or mountain green, Brunswick green, emerald green, verditer, and several other well-known pigments, may be thus named.

Green, Em′erald. This term is commonly applied to the aceto-arsenite of copper, as prepared in England. It is the same compound, chemically speaking, as Schweinfurt green (which see).

Prep. A pulp is formed with verdigris, 1 part, and boiling water q. s., and after being passed through a sieve, to remove lumps, is added gradually to a boiling solution of arsenious acid, 1 part, in water, 10 parts, the mixture being constantly stirred until the precipitate becomes a heavy, granular powder, when it is collected on a calico filter, and dried on chalk stones.

Green, Frise. Syn. Friezland green. This resembles Brunswick green.

Green, Gellart’s. A mixture of cobalt blue and flowers of zinc with some yellow pigment.

Green, Impe′rial. Schweinfurt green (see below).

Green, Iris. A pigment prepared by grinding the juice of the petals of the blue flag with quicklime. It is very fugitive.

Green Lake. See Lake.

Green, Min′eral. This is the same as mountain green.

Green, Mitis. Another of the many synonyms of Schweinfurt green.

Green, Mountain. This pigment is properly the native green carbonate or bicarbonate of copper (malachite) ground to powder, either with or without the addition of a little orpiment or chrome yellow. That of the shops is commonly prepared by adding a solution of carbonate of soda, or of potassa, to a hot mixed solution of sulphate of copper and alum. Green verditer is commonly sold for this article. According to Watts, mountain green is the same as Neuwieder green.

Green, Neuwieder. Schweinfurt green mixed with gypsum or sulphate of baryta.

Green, Prussian. The sediment of the process of making Prussian blue from bullock’s blood or horns, before it has had the hydrochloric acid added to it. It is also prepared by pouring liquid chloride upon freshly precipitated Prussian blue. As now sold, this pigment is generally a mixture of Prussian blue and gamboge.

Green, Rinman’s. This resembles that of Gellert.

Green, Sap. A very fugitive pigment, prepared from the juice of buckthorn berries. The berries are allowed to ferment for a week or eight days in a wooden tub. The juice is then pressed out, strained, a little alum added, and the whole evaporated to a proper consistence; it is next run into pigs’ bladders, and hung up in a dry situation to harden. An inferior article is made from the juice of black alder, and of evergreen privet. It is a common practice to add ⁄4 pint of lime water and ⁄2 oz. of gum Arabic to every pint of either of the above juices.

Green, Scheele’s. This is arsenite of copper.

Prep. 1. White arsenic (in powder), 1 part; commercial potash, 2 parts; boiling water, 35 parts; dissolve, filter, and add the solution gradually, whilst still warm, to a filtered solution of sulphate of copper (cryst.), 2 parts, as long as a precipitate falls; lastly, wash the newly formed pigment with warm water, and dry it.

2. (Ure.) Powdered arsenious acid, 11 oz.; carbonate of potassa, 1⁄2 lb.; boiling water, 1 gall.; dissolve, filter, and add the solution, as before, to another solution of crystallised sulphate of copper, 2 lbs., in water, 3 galls. Prod. 1⁄2 lb. A very fine grass-green colour.

Green, Schweinfurt. This splendid green pigment is the aceto-arsenite of copper.

Prep. 1. Acetate of copper and arsenious acid, equal parts, are each dissolved separately in the least possible quantity of boiling water, and the solutions mixed whilst still as hot as possible; an olive-green precipitate falls, which, by being boiled in the liquor 5 or 6 minutes, changes to a dense granular powder of a superb green colour.

2. Instead of boiling the solution containing the precipitate, it is allowed to cool and stand for several hours, or until the powder assumes a granular and beautiful tint. Very rich.

3. (Kastner.) Arsenious acid, 8 lbs., is dissolved in water as before, and added to verdigris, 9 or 10 lbs., diffused through water q. s., at 120° Fahr., the pap of the other being first passed through a sieve; the mixed ingredients are then set aside till the mutual reaction produces the proper shade.

4. (Dr Ure.) Sulphate of copper, 50 lbs., and lime, 10 lbs., are dissolved in good vinegar, 20 galls., and a boiling hot solution of white arsenic, 50 lbs., is conveyed as quickly as possible into the liquor; the mixture is stirred several times, and then allowed to subside, after which it is collected on a filter, dried and powdered. The supernatant liquor is employed the next time for dissolving the arsenic.

5. See Green, Emerald (above).

Obs. This is a very fine, permanent green pigment. “A great deal of needless alarm has been excited about its supposed deleterious effects. It is extensively employed for staining wall-papers, and persons inhabiting rooms thus papered are said to have had their health seriously deranged by the arsenical fumes evolved from it. Now, it is utterly impossible that arsenic could volatilise from such a compound at ordinary temperatures; it does not decompose at any temperature below redness.” (Watts.) [It is, however, probable that the air of such apartments is sometimes charged with the poisonous pigment through its becoming mechanically detached from the paper. To breathe an atmosphere so impregnated would be dangerous. The use of papers coloured with Scheele’s green, especially of the kind called ‘flock,’ should, therefore, be carefully avoided.—Ed.]

Verd′igris. See Copper (Acetates) and Verdigris.

Green, Verd′iter. This is essentially a mixture of oxide and carbonate of copper in uncertain proportions, with chalk. Factitious green bice and mountain green have a like composition. See Verditer.

Green, Verona. The mineral called green earth.

Green, Vienna. The same as Schweinfurt green.

GREEN SICKNESS. See Chlorosis.

GREEK FIRE. This compound, so much used in ancient warfare, is believed to have had naphtha for its chief ingredient. According to some authorities, it was a mixture of asphalt, nitre, and sulphur.

GREGORY’S SALT. The crude hydrochlorate of morphia, prepared by Gregory’s process. It is a double hydrochlorate of morphia and codeia.

GRINDELIA ROBUSTA. A perennial plant belonging to the natural order Compositæ; a native of California, in which state it is largely used against poisoning by the “poison oak” (the Rhus toxicodendron). Of late years it is said to have been in American medical practice used with excellent effect in asthma and kindred diseases. Dr Q. C. Smith, writing to the ‘Pacific Medical and Surgical Journal’ for April, 1875, states one patient to whom pills made of the solid extract were administered, had suffered from severe and frequent attacks of asthma since childhood, and had found no relief from various remedies. Dr Smith gave his patient the extract of the grindelia in pills of three grains each, one three times a day for two or three days, then a pill at bedtime only, for eight or ten days longer. Under this mode of treatment the attacks are said to have been much less severe, and less frequent; the patient not only gaining in strength and general health in the meantime, but having experienced an immunity from attack for four months. The parts of the plant used are the selected leaves and tops.

GRIND′ING. The operation of reducing substances to powder by attrition or friction. In the laboratory, the term is chiefly applied to powdering by means of a mill or by mechanical power, in opposition to simple pounding or trituration in a mortar or with a slab and muller. All the principal powders, paints, &c., sold by the druggist, drysalter, and colourman, are reduced in the drug or colour mill. Recently machinery has even been applied to the common mortar. An ingenious and very useful contrivance of this kind is the ‘mechanical mortar’ of Mr H. Goodhall, of Derby.

GRIND′STONES. (Artificial). Washed siliceous sand, 3 or 4 parts; shell-lac, 1 part; melt together, and form the mass into the proper shape whilst warm, with strong pressure. The fineness of the sand must depend on the work the stone is intended for. The same composition is formed upon pieces of wood, as corn rubbers, and for the purpose of sharpening knives, and cutting stones, shells, &c. See Emery.

GROATS. Syn. Grits; Grutellum, Avena decorticata, Avenæ semina, Avena (Ph. L.), L. Common oats, deprived of their exterior integuments or husks. This is generally effected in a mill, which, at the same time, cuts them into two or three pieces. When crushed flat, they are denominated Embden groats.

GROUT. Mortar reduced to a thin paste with water, used to fill up the joints of masonry and brickwork. A finer kind is used to ‘finish off’ the best ceilings.

GRUEL. Syn. Oatmeal gruel, Water g.; Decoctum avenæ, L. Oatmeal or groats boiled with water to a proper consistence, and strained. It is variously flavoured to suit the palate; but the addition of a little white sugar, and finely powdered Jamaica ginger, with or without a glass of wine, is the least likely to offend the stomach. Nutmegs, cinnamon, &c., frequently disagree with invalids. Sometimes milk or butter is added. Embden groats require less boiling than the common groats. Of oatmeal, the Scotch is commonly said to be the best.

The following directions for making gruel from oatmeal are given by Dr A. T. Thomson: “Oatmeal, 2 oz.; cold water, 1⁄2 pint; rub the meal in a basin, with the back of a spoon, in some of the water, pouring off the fluid after the grosser particles have subsided, but whilst the milkiness remains; repeat this with fresh water, unite the washings, and boil until a soft, thick mucilage is formed.”

GUA′IACIN. Syn. Guaiacic acid, Pure guaiacum resin. A substance having the nature of an acid, discovered by Trommsdorff in the wood and bark of Guaiacum officinale.

Prep. The tincture of guaiacum is treated with hydrate of lime, and the guaiacate of lime thus formed is decomposed with dilute sulphuric acid; it is purified by dissolving it in alcohol.

Prop., &c. Insoluble in water; soluble in alcohol and ether; it unites with the caustic alkalies, forming alkaline guaiacates (guaiacum soaps); air and light turn it green; gluten, mucilage of gum Arabic, &c., turn it blue; nitric acid and chlorine turn it successively green, blue, and brown; tincture of guaiacin, added to hydrocyanic acid and sulphate of copper, produces an intense blue colour. (Pagenstecher.) A delicate photographic paper may be formed by washing unsized paper with an alcoholic solution of guaiacum resin, and afterwards with one of neutral acetate of lead. (Johnston.)

GUA′IACUM. Syn. Guaiac, Gum guaiacum, Guaiacum resin; Guaiacum (Ph. L.), (Guaiac resin, Guaiaca resina, B. P.). The resin prepared by means of fire from the wood of Guaiacum officinale, by natural exudation, by incision, or by heat. (B. P.) This substance is often adulterated. When pure, its “fresh fracture is red, slowly passing to green; the tincture slowly strikes a lively blue colour on the inner surface of a thin paring of raw potato.” (B. P.) Adulteration with resin may be generally discovered by the odour evolved when the guaiacum is heated. An alcoholic tincture of guaiacum, rendered milky with water, recovers its transparency on the addition of caustic potassa in excess; but this is not the case when resin is present.

Guaiacum is stimulant, sudorific, and alterative.—Dose, 10 to 30 gr., either in powder or pills; in chronic rheumatism, gout, obstinate chronic skin disease, scrofula, syphilis, &c. It forms the active ingredient of the once celebrated ‘Chelsea Pensioner,’ and the ‘GOUT SPECIFIC’ of Mr Emerigon. The latter was made by digesting 2 oz. of guaiacum resin in 48 fl. oz. of rum, for seven or eight days. The dose of this was a table-spoonful every morning, fasting, for a twelvemonth. Its other properties are similar to those of GUAIACIN, but are less marked. Sp. gr. 1·20 to 1·22.

Guaiacum Wood. Syn. Lignum vitæ, Guaiaci lignum (Ph. L.), L. The wood of Guaiacum officinale. This is employed under the form of shavings, raspings, and sawdust, in decoctions only. See Decoction and Balsam.

GUA′NO. Syn. Huanho, Peruv. This substance, now so extensively used in agriculture, is the partially decomposed excrement of certain aquatic birds, chiefly the common penguin, which congregate in countless numbers on the barren and uninhabited islets and rocks on the western coasts of South America and the coasts of Africa. It abounds in ammonia and the phosphates, and is undoubtedly the richest natural manure known. Under judicious application the increase of the crops of grain, turnips, potatoes, and grass consequent upon its use is said to be about 33%. “Guano is peculiarly adapted to horticultural and floricultural improvement, by its relative cleanliness and facility of application.” (Ure.)

“According to Denham Smith, South American guano, as imported, presents itself in three distinct states, the three varieties being not unfrequently mixed together in the same bag; the first variety is damp and pulverulent; the second exists as large concretions, presenting various aspects when broken; the third is heavy and crystalline, and is termed ‘stone’ by the labourers. These three varieties differ widely in composition, as the following comprehensive analysis, by Smith, will show:—

Soluble in Water.

I. Pulverulent. II. Concrete. III. Saline.

Water 222·00 250·00 97·00

Chloride of ammonium 25·50 — 30·30

Sulphate of potash 80·00 — —

Sulphate soda traces 258·44 191·77

Oxalate of ammonia 74·00 93·90 —

Oxalate soda — — 105·63

Phosphate of ammonia 63·30 61·24 —

Phosphate potash — 77·32 49·47

Phosphate soda 1·20 — 3·60

Chloride of sodium — 29·22 286·31

Chloride of potassium — — 41·63

Organic matter 15·00 6·68 25·53

Urate of ammonia 154·18 — —

Uric acid 25·16 — —

Ammonia phosphate of magnesia 5·64 7·84 1·33

Animal matter 11·80 8·60 7·56

Insoluble in Water.

I. Pulverulent. II. Concrete. III. Saline.

Oxalate of lime 25·60 109·58 —

Phosphate of lime 199·30 62·70 132·23

Phosphate of magnesia 20·30 8·74 25·80

Oxide of iron — — 1·56

Humus and organic matters 60·92 8·00 18·36

Sand 15·60 7·20 4·20

Loss ·50 10·54 7·78

1000·00 1000·00 1000·00

“Several of the South American guano beds are now exhausted, but new varieties are constantly being introduced; and although the qualities are continually varying, guanos, on the whole, may be divided into two classes, the one characterised by the abundance of ammonia, the other by that of phosphates, the Peruvian and Angamos being characteristic of the former, and the Saldanha Bay and Bolivian of the latter. In selecting a guano, the following points (Anderson) ought to be attended to by the farmer:—

“1st. The guano should be light coloured and dry, colouring very slightly when squeezed together, and not gritty.

“2nd. It should not have too powerful an ammoniacal smell, and should contain lumps which, when broken, appear of a paler colour than the powder.

“3rd. A bushel should not weigh more than from 56 to 60 pounds.

“These characters are, however, imitated with great skill, so that they cannot be implicitly relied upon, and they are applicable to Peruvian guano only.”

Purity, Adulteration. Guano, owing to its high price, is very commonly adulterated, or is in an advanced stage of decomposition when sold. Much of what is vended under the name is altogether a fictitious article. These artificial mixtures are made to look so like genuine guano, that the mere practical man, who goes only by their appearance, is very often deceived by them, and, owing to the failure of his crops in consequence, is led to distrust the efficacy of guano as a manure. A sample of pretended guano examined by Johnstone was found to contain, in the state in which it was sold, more than half its weight of gypsum, the rest being peat or coal ashes, with a little common salt, crude sulphate of ammonia, and either dried urine or the refuse of the glue manufactories, to give it a smell. “I could not satisfy myself that it contained a particle of real guano.” Vessels which sail hence for the guano stations are now very commonly ballasted with rough gypsum or plaster of Paris. This substance is mixed with the guano as it is loaded, and enables the importers to deliver from the vessel a “nice-looking, light-coloured article.” Purchasers of guano are very desirous of having it delivered from the vessel, as they believe they thus obtain it pure. The favourite material for the adulteration of guano, at the present moment, is a variety of umber, which is brought from Anglesea in large quantities. The rate of admixture is said to be about 15 cwt. of umber to about 5 cwt. of Peruvian guano, from which an excellent-looking article is manufactured, which is sold under the name of ‘African guano.’

Pure guano has a pale-brown colour, a more or less offensive odour, and the average sp. gr. of 1·63 to 1·64. If the sp. gr. exceed 1·75, it is either damaged or adulterated; and if it is less than 1·62, it contains an undue quantity of moisture. The best is neutral to test-paper, and sometimes has even an acid reaction; but that of commerce has generally an alkaline reaction, owing to the presence of free ammonia, and, in consequence, turns turmeric paper brown, and gives white fumes when a glass rod dipped in hydrochloric acid is held over it. Triturated with quicksilver or caustic potassa, good guano evolves a powerful odour of ammonia; digested in water, fully one half of it is dissolved; dried by the heat of boiling water, it does not lose more than from 7 to 9% in weight; and burned upon a red-hot shovel, it leaves a white ash, not a red or dark-coloured one. (See directions for selecting guano given above, also below.)

Analysis or assay. The quantitative analysis of guano, so as to exhibit the names and proportions of all its numerous component substances, is an extremely tedious and difficult matter in the hands of persons unaccustomed to chemical manipulations. As, however, its value to the agriculturist depends chiefly on its richness in ammonia, potassa, and phosphoric acid, the analysis of guano for practical purposes may be reduced to an assay for these articles. Indeed, the presence of ammonia (the most valuable of them), in the proper quantity, may be fairly taken as evidence of the presence of the rest. The following methods of testing guano are both simple and accurate, and are so arranged as to permit its per-centage richness in one or more of its leading constituents to be determined without much trouble or expense.

1. a. 100 gr. of the sample for examination (fairly selected) are crushed to a powder, and placed on a small, weighed, and perfectly dry paper filter, and then desiccated, by exposure for 2 or 3 hours to the heat of boiling water. The loss in weight, taken in grains, after deducting 9, indicates the quantity per cent. of water or moisture which the sample contains in excess of that present in good or pure guano.

b. The paper filter, with its contents, is next suspended for some time over concentrated sulphuric acid (oil of vitriol) contained in a wide-mouthed bottle or jar, by means of a thread attached to the cork or stopper, care being taken to exclude the external air. The exposure in this way is continued until the guano ceases to diminish in weight, which is ascertained by weighing it at intervals after the first 3 or 4 hours. When this point is arrived at, the filter and its contents are very carefully weighed. The difference between its present weight and its original weight (before the desiccation in a), taken in grains, gives the gross quantity of water per cent.

c. The dried guano from b is next placed in a weighed, smooth crucible or capsule, and exposed to a low red heat until all the organic matter is completely destroyed, and the whole is reduced to a white ash, which is weighed as soon as it has become cold. This weight, in grains, gives the gross weight per cent. of non-volatile matter (fixed alkaline and earthy chlorides, phosphates, and sulphates); the total loss of weight by combustion denotes the gross per-centage of combustible and volatile matter (urea, uric acid, ammoniacal salts, and organic matter). The latter should not be less than 55 to 60%.

2. a. A second 100 gr. of the guano, selected as before, is distilled along with about 75 gr. of fresh-slaked quicklime, and a little water, in a small matrass connected with a tubular, triple bulb-condenser, containing cold distilled water, and immersed in a basin of ice-cold water. (See engr.) The condenser is charged by plunging one of its extremities into the water, and sucking at the other, until the liquid reaches the level indicated in the margin. A very gentle heat only, cautiously increased, need be employed. After the process is over, the strength of the solution of ammonia found in the condenser is tested, either by taking its density in a small specific-gravity bottle, or by determining its saturating power in the manner described under Alkalimetry. This furnishes the per-centage of ready formed ammonia sufficiently accurate for all ordinary purposes, provided proper care is taken.

When extreme accuracy is required, the condenser is charged with a weighed quantity of dilute hydrochloric acid of a known strength, instead of water, and after the process is over, this is tested as before. The quantity of ammoniacal test-liquor (see Alkalimetry) now taken to saturate it, deducted from what it would have taken before the exposure in the condenser, gives the per-centage sought.

Another method, giving very accurate results, is to use a rather strong hydrochloric acid (sp. gr. about 1·13) for the condenser; after the operation is over, the contents of the latter are poured into a glass or porcelain capsule, a solution of bichloride of platinum is added, in excess, and the whole is then gently evaporated to dryness; the residuum is rubbed to powder, and exhausted with a mixture of two measures of alcohol and one measure of ether; the undissolved portion is next dried at a heat not exceeding 212° Fahr., and weighed. The weight, in grains, of the ammonia chloride of platinum thus obtained, multiplied by ·0763, gives the per-centage of ready-formed ammonia, as before. When hydrochloric acid is used for the condenser, a simple U-tube and beaker glass may be employed, if a bulb-condenser is not at hand. (See engr.) The advantages resulting from the use of acid instead of water for the condenser is, that with the former no ammonia can possibly escape being absorbed, whilst little care is required to keep the condenser cool.

b. 25 gr. of the guano are next weighed, and after being slightly moistened with a little dilute hydrochloric acid, are thoroughly dried by the heat of boiling water; the dried sample is then mixed in a warm unglazed porcelain mortar with 10 times its weight of a mixture of 2 parts of quicklime to 1 part of hydrate of soda (both quite dry). This mixture is introduced into a combustion tube of hard Bohemian glass, about 16 or 18 inches long, and ⁄4 of an inch in diameter (see engr.) The mortar is rubbed out with a little of the soda-lime mixture, which is also introduced into the tube with that already put there; a little plug of ignited asbestos is then loosely placed over the whole, and the tube is immediately connected with a tubular bulb-condenser, containing moderately strong hydrochloric acid, great care being taken that the joints are made air-tight, which may be determined by the operator sucking a few bubbles out of the apparatus. If, after suction, the liquid remains at a higher level in the furthest bulb (b), it is a sign that the connection is sound. This being done, heat is applied to the combustion-tube, by means of spirit-lamps; or, more conveniently, by means of the furnace now usually employed in organic analysis (see engr.) The tube is next gradually surrounded with red-hot charcoal, by shifting by degrees the screen (c), and adding more charcoal, so as to gradually expel the ammonia. The disengagement of gas should take place uninterruptedly, but not too rapidly, in order that the acid may not ascend into the combustion-tube and spoil the experiment. The non-condensable volatile matters which pass off furnish a key to the progress of the operation. The heat is at length increased to a full red. When gas ceases to be evolved, and the mixture in the tube has become quite white, the experiment is at an end. The point (a) of the combustion-tube is broken off, and the ammonia which remains in the tube is expelled by sucking gently at the extremity (b) of the bulb-condenser. The latter is then disconnected with the apparatus, and emptied into a glass or porcelain capsule, in order to be tested, as directed under 2, a. The quantity of ammonia, in grains, thus found, multiplied by 4, gives the WHOLE QUANTITY of AMMONIA per cent., both actual and potential, producible from the sample of guano examined.

c. The quantity of ready-formed ammonia (see 2, a) deducted from the quantity last found (see 2, b) gives the quantity of LATENT or POTENTIAL AMMONIA that will be slowly developed by the decomposition of the guano in the soil, and become available for the food of plants. This is the most valuable product of this substance as a manure, and can only be obtained in quantity from well-preserved, dry guano.

3. a. A third quantity of 100 gr. of the guano, selected as before, is triturated and digested for some time with 12 times its weight of hot distilled water, and the whole being thrown on a filter, the undissolved portion is washed with a little warm distilled water; the solution and ‘washings’ are then mixed together, and acidulated with nitric acid; a solution of pernitrate of iron is next added, and afterwards solution of ammonia, in excess; the liquid is next heated for a short time, and the bulky reddish-brown precipitate is collected, washed with hot water, dried, ignited, and weighed. The weight, in grains, less the weight of the peroxide of iron in the pernitrate consumed, gives the weight of PHOSPHORIC ACID present in the soluble phosphates contained in the sample. The pernitrate of iron is made by direct solution in hot strong nitric acid, of twice as much pure iron wire as there is phosphoric acid suspected to be present in the liquid. A slight excess will not alter the result. The number of grains of metallic iron used to form the solution, multiplied by 1·4286, gives the weight of the peroxide of iron which is to be deducted from the gross weight of the precipitate.

b. The filtrate and ‘washings’ left from 3 a are mixed, and treated with a little oxalate of ammonia to throw down any lime, and then carefully evaporated to dryness and ignited; the residuum of the ignition, when cold, after being carefully weighed, is treated with the smallest portion of water that will dissolve it; the solution is acidified with hydrochloric acid, and a solution of bichloride of platinum added, in excess; some strong alcohol is next poured in, the precipitate carefully collected on a filter, washed with rectified spirit, dried at 212° Fahr., and weighed. The weight, in grains, multiplied by ·1940, gives the per-centage of POTASSA sought.

c. The weight of the potassa multiplied by 1·852, and deducted from the weight of the ignited residuum in 3 b already found (see above), gives the quantity of CHLORIDE OF SODIUM or COMMON SALT (nearly).

4. a. The insoluble residuum from 3 a, dried, and ignited, or the ash from 1 c, is digested for 10 or 12 hours in 600 times its weight of water (to which a little common salt or sal-ammoniac may be added), after which the whole is thrown upon a filter; a solution of chloride of barium is then added to the filtrate as long as a precipitate (if any) forms; the latter is collected, washed, dried, ignited, and weighed. The weight, in grains, multiplied by ·5843, denotes the quantity of GYPSUM or SULPHATE OF LIME which has been used to adulterate the sample.

b. The insoluble residuum last left on the filter is digested for some time in warm dilute hydrochloric acid; the whole is then thrown upon a filter, and the undissolved portion (SILICA or SAND, with, perhaps, a trace of ALUMINA) is washed, dried, ignited, and weighed. It should not weigh more than 3 to 3⁄2 gr. (3 to 3⁄2%).

c. The filtrate and ‘washings’ from b are next mixed together; the mixed liquid is acidified with dilute sulphuric acid and heated until all the hydrochloric acid is expelled, and the whole reduced to a soft pasty mass; rectified spirit is now poured in, and after active stirring for some time, the mixture is thrown on a filter, and the solid portion washed with a little more rectified spirit; it is then dried, ignited, and weighed. The weight, in grains, multiplied by ·7650, gives the quantity of PHOSPHATE OF LIME per cent. required.

d. The filtrate from c is diluted with water, and after being boiled for a few minutes, ammonia is added in slight excess, followed by a solution of sulphate of magnesia (previously mixed with as much sal-ammoniac as will prevent ammonia producing a precipitate in it), slowly dropped in as long as it disturbs the liquor; the whole is now allowed to rest for 10 or 12 hours, when the precipitate is collected on a filter, and washed with water alkalised with ammonia, as long as the filtering liquid is rendered turbid by chloride of barium; it is next dried, submitted to intense ignition for some time in a covered platinum crucible, and, when cold, carefully weighed. The weight, in grains, multiplied by ·6429, indicates the per-centage of PHOSPHORIC ACID in the insoluble phosphates (phosphates of lime, magnesia, &c.) in the sample examined.

5. A fourth 100 gr, of guano is weighed, and exhausted by trituration and digestion with hot water (see 3 a); the solution is evaporated to dryness by a gentle heat, and the residuum of the evaporation, after being weighed, is powdered and enclosed in a stout phial with 8 times its volume of alcohol, sp. gr. ·825 (63 o. p.); the plant is next securely corked and guarded, and exposed for some time, with agitation, to the heat of 212° Fahr., the whole is then allowed to cool, the contents of the phial filtered, the undissolved portion washed with hot alcohol, and both the filtrate and the ‘washings’ gently evaporated to dryness, and weighed. This gives the richness of the sample in UREA, one of the most valuable constituents of the best guano. Its presence is “a certain proof of its entire soundness.” (Ure.)

6. a. Another 100 gr. of the guano is taken, and, after being exhausted with water, is dried at 212° Fahr., and weighed; it is then digested with heat in 20 times its weight of borax-water (containing 1% of borax), or in a solution of caustic potassa, and after a time the whole is thrown on a weighed filter, washed with a little cold distilled water, dried by a heat not higher than that of boiling water, and again carefully weighed. The loss, in grains, indicates the proportion per cent. of URIC ACID.

The accuracy of the result may be verified by adding dilute hydrochloric acid, in slight excess, to the filtrate, collecting the bulky, crystalline precipitate of uric acid which forms, washing it carefully with a little rectified spirit, drying it, and weighing it, as before. This weight, which in general is a very little under that denoted above, is the more accurate of the two. The precipitate is shown to be uric acid by its assuming a rich crimson colour when treated with a little nitric acid, which turns to a rich purple (murexide) when it is moistened with ammonia water.

b. The quantity of uric acid last obtained, multiplied by 1·1012, gives the per-centage of URATE OF AMMONIA.

Obs. Amongst the numerous constituents of guano, none are so valuable in an agricultural point of view as the three substances referred to in the last two sections. Indeed, almost all the ammonia furnished by this substance to the soil, after the latter, manured with it, has been exposed to the air and rain, is derived from the slow decomposition of urea, or urate of ammonia. It is these substances from which the store of latent, or, as Dr Ure terms it, potential ammonia, is derived. The ammonia existing in the guano under the form of carbonate, or of soluble salts (ready formed ammonia), is either soon dissipated in air or is washed away by heavy rains, and, therefore, forms the least valuable and durable portion of this manure. It may be even added artificially, a matter almost impossible with the former. An assay, therefore, for the latent ammonia, or the urea, or the urate of ammonia, any one of them singly, at once furnishes us, as we have already hinted, with evidence of the quality of the guano examined, without the expense and trouble of a complete analysis of this substance. Urea and uric acid are only to be found in the very best samples of guano, and their presence is a positive proof of entire soundness and superior quality. The other valuable portions of guano are potassa and phosphoric acid (phosphate of lime chiefly); the rest are of little importance. (See 2 c, above.)

GUARANA (Grimault & Co., Paris). 12 migrain powders, each weighing 1·75 grammes, consisting of guarana, but perhaps also containing an admixture of cocoa seeds, neither prepared nor roasted. (Hager.)

GUARANA′. Syn. Paullinia, Brazilian cocoa. An alimentary and medicinal substance prepared from the seeds of Paullinia sorbilis, a Brazilian tree. The dried seeds, deprived of their aril, are pounded and kneaded into a mass, which is afterwards made into oblong or rounded cakes (GUARANA BREAD). These cakes are used as we use chocolate—mixed with water and sugar, and drank as a beverage. In Brazil this beverage is largely consumed, both on account of its nutritive qualities, and for its stomachic, febrifugal, and aphrodisiac effects. See Chocolate, &c., also below.

GUARANINE′. A crystalline substance discovered by M. Martius in guarana. It appears to be identical with caffeine, the active principle of coffee and tea.

GUD′GEON. The Cyprinus gobeo (Linn.), a small fresh-water fish, common almost everywhere. The white is considered the best. It was formerly used in medicine.

GUM. Syn. Gummi, L. The general term for an important class of vegetable products. Gums are more or less soluble in cold water, but insoluble in alcohol, ether, and oils. They are obtained from certain plants in amorphous masses; most of them exude spontaneously, or on puncturing the bark. The most perfect type of this class is the substance called GUM ARABIC, or GUM ACACIA. The gums are employed as demulcents in medicines, and are used as cements, and for giving stiffness and gloss to textile fabrics. Among the vulgar the term is often incorrectly applied to the resins and gum resins.

Gum Acacia. Syn. Gum Arabic; Acaciæ gummi (B. P.); G. arabicum, G. acacia, Acacia (Ph. L.), L. “From various species” (of Acacia) “yielding gum” (Ph. L. & E.), chiefly Acacia arabica and A. vera. “Whitish or yellowish, transparent or cracked on the surface, and opaque; brittle; it dissolves freely in water.” (Ph. L.) It is scentless, and may be bleached by exposure to the sun and air, at the temperature of boiling water. Sp. gr. 1·355. (Ure.) The pure soluble principle of gum Arabic is termed ARABIN (which see). Barbary or Morocco gum, Gum Senegal, and East India gum, are inferior commercial varieties of the same substance from other species of Acacia (see below).

Powdered gum Arabic (PULVIS ACACIÆ) is frequently adulterated with flour or farina, or with Senegal or other inferior gums. The first may be detected by agitating a little of the powder with cold water; the pure gum dissolves rapidly, whilst the starch or flour falls to the bottom of the vessel. Or, a little of the powder may be mixed with boiling water, and when cold, tested with tincture of iodine; if it contains starch or flour, the paste will assume a blue colour. If it contains cherry-tree gum or tragacanth, it will be only partly soluble in cold water, and the paste will be partly coloured, and more or less interspersed with gelatinous clots.

For the detection of dextrin in gum Arabic Hager finds that when some of the adulterated article is placed in a glass dish, with vertical sides, and a solution of ferric chloride, density 1·48, diluted with an equal volume of water, is poured over it until the grains are just covered, in the course of a minute or so that particles of gum Arabic will adhere to the bottom of the vessel, whilst the grains of dextrin do not.

Much of the white gum Arabic of the shops is formed by bleaching gum Senegal, by what is called ‘Picciotto’s process.’ The gum is dissolved in water, and sulphurous acid gas passed through the solution. The liquid is afterwards boiled to expel the sulphurous acid, a little of which, however, still remains behind. To obtain the gum in a still whiter state, carbonate of baryta is added, and after agitation the mixture is filtered; it is afterwards shaken with gelatinous alumina, again filtered, and evaporated. The product (BLEACHED GUM) is very white, but lacks the peculiar toughness and adhesiveness of the best gum acacia.

Gum, Barbary. Syn. Morocco gum. An inferior product, consisting of a mixture of several Acacia gums. It is exported from Mogador.

Gum, Bassora. A solution of yellowish gum brought from the neighbourhood of Bassora. It differs from most gums in being nearly insoluble in water. The plant yielding it is believed to be a species of Mimosa. It contains the principle BASSORIN, which also exists in gum tragacanth.

Gum, Bleached. See Gum Arabic (above).

Gum, Brit′ish. Syn. Dextrin, Starch gum. Starch converted by the action of acids, diastase, or heat, into a soluble substance resembling gum.

Prep. 1. Malt (crushed small), 1 lb.; warm water, 2 galls.; mix, heat the whole to 145° Fahr., add of potato starch 5 lbs., raise the heat to 160° or 165° Fahr., and mash for about 25 minutes, or until the liquid becomes thin and clear; it must then be instantly run off, and raised to the boiling point to prevent the formation of sugar; after boiling for 3 or 4 minutes the whole must be filtered, and evaporated to dryness by a steam heat.

2. By exposing dry potato starch, in a stove, to a heat of about 400° Fahr. Yellow and inferior.

3. (M. Payen.) Dry starch, 1 ton, is moistened uniformly with concentrated nitric acid, 4⁄2 lbs. (diluted with), water, q. s., and the paste or dough is made up into small bricks or loaves, and dried in a stove; it is next reduced to coarse powder, and exposed in a stove-room for some time to a current of air at 160° to 165° Fahr.; it is next ground, sifted, and exposed, as before, to a heat of about 228° Fahr.; it is, lastly, ground, and passed through the ‘bolting machine.’ Very white and superior. This process has been patented in France by M. Henzé.

4. (Pinel.) Water, 100 galls., nitric acid, ⁄2 gall., and hydrochloric acid, ⁄2 pint, are mixed together, and so much potato starch is mixed as will form a thin paste; in two hours the liquid is drained off, and the solid matter is made up into lumps, which are dried by a gentle heat in a stove-room; they are next coarsely pulverised, and the powder is exposed on three successive days to the respective temperatures of 100°, 150°, and 190° Fahr.; the whole is then sifted, and, lastly, exposed to a heat ranging from 300° to 350° Fahr. Darker coloured than the last. To give it the appearance of gum Arabic, it is made into a paste with water containing 1% of nitric acid, and after being spread on copper plates in layers ⁄4 to 1 inch thick, it is exposed to a stove heat ranging from 240° to 300° Fahr.

Prop., &c. White; insipid; transparent; friable; soluble in cold water, and in dilute spirit; insoluble in alcohol and ether; its solution yields a precipitate with acetate of lead. Iodine commonly turns commercial dextrin blue, but does not affect the colour of pure dextrin. It is distinguished from ordinary gum by its right-handed polarization of light, and by yielding oxalic but not mucic acid, when treated with nitric acid.

Dextrin is nutritive, emollient, and agglutinant. In France it is largely employed by the pastry-cooks and confectioners, and in medicine as a substitute for gum. The French surgeons also commonly employ it as a ‘stiffening’ for the splints used for fractured limbs. In this country it is chiefly used as a fine dressing for muslins, silk, and other textile fabrics, and in calico printing. Recently it has been made up into tear-like masses, and sold for gum Arabic, to which, however, it is vastly inferior as an agglutinant. See Dextrin.

Gum, Cherry-tree. Syn. Fruit-tree gum, Plum-tree g.; Gummi cerasi, G. pruni, L. An exudation from the stems of cherry, plum, and some other of the Rosaceæ. It is only partly soluble in water. It contains CERASIN (which see).

Gum, East India. This product, which consists of inferior kinds of gum acacia, is chiefly exported from Bombay, having been previously conveyed there from the coast of Arabia. It varies greatly in quality. Some samples are quite unfitted for making gum-water.

Gum, Insoluble. See Bassora Gum, Cherry-tree Gum, and Gum Tragacanth.

Gum, Seed. Syn. Gummi seminum, L. A species of soluble gum extracted from the seed of the flax (linseed), quince, &c.

Gum, Senegal. This product, which is largely exported from Portendie, Sierra Leone, and the French settlements on the Senegal, ranks next in quality to gum acacia, and for many purposes, as calico-printing for instance, it answers equally well. The transparent and light-coloured pieces are frequently picked out and sold as gum Arabic.

Gum Trag′acanth. Syn. Tragacanth, Gum dragon; Gummi tragacantha, G. draconis, Tragacantha (Ph. L.), L. The gummy exudation of the Astragalus verus, hardened by the air. When digested in water, it swells considerably, a portion is dissolved, and the whole combines to form a thick mucilage. It is totally soluble in boiling water, when some change is supposed to take place in it; a great portion, however, afterwards separates. Sp. gr. 1·384. It is chiefly employed in calico-printing, and by shoemakers and lozenge-makers; by the latter to give toughness to the saccharine mass.

Powdered tragacanth is often adulterated with flour of starch, and not unfrequently with the commoner varieties of gum Arabic. According to M. Planche, a mixture of pulverised tragacanth and gum Arabic forms, with water, a thinner mucilage than the same quantity of either of these gums alone. This fraud may be detected as follows:—Make a mucilage of the suspected gum, and add thereto a few drops (2 or 3 to the dr.) of alcoholic tincture of guaiacum, taking care to stir it all the while. If the sample contains any gum Arabic, the mixture, in the course of a few minutes, assumes a fine blue colour, whilst it does not change colour if the gum tragacanth is pure, 5% of gum arabic can be thus detected. When the quantity is very small, one to four hours may elapse before the colour is developed. Starch and flour are detected in the manner noticed under Gum Arabic.

Gum, Turkey. Various qualities of gum acacia are sold under this name.

GUM RES′INS. Syn. Gummi resinæ, L. Vegetable products in which the properties of gum and resin are combined. They are partly soluble in water, and partly in alcohol. Many of them form a species of emulsion when triturated with the former fluid. The principal gum resins are AMMONIACUM, ASSAFŒTIDA, BDELLIUM, GALBANUM, GAMBOGE, MYRRH, OLIBANUM, OPOPONAX, SAGAPENUM, and SCAMMONY.

GUN BAR′RELS. See Browning.

GUN COT′TON. See Pyroxylin.

GUN MET′AL. An alloy containing 90·5% of copper and 9·5% of tin, used for casting pieces of ordnance (erroneously termed ‘brass guns’), also those parts of machinery which are subjected to considerable friction. See Alloys, Bronze, Stereo-metal, &c.

GUN′POWDER. This substance is a mechanical mixture of saltpetre, charcoal, and sulphur. It is seldom prepared on the small scale.

Prep. The saltpetre having been trebly refined, by boiling, skimming, filtering, and crystallising, is melted into cakes, which are then brushed to remove any adhering grit or dirt, broken into pieces with a mallet, ground to a fine powder in a mill, and sifted through a fine bolting sieve of brass wire. The charcoal is that of the alder or willow, and is carefully burnt, as already described, and is then reduced to powder. The sulphur is refined by distillation, and ground to the same fineness as the charcoal and saltpetre. The ingredients are weighed out in the proper proportions, and mixed together in a machine consisting of a wooden drum, having a shaft passing through its centre, to which numerous ‘flyers’ in the shape of knife-blades are attached, the drum and flyers revolving in a contrary direction. When mixed, the charge is carried to the ‘incorporating mill,’ where it is ground under vertical iron ‘mill-stones,’ with a small quantity of distilled water, until the ingredients are thoroughly incorporated. The product of this operation is then pressed into a hard cake, which is next broken into pieces, granulated by means of sieves, and after being ‘glazed’ by friction, and the dust separated, is dried, with proper precautions, in a stove heated to about 130° by steam pipes.

The proportions of saltpetre, charcoal, and sulphur, used for different kinds of powder, differ very slightly. In ‘sporting powders’ the proportion of saltpetre is generally from 1 to 3% greater than in the Government powders. In ‘miners’ powders’ it is about 10% less, an excess of sulphur being used. The following are the proportions adopted by European powers:

Saltpetre. Charcoal. Sulphur.

England 75 15 10

France 75 12·5 12·5

Austria 75 15 10

Prussia 75 13·5 11·5

Russia 73·78 13·59 12·63

Spain 76·47 10·78 12·75

Sweden 76 15 9

(Capt. Jervis-White Jervis.)

Obs. The quality of gunpowder is best estimated by actual trial of its power and cleanliness in use. It should be dry, hard, and free from dust; the grains should be of a uniform size, and glossy, and the colour a dark-grey or brownish-grey, not perfectly black. A very little placed on a piece of paper and fired should instantly explode with a flash, and neither leave an appreciable residue on the paper nor burn it. Dried by the heat of boiling water, or in vacuo, it should not lose more than ⁄2 to 1% of its weight. Damp powder rapidly ‘fouls’ the gun. Gunpowder, containing more than 7% of water, does not recover its strength by simply drying it. The sp. gr. ranges between 1·795 and 1·800.

Karolyi succeeded in analysing the gases of gunpowder which had been fired in conditions closely resembling those which occur in artillery practice. For this purpose he enclosed a charge of powder in an iron cylinder of such strength that it just burst when the powder was fired by means of the electric spark. This charged cylinder was suspended in a hollow spherical bomb, from which the air was exhausted before firing.

After the explosion had been produced, the gases and the solid residue of the powder were submitted to analysis. The results obtained were the following:

1. Composition of the Powder used.

Ordnance Powder. Small Arms Powder.

Nitre 73·78 77·15

Sulphur 12·80 8·63

Charcoal. Carbon 10·88 11·78

Hydrogen 0·38 0·42

Oxygen 1·82 1·79

Ash 0·31 0·28

99·97 100·05

2. Products of Combustion by Weight.

Ordnance Powder. Small Arms Powder.

Gaseous. Nitrogen 9·77 30·58 10·06 34·18

Carbonic anhydride 17·39 21·79

Carbonic oxide 2·64 1·47

Hydrogen 0·11 0·14

Sulph. hydrogen 0·27 0·23

Marsh gas 0·40 0·49

Solid. Ammonic sesquicarbonate 2·68 69·25 2·66 65·14

Potassic sulphate 36·95 36·17

Potassic carbonate 19·40 20·78

Potassic hyposulphite 2·85 1·77

Potassic sulphide 0·11 0·00

Charcoal 2·57 2·60

Sulphur 4·69 1·16

Loss. 0·17 0·68

100·00 100·00

3. Products of Combustion by Volume in 100 of Gas.

Ordnance Powder. Small Arms Powder.

Nitrogen 37·58 100 35·33 100

Carbonic anhydride 42·74 48·90

Carbonic oxide 10·19 5·18

Hydrogen 5·93 6·90

Sulphuretted hydrogen 0·86 0·67

Marsh gas 2·70 3·02

It will be seen from the above figures that in addition to the generation of a considerable amount of carbonic anhydride (carbonic acid) by the combustion of gunpowder, there is liberated at the same time a large quantity of solid matter, in the form of sulphate and carbonate of potash, sulphide of potassium, sulphur, charcoal, &c. This will explain why the air of mines is so prejudicial to the health of the miner, particularly when he is engaged in blasting operations, these being carried on in a more or less confined space. See Air, vitiated.

Gunpowder, Schultze. The subjoined account of Schultze gunpowder is a transcription of a report communicated to the editor of the ‘Field’ newspaper by Mr F. Toms, A.I.C., F.C.S. After referring to a previous communication on the same subject Mr Toms proceeds as follows:—I have carried out some further experiments, with the aid (by Dr Frankland’s kind permission) of apparatus more suited to my requirements than that previously at my disposal; and I now proceed to lay before you the results of these experiments, and the conclusions to which they have led me, respecting the powders formerly received and the new Schultze powder, with a sample of which you have since favoured me.

The main constituent of the Schultze gunpowder, as you are aware, is wood fibre, which, having first been purified, is then subjected to the action of strong nitric acid (intensified by mixture with sulphuric acid), and thus is converted into a kind of nitro-cellulose or pyroxylin, the ordinary form of which is gun-cotton. The wood fibre undergoes no change in appearance by this treatment; but a change takes place in its chemical composition, which may thus be exemplified:

Cellulose (unconverted
cotton or wood fibre). Nitro-cellulose (cotton or wood
fibre treated with nitric acid).

Carbon 6 parts 6 parts.

Oxygen 5 parts 5 parts

Hydrogen 10 parts 7 parts or more.

Nitroxyl (NO2) none 3 parts or less.

It will thus be seen that the sole difference between gun-cotton or Schultze powder and ordinary cotton or wood fibre is, that some of the hydrogen is abstracted and has its place supplied by nitroxyl—a substance contained in nitric acid, and composed of one part of nitrogen united with two parts of oxygen. Under the most favorable circumstances, it is possible to replace three of the ten parts of hydrogen by three of the nitroxyl, when the substance produced is explosive, and is called from its composition tri-nitro-cellulose. This is the purest form of gun-cotton. If weaker acid is used, less hydrogen is displaced, and the product is called di-nitro-cellulose or mono-nitro-cellulose, according as it contains two or only one part of nitroxyl. These derivatives are either feebly explosive or not explosive at all. Such are the compounds known as photographic collodion and soluble gun cotton—the latter name distinguishing it from pure gun-cotton, which is not soluble in a mixture of ether and alcohol.

The Schultze powder contains both the explosive and the non-explosive varieties of nitro-cellulose.

If the wood fibre, after being carefully purified according to the method described in Schultze’s patent of 1864, were thoroughly desiccated and allowed to cool out of contact with air, and then dipped in acid of the strength mentioned in the specification, there seems no theoretical reason why an explosive powder containing at least 90% of true tri-nitro-cellulose should not be produced. As, however, I find on experiment that nothing like that per-centage is arrived at, I can only conclude that, in order to moderate the violence of the explosion, the Schultze Company secure the formation of a large per-centage of “soluble” or less explosive nitro-compounds by merely air-drying their wood.

If this supposition be generally true, it seems probable that the sample of Schultze powder supplied by Messrs Blissett may owe its extra explosive force to exceptional care being taken, during the interval between the drying and the dipping, to prevent the absorption of moisture—with the addition, perhaps, of an increased length of exposure to the action of the acid.

That some such variation of the ordinary procedure was carried out seems evident from the different proportions of soluble and insoluble gun-cotton in the specimens of Schuitze powder supplied by Messrs Blissett and Messrs Bland; for it was found that on the washed wood fibre from each being submitted to the action of a mixture of alcohol and ether, about one half of the former powder and two thirds of the latter were dissolved out. This shows that while the “Blissett” specimen contained about one half its weight of insoluble or explosive nitro-cellulose, the “Bland” contained only about one third—a difference which confirms the result obtained by analysis as stated below.

The soluble gun-cotton, ordinarily non-explosive, may, however, be rendered explosive by saturating it with bodies rich in oxygen, which promote the decomposition and complete the combustion of the fibre. Nitre is used for that purpose, because it parts with its oxygen readily; and nitrate of baryta is also used, because, being more stable than the nitre, it renders the combustion more gradual than would be the case if nitre were alone employed. When both are used, the nitre, I should think, would start, and the nitrate of baryta continue and finish the combustion of the powder. The amount used is, I suppose, the result of calculation and experiment; but a powder containing little true tri-nitro-cellulose should require more of these salts than one containing much tri-nitro-cellulose; and an excess of the salts would lower the rate of burning of the powder.

I will now give my analysis in full of the three powders, viz.—(1) the ordinary powder issued last season, being part of a supply obtained from Messrs Bland, gunmakers, of the Strand; (2) some powder furnished by Messrs Blissett, of Holborn, and alluded to in their letter in the ‘Field’ of Jan. 19th last, as having damaged a gun made by them; and (3) some of the new powder of 1878, as used at the ‘Field’ trial of explosives in May last.

1877 Bland’s. Blissett’s. 1878 Trial or New.

Moisture, per cent. 2·18 2·39 2·97

Extracted by water. Nitrate of baryta, per cent. 21·50 16·59 22·32

Nitrate of potash, per cent. 11·46 10·46 6·47

Yellow coloured organic substance, trace of chlorides, &c., undetermined

Insoluble in water. The converted wood fibre (nitro-cellulose) then remaining contained the following per-centage of mineral matter 5·0 6·0 2·95

The converted wood fibre (after allowing for extraneous mineral matter) possessed the following per-centage composition. I place for comparison Professor Abel’s determination of the composition of tri-nitro-cellulose, and two of the impurities found along with it, in a parallel column.

Bland’s. Blissett’s. Trial or New. Tri-nitro-
Cellulose. Impurities.

Carbon 28·75 28·07 28·12 24·24 29·20 30·50

Hydrogen 3·49 3·65 3·54 2·36 — 2·91

Nitrogen 10·80 15·60 11·66 14·14 11·85 —

Oxygen 56·06 52·68 56·68 59·26 — —

These powders exploded at a temperature of about 190° C. (374° F.), the different samples varying but slightly. Pure gun-cotton is stated by Professor Abel to explode at 150° C. (302° F.); and black powders are said, by different authorities, to explode at various temperatures between 500° and 600° F., according to the variation in their composition and manufacture.

In addition to the difference in chemical composition of these Schultze powders, I would point out that there is a difference in density—the Blissett being heaviest, the Bland next, and the New the lightest of the three. I think this fact also has some bearing on the violence of the explosion. In black powders, I believe, a dense powder, speaking generally, is stronger than a lighter one; and the Schultze patent states that hard woods make more explosive powders—not, I take it, because the composition is thereby altered, but because a denser powder is produced. It would appear to me, from the above analyses, that the new trial powder should contain rather more explosive force than the Bland variety, though considerably less than the Blissett. The result may, however, be modified by the difference in density of the powders; and your practical experiments will show how far this agrees with the results of the shooting.

I have hitherto only spoken of the explosive force of the powder; now I will touch on another point—its tendency to spontaneous decomposition. Knowing that, in the case of gun-cotton, its stability is injured by a small proportion of resin and other organic impurities, and by the presence of free mineral acids. I did not expect to find this powder (made from a less pure kind of cellulose, from which also it must be somewhat difficult to wash all traces of acid) equal in stability to gun-cotton; and on subjecting the three kinds of Schultze powder to the Government ‘heat test’ of 150° F. (with a minimum of 10 minutes’ duration), it was found that the

New or Trial (1878) Powder stood the test 12 m.

‘Bland’s’ sample stood the test 8 m.

‘Blissett’s’ sample stood the test 7 m.

This shows that the ‘new’ powder is very stable, as it stood the test for two minutes beyond the Government minimum, while the other two samples were a good way below it. The officials at Waltham Abbey would accept no gun-cotton which did not stand the test for ten minutes; and I have seen the best gun-cotton stand it for fifteen.

Whether the loose granulated condition of the Schultze powder, when stored, is sufficient to neutralise this inferiority in purity, and render a sample of Schultze, which only stands the test of seven minutes, as little liable to spontaneous combustion as gun-cotton which stands the test for ten minutes, there is at present no evidence to show.

To carry out this ‘heat test’ properly, some practice is required; so, in order to put the matter beyond doubt, I called in the assistance of my friend Mr Arthur Linnell, F.C.S., chemist to the Gun-Cotton Company, Stowmarket, a gentleman who uses the test daily, and who carried out the above three experiments strictly after the manner adopted by himself and by the Government officials.

In addition to Mr Linnell’s experiments, I noted that the aqueous extract of ‘Blissett’ was very faintly acid; that when heated in a chest at 195° F. moist blue litmus was very quickly reddened.

I think this serious defect (want of stability) is due to want of care in the washing; and I base this opinion on the following facts:

(1) The ‘Bland’ and ‘Blissett’ samples (the powders of least stability) are of a deeper tint than the ‘new’ (due to the soluble yellow impurity before mentioned). By continued washing in warm water they become pale, like the more carefully prepared new powder, and the yellow substance is dissolved away. Hence the lighter colour of the ‘new’ (and most stable) indicates it has less of this organic impurity.

(2) Sulphuric and nitric acids are used in the dipping of the powder, but should be entirely washed out, as they promote spontaneous decomposition. If left in, the sulphuric acid will, when the salts are added, decompose the nitrate of baryta, forming insoluble baric sulphate and free nitric acid.

On experiment I ascertained that the abnormally large quantity of mineral matter or ash (5 and 6 per cent.) found in the insoluble part of the ‘Bland’ and ‘Blissett’ powders is due to baric sulphate, and I think the acidity of the aqueous extract is due to the nitric acid thus set free.

Had this baric sulphate been present in the new powder, I should have thought it was purposely formed in all to prevent access of moisture; but, not finding this substance in this carefully prepared sample, I attribute its presence in the other cases to carelessness on the part of the workmen.

I should state that all these powders consisted of a granulated and consolidated pulp. This improvement must, I think, have considerable advantages over the sawdust form previously adopted by the Schultze Company in as much as it facilitates a more thorough purification being carried out, and produces a more homogeneous and equal powder. It is possible, too, that working with pulp may be of advantage, inasmuch as the company may now, by varying the pressure in forming the cake, obtain grains of any required density.

In conclusion, I may say that, in my opinion the most difficult task which the Schultze Company have had to encounter is that of obtaining uniformity of strength in their explosive; and the ‘Blisset’ sample of their powder may he looked upon as an experimental batch in which (by altering the mode of procedure in some such manner as I have indicated) they made a powder with a large per-centage of tri-nitro-cellulose, thus producing a more rapidly burning substance, and consequently a more violent explosion.

Taking all things into consideration, I think the Schultze Company, in manufacturing a nitro-explosive which gives the uniformity of shooting power shown in your recent experiments, have worked out a most troublesome problem with remarkable success. The difficulty of obtaining such results is evidenced by the fact that so many inventions of a somewhat similar character have been abandoned for sporting purposes from a deficiency in this respect.

But, however difficult it may be to manufacture a powder giving uniform shooting, it is evidently possible, with suitable care to produce (as the ‘new’ Schultze shows) a wood powder which is perfectly safe and stable, as far as spontaneous decomposition is concerned. The company, therefore, if they have not already done so, ought to take means to prevent powder of the low stability of the ‘Bland’ and ‘Blissett’ samples being again issued from their works.

P.S.—Since writing the above I have examined cursorily a sample of the ‘Dittmar’ wood powder, an American variety of ‘Schultze,’ used by Captain Bogardus in some of his recent shooting competitions. The powder is somewhat darker in tint, and of slightly larger grain, than the Schultze. In density it is intermediate between ‘Bland’s’ and the ‘new’ powder; and the charge in a twenty-bore cartridge was forty-two grains. This powder would seem to be made from solid cubes of wood (not a pulped mass like the present ‘granulated’ Schultze, or of sawdust splinters like the old so-called ‘cube’ Schultze). It contains no nitrate of baryta, but has a small quantity of nitrate of potash and soda. Possessing, as it would seem, therefore, a much smaller proportion of oxidizing salts than the English Schultze, it should contain, to make up for this loss of force, a larger proportion of explosive pyroxylin; but this is a point I have not experimentally determined. (‘Field,’ August 3rd, 1878, No. 1336, p. 143.)

Gunpowder, White. Syn. Blasting powder. Prep. 1. See Blasting Powder, No. 3.

2. Yellow prussiate of potash and white sugar, of each 1 part; chlorate of potassa, 2 parts; powder each separately, and mix them well, but carefully, with a bone or wooden knife. It may be granulated like gunpowder, by making the powder into a paste with a little water, and pressing the mass through a parchment sieve.

GUN′JAH. See Hemp (Indian).

GUT. Syn. Fishing gut, Silkworm g. This is obtained from the Bombyx mori (Linn.) or silkworm caterpillar. Prep. The silkworms, when just ready to spin, are steeped in strong vinegar for 12 hours in warm weather, or 2 or 3 in cold weather, and are then broken in half, and stretched out as far as possible on a board, furnished with slits or pegs to hold them; in this state they are allowed to dry in the sun or a warm place.

Obs. Used by anglers. The worms may be known to be going to spin by refusing food, and by having a fine silken thread hanging from the mouth.

GUT′TA PERCHA. The concrete juice of the Isonandro Gutta, a tree growing only in the Malayan Archipelago, and of other species of the same genus. The stem of the gutta-percha tree grows to the diameter of 5 or 6 feet, and on being notched yields a milky juice, which, after exposure to the air for some time, solidifies, forming the gutta percha of commerce. It arrives in this country in irregular blocks of some pounds in weight, usually containing a large portion of impurities in the form of pieces of wood, stones, and earth. To prepare this crude product for manufacturing into useful articles, the blocks are first cut into slices, and then torn into shreds. These are softened by hot water, and kneaded in a ‘masticator,’ the stones, earth, and other impurities, being gradually washed away by water. After several hours the gutta percha is found to be kneaded into a perfectly homogeneous mass, which is rolled or drawn into sheets, bands, or tubes, as required.

Prop., &c. Gutta percha is a tough, inelastic substance, becoming soft and plastic at 212° Fahr., at which temperature two pieces may be firmly welded together. It is one of the best insulators of electricity, is impervious to moisture, and resists the action of acids and alkalies to a great extent. Its best solvents are benzol, chloroform, bisulphuret of carbon, rectified mineral naphtha, and rectified oil of turpentine. All these dissolve it readily. According to the analysis of Payen, the purified gutta percha of commerce consists of 75 to 828 of chemically pure gutta percha, which is insoluble in ether and alcohol, and a white and a yellow resin, soluble in boiling alcohol.

Uses. These are numerous and varied. No substance, perhaps, with the exception of caoutchouc, has been ‘tortured’ to so many different purposes. Its perfect plasticity when warm, and its capability of receiving the most delicate impressions, render it invaluable in many cases where india rubber would be useless. Beautiful mouldings, picture frames, and a number of ornamental articles, are made from it. To the chemist and photographer it is of great use as a material for making bottles, carboys, photographic baths, and voltaic battery cells. One of the most important uses to which it has been applied is for enclosing the metallic wires used for telegraphic purposes. Its indestructibility by water, its plasticity, and high insulating power, have rendered it particularly valuable for this purpose. At the International Exhibition of 1862 the Gutta Percha Company exhibited one mile of covered wire perfectly insulated, which was hardly thicker than common sewing cotton. Gutta percha may be rolled into thin transparent sheets, which, being perfectly impervious to moisture, are well adapted for surgical purposes. Again, a solution of gutta percha in chloroform forms an excellent dressing for incised wounds, and a protection for abraded surfaces, burns, &c. It is used in the same way as collodion.

Gutta Percha, Purified. Dr Cattell, of London, has succeeded in purifying gutta percha so perfectly from all extraneous matter, that it presents the appearance of ivory. The raw material is dissolved in a certain solvent, and the solution most carefully filtered until it leaves on evaporation the gutta percha in a pure milk-white condition.

GYP′SUM. This is native sulphate of lime. When baked, to deprive it of water, and ground, it forms plaster of Paris. Gypsum is an excellent manure for certain soils.

HAARBALSAM, Vegetabilischer—Vegetable Hair Balsam (Joh. Andr. Hauschild, Leipsic). A decoction of burdock root, containing a little spirit and coloured green with indigo. (König.) Hager analysed a turbid brownish fluid, which deposited a brown precipitate on standing, and when filtered consisted of a decoction of burdock root with 20 per cent. of spirit.

Haarbalsam Mailandischer—Mailand’s Hairbalsam (Kreller, Nuremberg). Beef marrow, 40 parts; cinchona extract, 5 parts; balsam of Peru, 1 part; storax, 1 part; oil of bergamot, 1 part; oil of lemons, ⁄2 part. (Hager.)

Haarbalsam Ostindischer—East Indian Hairbalsam (Dr Ayer). Contains sugar of lead, sulphur, glycerin, oil of lavender, and water.

Haarbalsam (J. F. Sehwarzlose Söhne, Berlin). A brownish-yellow spirituous aromatic fluid, having nearly the composition of eau de Cologne, with liquid storax, carbonate of potash, and a fat—perhaps derived from cantharides. (Hager.)

Haarbalsam (A. Marquart, Leipsic). A mixture of 83 grammes water perfumed with eau de Cologne, with 12 grammes glycerin, 4·25 grammes milk of sulphur, and 1·2 gramme lead nitrate.

HAD′DOCK. A small sea-fish, allied to the cod, and esteemed an excellent article of food. It is the Gadus æglefinus of Linnæus. Split, smoked, and dried, it is common in the smaller shops of London.

HÆMATEM′ESIS. In pathology, vomiting of blood. See Stomach Affections.

HÆM′ATITE. Syn. Hematite. In mineralogy, one of the most important iron ores. Two kinds are distinguished, the red, which is an anhydrous peroxide of iron, and the brown, which is the hydrated peroxide.

HÆMATOCRYS′TALLIN. A crystalline substance obtained by the action of oxygen and afterwards carbonic acid on the ‘clot’ of blood.

HÆMATOS′IN. Syn. Hæmatin, Red pigment of blood. The red colouring principle of the blood. It is not known in a state of purity. It differs from the other animal principles in containing, as an essential ingredient, the sesquioxide of iron.

HÆMATOX′YLIN. A principle obtained by Chevreul from common logwood (Hæmatoxylon campechianum), and on which its colour appears to depend.

Prep. 1. Infuse logwood chips in water, at a temperature of about 130° Fahr., for 12 hours, filter, and evaporate to dryness in a water bath; digest the residuum in rectified spirit for 24 hours, again filter and evaporate; then add a little water; again gently evaporate and set aside the solution in a cold place that crystals may form; these must be washed in rectified spirit and dried.

2. Digest powdered hard extract of logwood in rectified spirit, and proceed as last.

3. Powdered logwood is mixed with sand and digested for several days in pure ether; the resulting liquid is filtered, evaporated to a syrup, and set aside to crystallise.

Prop., &c. Brilliant reddish-white or straw-yellow crystals, soluble in boiling water, forming an orange-red solution which turns yellow as it cools, but resumes its former colour on being heated. Alkalies in excess change its colour successively into purple, violet, and brown; acids brighten it; with the metallic oxides it forms compounds having a blue, purple, or violet colour.

HÆMOP′TYSIS. In pathology, spitting of blood. It generally arises from extreme fulness of the blood-vessels of the lungs, or the rupture of blood-vessels, as a consequence of ulceration; but sometimes it is induced by excessive exertion or external violence. Depletion, aperients, acidulous and astringent drinks, and nauseants, are the usual remedies. Acetate of lead, in small doses, has been recommended for this affection. When this substance is given, it should be accompanied with a sufficient quantity of free acetic acid, to prevent its being converted into the poisonous carbonate of lead in the system.

HÆM′ORRHAGE. Syn. Hemorrhage; Hæmorrhagia, L. A bleeding or flow of blood. Bleeding may be divided into active, passive, and accidental.—Active hæmorrhage is that arising from a full state of the vessels, or plethora.—Passive hæmorrhage, from general debility of the system, and of the blood-vessels in particular.—Accidental hæmorrhage, from external violence, as blows, wounds, &c. The first generally requires depletion, and the second the usual treatment to establish the general health and vigour of the body. The bleeding from wounds, if extensive, should be arrested by tying the ruptured blood-vessels; or where this cannot be done, and in less important cases, by the application of styptics, as creasote, sulphate of iron, infusion of galls, compound tincture of benzoin, &c.

HAIR. Syn. Capillus, Pilus, L. The hair of the human head has continually formed a subject for the chisel of the sculptor, the pencil of the artist, and the lay of the poet. Nor is this surprising, since all the features of the face, as well as the head it covers, derive from it additional finish and unequalled grace. The hair is, indeed, one of the greatest auxiliaries of personal beauty, and imparts to it some of its principal charms. All nations, in all ages of the world, have been unanimous in their admiration of luxuriant and flowing or gracefully arranged hair.

Of all organic substances, hair is the one least liable to suffer spontaneous change. It is also less affected by aqueous liquids than most other substances. Hence its value in various branches of the useful arts.

The preservation of the hair of the head, independently of its connection with personal beauty, is a matter of the utmost importance in relation to hygiene. In other parts of this work, we have referred to its management under various conditions, but a few observations may be added here.

When the hair is in a weakly state, and either falls off or grows feebly, frequently cutting it will be found of the greatest service. “In the arrangement of the hairs, on the surface of the body, it might be inferred that little existed to excite attention; but this is not the fact, if we are to judge by the careful investigations to which the subject has given rise. The hair-tubes are not placed perpendicularly, but obliquely, in the skin; hence the direction of the hairs, after their escape from the tubes, is in the same sense inclined towards the surface; and the ‘set’ of the hair, from the root to the point, is governed by a law as precise as that which regulates any other of the secondary vital functions. Thus, on the head, the hair radiates from a single point, the crown, to every part of the circumference, making a gentle sweep, behind towards the left and in front to the right. The direction of this sweep is naturally indicated on the heads of children, and is that in which the hair is turned,” (Eras. Wilson.) The same occurs on the face and other parts of the body. In making our toilet, this natural arrangement of the hair should be interfered with as little as possible. Combing it or banding it in an opposite direction to that which it naturally assumes, is highly prejudicial to its healthy growth, and if long persevered in, leads to its premature and rapid decay. The practice now common among ladies, of throwing the hair from the forehead towards the back of the head, is of this reprehensible character.

In addition to our remarks elsewhere, we may here observe, that all the various systems proposed for strengthening or restoring the hair depend for their efficacy upon simple excitation or stimulation of the skin. Friction with the hair-brush, and the use of the ordinary hair-oils, pomades, and washes, are of this kind. The various advertised nostrums for reproducing or restoring the hair are either stimulants or rubefacients of more or less activity, or are emollients, which are directed to be applied by friction, in such a manner as to set up a considerable amount of irritation. When the affection depends on the languid circulation of blood in the part, this treatment often succeeds; but when the hair-bulbs are withered or decayed, or the scalp much attenuated, the restoration of the hair is an impossibility. See Baldness.

HAIR COSMETICS. Under this head are included all preparations which are used for beautifying, preserving, or restoring the hair. These are fully described in different parts of this work, and we shall here merely name the principal heads under which they will be found. The hard pomatums used for keeping the hair, moustache, and whiskers, in form, and sometimes to colour them at the same time, are noticed under Cosmetique; the mucillaginous preparations for stiffening the hair, under Fixature; the compounds for removing superfluous hairs, under Depilatory; the applications for the cure and prevention of baldness, under Pomades and Washes; and those employed to cleanse or beautify the hair under the last two heads, and under Hair Dyes and Oils.

HAIR DYES. Syn. Tinctura cappillorum, L. The practice of dyeing the hair is of great antiquity; and though not so common as formerly, it is still far from infrequent at the present day. The numerous preparations vended for this purpose have generally a basis of lead or silver. Bismuth, pyrogallic acid, and certain astringent vegetable juices, are also occasionally thus employed. The following list embraces all those of any value:

Prep. 1. Litharge, 1 part; fresh-slaked lime and starch, of each 2 parts; all in fine powder, and perfectly dry; mix, and keep the compound in well-corked bottles. This powder is to be made into a thin paste or cream with water (for black), or milk (for brown), and applied to the hair (previously freed from grease with soap and water, and dried), by means of a sponge or brush, or the fingers; observing to rub it well into the roots, and to pass a comb for some time through it, to ensure its coming in contact with every part. The whole must be then covered with a moist leaf of cotton wadding, or some brown paper several times doubled and well damped with hot water, and allowed to remain so for 3 or 4 hours, or even longer; or an oil-silk cap, or a bladder, may be worn, the object being simply to prevent the evaporation of the moisture. After a sufficient time has elapsed, the powder may be removed by rubbing it off with the fingers, and afterwards washing it out with warm soap-and-water. A little pomatum or hair-oil will restore the usual gloss to the hair. Another method of operating is to apply the cream or paste as before, and then to keep rubbing it about the hair with a brush as long as may be required, occasionally adding a few drops of hot water to preserve the whole moist. In this way the action of the dye is facilitated, and the process concluded in a much shorter time.

2. Lime (slaked in the air), 2 parts; carbonate of lead (pure white lead), 1 part; mixed and applied as the last.

3. (Aqua Orientalis.) From grain silver, 2 dr.; steel filings, 4 dr.; nitric acid, 1 oz.; soft water, 1⁄2 fl. oz.; digested together, the solution being afterwards diluted with water, 3⁄2 fl. oz., and filtered. Applied by means of a fine-toothed comb, or a half-worn tooth-brush to the hair, previously well cleaned with soap and water, and dried.

4. (Argentan tincture.) From nitrate of silver, 1 dr.; eau de rose, 1 fl. oz.; nitrate of copper, 2 gr., or q. s. to impart a slight greenish tint. Used as the last.

5. (Dr Cattell.) Nitrate of silver, 11 dr.; nitric acid, 1 dr.; distilled water, 1 pint; sap green, 3 dr.; gum arabic, 1⁄4 dr.; digest together. Used as No. 3.

6. No. 1 Solution. Gallic acid, 7⁄2 gr.; acetic acid, 20 min.; distilled water, 1 fl. oz.

No. 2 Solution. Nitrate of silver, in crystals, 30⁄2 gr.; distilled water, 1 fl. oz.; ammonia sufficient to form the precipitate formed at first.

7. (Chestnut hair dye.) “We have met with the following, but do not guarantee it:— Permanganate of potash gives the hair a beautiful chestnut-brown colour, varying according to the strength of the solution of the salt. A good formula is permanganate of potash, 1 dr.; powdered gum Arabic, 2 dr.; rose water, 3 oz.; mix. Apply carefully with a tooth brush so as to avoid staining the skin. (‘Chemist and Druggist.’)

8. (Hair restorer.) This is in reality a dye. Sulphur, 45 gr.; acetate of lead, 20 gr.; glycerin, ⁄2 oz.; water to make up 10 oz.

9. (Golden hair dye, Aureoline.) A solution of peroxide of hydrogen in water; containing from 3 to 6 per cent. of the peroxide.

10. (Brown hair dye.) Acetate of lead, 2 dr.; hyposulphate of soda, 1 dr.; rose water, 14 oz.; glycerin, 2 oz. Dissolve the acetate of lead and the hyposulphite in separate portions of the rose water; filter separately, mix the solutions, and add the glycerin.

11. (A harmless hair dye. Dr Hager.) Ten parts of subnitrate of bismuth, and 150 parts of glycerin are mixed in a glass vessel and heated in a water bath; solution of potash is then added in small portions, and with continued agitation, until a clear solution has been obtained, to which a concentrated solution of citric acid is added until merely a slight alkaline reaction is observed. Enough orange-flower water is added to make the whole liquid weigh 300 parts; the addition of a small quantity of a solution of an aniline colour completes the preparation.

12. (Chevallier.) Fresh-slaked lime, 5 dr.; water, 1⁄2 oz.; mix, strain through gauze, and pour the milk into a four-ounce bottle. Next dissolve sugar of lead, 5 dr., in water, 3 fl. oz.; add to this solution, dry slaked lime, 1 dr., stir well together, wash the precipitate with a little soft water, drain off the water, then add it to the milk of lime in the bottle, and shake the whole well together, and again before use. Applied as No. 1; but it acts much more quickly.

13. (Delcroix.) From acetate of lead, 2 oz.; prepared chalk, 3 oz.; quicklime, 4 oz.; each in an impalpable powder. Used as No. 1.

14. (Eau d’Afrique—Hopekirk.)—a. Nitrate of silver (cryst.), 1⁄2 dr.; distilled water, 2 fl. oz.; dissolve, and pour the solution into the bottles labelled ‘Solution No. 1,’—b. Liquor of potassa, 3 dr.; sulphydrate of ammonium, 7 dr.; water, 1 fl. oz.; mix, and pour the liquid into the bottles labelled ‘Solution No. 2,’ For use, the hair is moistened by means of a small-toothed comb or tooth-brush, with the Solution No. 1, either alone or diluted with a little water; care being taken to avoid touching the skin, if possible. After the lapse of 8 or 10 minutes the Solution No. 2, diluted with at least 5 times its measure of water, is applied in the same manner, and any spots on the skin removed by rubbing them with the corner of a napkin wetted with the liquid. The skin is then sponged clean with a little warm water, and wiped dry, and the hair is arranged with the comb as usual. It is better to avoid rubbing it or washing it for a few hours. Sometimes the process is reversed, and the liquid No. 2 applied first. In this way the stains on the skin are more readily removed, but the dye is less permanent than when the other plan is adopted.

15. (Eau d’Egypte.) Resembles No. 4 (above).

16. (Essence of Tyre.) Resembles the last.

17. (Grecian water.) Resembles No. 3, or 4.

18. (Dr Hanmann.) Litharge, 275 gr. (say 1 part); quicklime, 1875 gr. (or 6⁄4 parts); hair powder (or starch), 930 gr. (or 3⁄2 parts): all in fine powder. Used as No. 1.

19. (Hewlet’s.) Resembles Spencer’s (No. 28).

20. (Instantaneous.) Moisten the hair first with a solution of nitrate of silver in water (1 to 7 or 8), and then with a weak solution of sulphydrate of ammonium. The colour of the hair, unaltered by the silver solution, instantly turns black when moistened with the sulphuret. See Eau d′Afrique.

21. (La Forest’s.) See Washes.

22. (Orfila’s.) From litharge, 3 parts; quicklime, 2 parts; starch, 1 part. The original form for this article is as follows:—Sulphate of lead, 4 parts; dry fresh-slaked lime, 5 parts; water, 30 parts; boil 1 hour, collect the paste on a piece of calico, and apply it in a similar manner to No. 1.

23. (Pomade dye.)—a. Nitrate of silver, 1 part; nitric acid, 2 parts; iron filings, 2 parts; mix, and let them stand together for 4 or 5 hours, then pour them on oatmeal, 2 parts; next add, lard, 3 parts; and mix well together.

b. From nitrate of silver and cream of tartar, of each 1 dr.; liquor of ammonia, 2 dr.; dissolve, add of lard, 4 dr.; and mix well together.

24. (Poudre d’Italie.) Resembles Orfila’s (No. 22.)

25. (Pyrogallic stain.) A weak solution of crude pyrogallic acid. Another article sold under this name is prepared by distilling nutgalls (coarsely powdered) in a retort, dissolving the solid acid which sublimes in a little hot water, and after mixing this with the acid liquid which also passes over, adding a little rectified spirit. The floating oil is then separated and the solution filtered.

26. (Redwood.) Litharge, 2 oz.; slaked lime and powdered starch, of each 1 oz.; liquor of potassa, 2 dr.; water, q. s. to form a thick cream. Used as No. 1.

27. (Redwood.) Liquor of potassa and distilled water, of each 1 pint; mix, and pass sulphuretted hydrogen through the liquid until it is saturated. Of this solution take 20 oz.; liquor of potassa, 4 oz.; mix, and label it ‘Solution No. 1,’ Next dissolve nitrate of silver, 1 dr., in distilled water, 2 oz.; and label the liquid ‘Solution No. 2,’ Used in the same manner as No. 8 and 20.

28. (Spencer’s.) From sap green, ⁄2 dr.; nitrate of silver, 1 dr.; hot water, 1 oz. Applied as No. 3.

29. (Tincture of walnut.) A strong tincture of the shells of green walnuts, scented with oil of lavender.

30. (Ure.) Litharge, fresh-slaked lime, and bicarbonate of potassa, mixed in various proportions, according to the shade of colour desired. Used like No. 1.

31. (Warren’s.) From litharge, 1 oz.; white lead, 2 oz.; quicklime (in fine powder), 16 oz.; mix, sift through lawn, and at once bottle the mixture. Used like No. 1. Mixed with water, it is said to dye the hair black; with milk, brown.

32. White lead, 1 oz.; fresh slaked lime, 1⁄2 oz.; litharge and oxide of bismuth, of each ⁄2 oz.; water, 1 pint; mix, boil 15 minutes, with frequent agitation, cool, pour it into a bottle, add of solution of ammonia, ⁄4 fl. oz., shake the whole frequently for some hours and the next day pour off the liquid portion from the white sediment which forms the dye. Used like No. 1. It is applied for 8 or 10 minutes for a brown; 30 minutes, or longer, for a black. For the first, it is washed off with water containing a little common soda.

33. The juice of the bark or shell of green walnuts, applied with a sponge. (Paulus Ægineta.)

34. A leaden comb used daily is said to darken the hair, but we have known persons persevere in its use for months without any perceptible change occurring. Premature baldness is a frequent consequence of its use.

Obs. It is right to inform the reader that all those compounds which contain nitrate of silver stain the skin as well as the hair. These stains may be removed, when quite recent, by rubbing them with water containing a little sulphydrate of ammonium (see above) or iodide of potassium in solution; but as this is attended with some trouble and inconvenience, the best way is to avoid the necessity of doing so. The hair-dressers adopt the plan of smearing hard pomatum over the skin immediately surrounding the hair, to protect it from the dye. By very skilful manipulation, and the observance of due precautions, the hair may be thoroughly moistened with the above fluids, without touching the adjacent skin, but this can only be done, in the case of the hair of the head, by a second person. This has led to a preference being given by many to the compounds containing lead, as the colouring matter formed in them does not stain the skin. The hue given by the latter (when pale) is very apt to possess an unnatural redness, but all the shades of colour given by the preparation of silver are rich and unexceptionable. Pyrogallic acid, and the juice of walnuts, also stain the skin, although less intensely and permanently than nitrate of silver.

The detection of dyed hair is often a matter of importance in medico-legal research. The presence of silver may be shown by digesting the hair in a little weak chlorine water or hydrochloric acid, when the resulting chloride of silver may be dissolved out with liquor of ammonia, and submitted to the usual tests. Hair containing lead, when digested in dilute nitric acid, gives a solution of nitrate of lead, in which form it is readily detected. See Lead and Silver.

All the preceding compounds are for dyeing living hair (human); horse-hair, bristles, &c., and other dead hair, may be readily stained by steeping them in any of the ordinary liquid dyes, more especially those employed for wool and silk. See Pomades, Washes, &c.

HAIRWASH, Golden, or Auricomus, is a clear inodorous fluid, which is said to dye hair blond or yellowish red, and really does so. Sold in bottles containing 250 grammes. When exposed to the air the fluid decomposes with time. This hair-dye is an aqueous solution of hydroxyl contaminated with traces of baryta, and can be prepared as follows:—17 parts crystallised caustic baryta and 3 parts potassium chlorate, intimately mixed in fine powder, are melted by a gentle heat. The mass must be washed with cold water to remove the potassium chloride, and the residue shaken in the cold with a solution of 8 parts glacial phosphoric acid in 25 parts water, the whole being cooled with ice. When the peroxide of barium is decomposed, the fluid should be decanted from the precipitate. (Hager.)

HALL MARKS. The ‘Hall Marks’ on articles in gold and silver not only inform us of their fineness, but furnish us with other important particulars.

The Hall Mark (proper) denotes the place of manufacture or assay, being an anchor, for Birmingham; a dagger or 3 wheat sheaves, for Chester; Hibernia, for Dublin; castle and lion for Edinburgh; castle with 2 wings, for Exeter; tree and salmon with a ring in its mouth, for Glasgow; leopard’s head for London; 3 castles, for Newcastle-on-Tyne; a crown, for Sheffield; and five lions’ heads and a cross, for York.

The Duty Mark is the head of the Sovereign, showing that the duty is paid.

The Date Mark is a letter of the alphabet, which varies every year, and with the different companies, thus: the Goldsmith’s Company of London have used from 1716 to 1755, Roman capital letters; from 1756 to 1775, small Roman letters; from 1766 to 1795 old English letters; from 1796 to 1815, Roman capital letters, from A to U, omitting J; from 1816 to 1835, small Roman letters, a to u, omitting j; from 1836, old English letters.

The Standard Mark for gold is, for England, a lion passant; Edinburgh, a thistle; Glasgow, a lion rampant; Ireland, a harp crowned. For silver, a figure of Britannia. If under 22 carats, gold has the figures 18.

The Manufacturer’s Mark is the initials of the maker, as S. H., W. T., C. E., &c.

HAL′OGENS. In chemistry, a name given by Berzelius to chlorine, bromine, iodine, and fluorine. These elements unite with metals to form compounds called ‘haloid salts.’

HAMBURGH POWDER. The material known under this name is used to adulterate chicory. It is composed of roasted and ground peas, coloured with Venetian red.

HAMS. These are usually prepared from the legs of bacon pigs, but those of the sheep are also sometimes used for the same purpose. Smoked ham is strong eating, and rather fit for a relish than for diet, and should be particularly avoided by the dyspeptic and by convalescents.

Choice. A sharp knife thrust under the bone should have a pleasant smell when withdrawn. The recently cut fat should be hard and white, the lean fine-grained, and of a lively red. Those short in the hock are the best.

Curing. An ordinary sized ham requires nearly three weeks, if wet salted, and about a month if dry salted, to cure it perfectly. At the expiration of this time they are ready for smoking. Mutton hams should not lie in pickle longer than 12 or 14 days.

Cooking. Hams should be put into the water cold, and should be gradually heated. A ham of 14 lbs. will take about 4 hours, one of 16 lbs. will take 6⁄2 hours, and one of 20 lbs. about 5⁄2 hours, to dress it properly. “If it is an old ham, it should be soaked for 12 hours previously.” (Soyer.)

Pres. Most grocers and dealers in hams enclose them, after being smoked, in canvas, for the purpose of defending them from the attacks of the little insect, the Dermestes lardarius, which, by laying its eggs in them, soon fills them with its larvæ; or maggots. This troublesome and expensive process may be altogether superseded by the use of pyroligneous acid, applied by means of a painter’s brush.

HANDS. Dirty and coarse hands are no less the marks of slothfulness and low breeding, than clean and delicate hands are those of cleanliness and gentility. To promote the softness and whiteness of the skin, mild emollient soaps, or those abounding in oil, should alone be used, by which means CHAPS AND CHILBLAINS will generally be avoided. The coarse, strong kinds of soap, or those abounding in alkali, should for a like reason be rejected, as they tend to render the skin rough, dry, and brittle. The immersion of the hands in alkaline lyes, or strongly acidulated water, has a like effect. When the hands are very dirty, a little good soft soap may be used with warm water, which will rapidly remove oily and greasy matter. Fruit and ink stains may be taken out by immersing the hands in water slightly acidulated with oxalic acid or a few drops of oil of vitriol, or to which a little pearlash or chloride of lime has been added; observing afterwards to well rinse them in clean water, and not to touch them with soap for some hours, as any alkaline matter will bring back the stains, after their apparent removal by all the above substances, except the last. The use of a little chloride of lime and warm water, or Gowland’s lotion, imparts a delicate whiteness to the skin; but the former should be only occasionally used, and should be well washed off with a little clean water to remove its odour. Glycerine employed in the same manner renders the skin soft, white, and supple. The use of a little sand or powdered pumice stone with the soap will generally remove the roughness of the skin frequently induced by exposure to cold. The hands may be preserved dry, for delicate work, by rubbing a little club moss (LYCOPODIUM), in fine powder, over them. A small quantity of this substance sprinkled over the surface of a basin of water will permit the hand to be plunged to the bottom of the basin without its becoming wet.

HANG′ING. In cases of suspended animation from hanging, the assistance must be prompt and energetic. The body on its discovery should be instantly relieved from the state of suspension and all pressure about the throat. The remedial treatment chiefly consists, in the severer cases, in cupping the temples or opening the jugular vein, and so relieving the head of the blood which is accumulated in its superficial veins in consequence of strangulation. When the body is cold, friction, and the other means used for restoring the animal heat in drowned persons, should be resorted to. See Asphyxia and Drowning.

HARD′NESS. Compactness; solidity; the power of resisting abrasion. Mineral substances are frequently distinguished and identified by their relative hardness. This is ascertained by their power to scratch or be scratched by one another. A valuable table on this subject will be found in the article on Gems.

HAR′MALINE. Syn. Harmalina. An alkaloid, forming yellow-brown crystals, discovered in the seeds of Peganum harmala. It has a bitter astringent and acrid taste, is soluble in alcohol, and forms yellow, soluble salts with the acids. It has been proposed as a yellow dye. By oxidation it yields another compound (harmine), which is a magnificently red dye-stuff, easily prepared and applied. The seeds are produced abundantly in Southern Russia.

HAR′NESS POLISH. See Blacking, &c.

HARTS′HORN. Syn. Cornu cervi, C. Cervinum, Cornu (Ph. L.) L. The “horn of the Cervus elephas” (Ph. L.) or stag.

Hartshorn, Burnt. Syn. Cornu ustum (Ph. L.), Cornu cervi ustum, L. Prep. (Ph. L. 1836.) Burn pieces of harts’ horns until perfectly white, then grind and prepare them in the same way as directed for prepared chalk.

Obs. Finely powdered bone-ash is usually sold for burnt hartshorn, and possesses exactly the same properties.—Dose, 10 to 30 gr., or more 2 or 3 times a day, in rickets, &c

Hartshorn Shavings. Syn. Hartshorn raspings; Rarura cornu cervi, Ramenta c. c., L. Obtained from the turners. Boiled in water, it yields a nutritive jelly. Used by straw-plait workers to stiffen bonnets, &c.

HATCH′ING. See Incubation.

HATS. Those should be chosen possessing a short, smooth, fine nap, and a good black colour; and sufficiently elastic to resist ordinary wear and tear, without breaking or giving way. The HAT BRUSH for daily use should be made of soft hairs, but a stiffer one should be employed occasionally, to lay the nap smooth and close. Grease may be removed by means of porous brown paper, and pressure with a hot iron.

HAY-FEVER. Syn. Hay-asthma, Catarrhus æstivas. Dr Aitken defines this affection as “a variety of asthma or catarrh, occurring generally during the summer months, especially during the inflorescence of the hay crop, or during the drying or conversion of the newly-mown grass into hay, in May and June.” The disease is distinguished by extreme irritation of the eyes, nose, and the whole of the air-passages, these symptoms giving rise in succession to troublesome itching of the eyes and nose, frequent paroxysms of sneezing, with copious discharge from the nostrils, pricking sensation in the throat, cough, tightness of the chest and difficulty of breathing, accompanied sometimes with, and sometimes without, great mucous expectoration. The inhalation of the powder of ipecacuanha sets up similar symptoms with some persons.

Dr Aitken’s definition of hay-fever seems to point to what is pretty generally accepted as its cause, viz. the inhalation of minute and impalpable emanations from certain grasses given off during the period of their flowering and subsequent conversion into hay. This supposition as to the origin of this disease derives support from the circumstance, that it always takes place during the hay season, and at no other; and also that it may be cured by the avoidance of hay-fields and hay-stacks. “Hence going to the sea-coast, and especially to those parts of the coast that are barren of grass, offers a means of protection; and when this cannot be done, such persons obtain refuge in some measure from the cause of irritation, by remaining within doors and shutting out as much as possible the external air during the hay-crop.”

Furthermore, those whom the disease attacks are not particularly subject to catarrh at other times.

Treatment.—Numerous remedies have been proposed and employed for hay-asthma. Dr Elliotson suggests the mild fumigation of the patient’s apartment by means of the solutions of the chlorides of lime or soda; and further advised the sufferers using a smelling bottle containing one or the other of the chlorides. He also employed with success the sulphate of quinine and iron. Mr Gordon recommends the tincture of Lobelia inflata, with the use of the cold shower-bath. Tincture of nux vomica is also said to have been used with good results, as also has Fowler’s solution of arsenic, with very decided advantage, by Dr Mackenzie.

These potent remedies, however, should only be administered under the supervision of a qualified medical practitioner. An esteemed medical friend assures us he has employed the new remedy, Quinetum (the alkaloid of the East India red bark), with the happiest effects. He gives four grains of the quinetum three times a day. The use of an ori-nasal respirator of cotton wool has also been suggested. Great relief has, we know, in a great number of cases, been experienced by snuffing from a smelling bottle containing the following ingredients:— Pure crystallised carbolic acid, 1 dr.; sesquicarbonate of ammonia, 1 oz.; wood charcoal, 1 oz.; oil of lavender, ⁄2 dr.; compound tincture of benzoin, ⁄2 oz.; all reduced to fine powder, and thoroughly mixed.

HEAD′ACHE. Syn. Cephalalgia, L. In pathology, pain in the head. The symptoms of this very general complaint are too well known to require any description. According to pathologists, headache arises either from a sympathy with the stomach and chylopoietic (chyle-forming) viscera, or from a weakness or exhaustion of the power of the encephalon. The former may be called SYMPATHETIC HEADACHE, and the latter NERVOUS HEADACHE. When it attacks only one side of the head it is called HEMICRANIA. The treatment of the first form should consist in restoring the healthy action of the stomach, by the administration of aperients, and by the use of proper food and exercise; or when that viscus is overloaded with undigested food, by the exhibition of an emetic. For this purpose ⁄4 to ⁄2 an oz. of ipecacuanha wine may be taken in a cupful of warm water, which will generally relieve the stomach, especially if its action is assisted by drinking copiously of warm water. Headache is a common accompaniment of indigestion and stomach disease, and in general it will be found that whatever will remove the one will also cure the other. Nervous headaches are relieved by nervous tonics and stimulants, as bark, cascarilla, calumba, and gentian, camphor, ammonia, ether, and wine, the latter in a state of considerable dilution. A cup of strong coffee or strong green tea often acts like a charm in removing this species of headache. Small doses of tincture of henbane have also often a like effect. 20 or 30 drops of laudanum, or, preferably, half that number of liquor opii sedativus, may be taken with advantage as an anodyne, and to induce sleep. Amongst popular remedies may be mentioned ‘nasal stimulants,’ as snuff (cephalic), smelling salts, and aromatic vinegar, the use of which is familiar to every one; and local applications, as very cold water, ether, vinegar, strong spirits, Cologne water, &c., all of which are rubbed over the part of the head affected, with the fingers, or a linen rag dipped in them is laid thereon instead. Pressure on the head has also been used with advantage. Silence, darkness, and repose, are powerful remedies, alike suitable to every variety of headache; and change of air, scene, and occupation, are especially beneficial to those resulting from excessive mental anxiety or exertion. Blisters are extensively applied behind the ears in cases of violent headache.

Headache is often symptomatic of other diseases, especially those of the inflammatory and nervous kind, rheumatism, &c. In all these the primary disease should be sought out and attempted to be cured. In many cases these attacks rapidly yield to a few doses of compound decoction of sarsaparilla containing a little iodide of potassium. Headache in pregnancy may generally be removed by proper attention to the bowels; observing to assist their action, should they require it, by the use of some mild aperient, as castor oil, lenitive electuary, seidlitz powders, &c. When the constitution is very robust, blood may be taken. Headache in bed may frequently be relieved by washing the head with cold water, and discontinuing the use of a nightcap, at the same time preserving the feet warm by wearing worsted socks or stockings.

HEAD′ING. Syn. Beer heading, Cauliflower H. Prep. 1. Alum and green copperas, equal parts, in fine powder.

2. Alum, copperas, and common salt, equal parts.

Used by brewers to make their beer keep its head or froth.

HEALTH. That state of the living body in which all its functions are duly performed. See Hygiene.

HEALTH, GOOD—Gut-Heil (Aust). A liquor containing the extractive matters of calamus root, rhubarb, cinnamon, orange peel, &c., with 35 per cent. of sugar. (Hager.)

HEAR′ING. See Deafness, Ear, &c.

HEART′BURN. Syn. Cardialgia, L. Anxiety and pain about the region of the stomach, generally attended by a sense of gnawing and heat; hence its popular name. Faintness, nausea, and eructation of a thin, acidulous, watery liquid, especially in the morning, are common symptoms of this complaint. The usual causes of heartburn are excess in eating and drinking, the use of improper food, and sedentary habits. A good remedy is a teaspoonful of carbonate of magnesia, or carbonate of soda, in a glass of peppermint or cinnamon water, to which a little powdered ginger may be added with advantage. This dose may be taken 2 or 3 times daily until the disease is removed. Articles of food that easily undergo fermentation should at the same time be avoided, and a dry diet had recourse to as much as possible. Soda water, toast-and-water, and weak spirit-and-water, are the most suitable beverages in this complaint.

HEAT. Syn. Caloric; Caloricum, L. The consideration of this subject belongs to physics and chemistry. Much useful information, in connection with it, will, however, be found in this work under the heads Ebullition, Evaporation, Expansion, Refrigeration, &c.

HEAVY SPAR. Native sulphate of barium. See Baryta.

HED′ERIN. Syn. Hederina, L. From the decoction of the ground seeds of ivy (Hedera helix), boiled in water, along with a little slaked lime or magnesia, the precipitate being afterwards digested in rectified spirit, and the filtered tincture evaporated. Febrifuge and sudorific.

HEIGHT, Average of Man. The ‘Boston Journal of Chemistry’ gives the following particulars of the average height of man:—“The Yankee would appear to be the tallest of civilised men, if we may trust some statistics given in foreign journals as the result of the measurement of over half a million men. The mean height of the American Indian is 67·934 inches; of the American white man, 67·672; Scotch, 67·066; English, 66·575; Russian, 66·393; French, 66·277; Mexican, 66·110.” If the Yankee carries off the palm as the tallest of men, he also does so for his tallest tales; but if weight were introduced into the calculation, we think our Transatlantic cousins would rank last.

HEIGHTS. The following table, calculated by Regnault, gives the temperature at which water boils at the corresponding heights of the barometric column. The figures have been confirmed by direct observation.

Boiling Points of Water at different Pressures.

Boiling Point. Deg. Fahr. Barometer. Inches. Boiling Point. Deg. Fahr. Barometer. Inches. Boiling Point. Deg. Fahr. Barometer. Inches.

184 16·676 195 21·124 206 26·529

185 17·047 196 21·576 207 27·068

186 17·421 197 22·030 208 27·614

187 17·803 198 22·498 209 28·183

188 18·196 199 22·965 210 28·744

189 18·593 200 23·454 211 29·331

190 19·992 201 23·937 212 29·922

191 19·407 202 24·441 213 30·516

192 19·822 203 25·014 214 31·120

193 20·254 204 25·468 215 31·730

194 20·687 205 25·992 216 32·350

HEL′ENIN. See Inulin.

HELIOG′RAPHY. See Photography.

HEL′LEBORE. Syn. Black hellebore; Helleborus (Ph. L.), L. “The rhizome and root” of “Helleborus niger” (Ph. L.) or black hellebore. It is alterative and emmenagogue, in small doses (2 to 8 gr.); and a drastic hydragogue purgative and anthelmintic in larger ones (10 to 20 gr.) See White Hellebore.

HELLEBOR′IE. Syn. Soft resin of hellebore. An odourless, acrid substance, extracted by alcohol from black hellebore, and on which, according to Vauquelin, the activity of that drug depends.

HEM′LOCK. Syn. Conii Folia (B. P.); Conium (Ph. L. E. & D.), L. In pharmacy, “the fresh and dried leaf of the wild herb Conium maculatum,” or spotted hemlock. The first is used to make the extract; the last, the tincture and powder.

Hemlock is a powerful narcotic acrid poison, occasioning stupor, delirium, paralysis, convulsions, coma, and death. In small doses it is anodyne, alterative, resolvent, antispasmodic, and anaphrodisiac, and has been exhibited in cancer, dropsy, epilepsy, rheumatism, scrofula, syphilis, and other diseases.—Dose, 3 or 4 gr. of the powder, twice or thrice daily, until some obvious effect is produced.

Hemlock, whether in leaf (conii folia) or powder (pulvis conii) rapidly deteriorates by keeping. When good, the powder, triturated with solution of potassa, exhales a powerful odour of conia.

In cases of poisoning by hemlock, the treatment is similar to that noticed under Aconite. See Conia, Extract, Tincture, &c.

HEMP. Syn. Cannabis, L. In botany the typical genus of the natural order Cannabinaceæ. The common hemp, from the fibres of which cordage is made, is the species Cannabis sativa. The fruit of this plant (hemp seed) is demulcent and oleaginous. It is said that the plumage of bullfinches and goldfinches fed on it for too long a time, or in too large a quantity, changes from red and yellow to black.

Hemp, Indian. Syn. Hashish, Cannabis Indica. This plant, now so largely used in medicine, is a variety of Cannabis sativa, or, perhaps, the same simply rendered more active by climate. The parts employed in Asia for the purposes of intoxication, and in Europe as medicine, are the herb or leaves and the resin. The ‘gunjah’ sold in the bazaars in the East Indies is the plant, just after flowering, dried, and pressed together. ‘Bang,’ ‘bhang,’ ‘subjee,’ or ‘sidhee,’ consists of the larger leaves and capsules without the stalk. The concrete resinous exudation from the leaves, stems, and flowers, is called ‘churrus,’ and in this country ‘resin of Indian hemp.’ ‘Hashish’ seems to be a general term for the preparation of hemp.

Dr Preobraschensky, has lately subjected hashish to a chemical analysis, and states that he has found an alkaloidal body, not only in the commercial substance, but also in the flower-tops of the hemp itself, and the pure extract prepared from it, which was recognised as nicotine.

Indian hemp is anæsthetic, anodyne, exhilarant, antispasmodic, hypnotic, and narcotic. In the East it is commonly used as an intoxicant, either by smoking it, like tobacco, or swallowing it. The inebriation produced by it is of an agreeable or cheerful character exciting the party under its influence to laugh, dance, sing, and to commit various extravagancies. It also acts as an aphrodisiac, augments the appetite for food, and, in some cases, occasions a kind of reverie and catalepsy. In this country its action is less marked. It has here been chiefly administered under the form of alcoholic or resinous extract. See Extract of Indian Hemp.

HEN′BANE. Syn. Hyoscyami Folia (B. P.); Hyoscyamus (Ph. L. E. and D.), L. In pharmacy, “the fresh and dried stalk-leaf of the biennial herb, Hyoscyamus niger” (Ph. L.), or common biennial or black henbane. The first is used for preparing the extract; the last, for the powder and tincture.

Henbane is anodyne, hypnotic, antispasmodic, and sedative. It differs from opium in not being stimulant, and by not confining the bowels; and hence may be administered in cases in which that drug would be improper. In large doses it acts as a powerful narcotic poison, producing obscurity of vision, dilatation of the pupils, delirium, phantasms, coma, &c.—Dose, 3 to 10 gr., in powder. It is usually given in the form of extract or tincture. The antidotes, &c., are the same as those noticed under Opium.

HEN-COOPS, Fumigator for. Consisted wholly of coal-tar.

HE′PAR. Syn. Liver. A name given by the older chemists to various combinations of sulphur, from their brownish or liver colour; as ‘hepar antimonii,’ ‘hepar sulphuris,’ &c. See Antimony (Liver of), Potassium (Sulphide), &c.

HERBAR′IUM. [Eng., L.] Syn. Hortus siccus, L. A collection of dried specimens of plants; hence called HORTUS SICCUS, or dry garden. Plants for the herbarium should be gathered on a dry day, and carried home in a tin-box (‘VASCULUM’), or other convenient receptacle which will preserve them fresh for a time. Those which have collected moisture in their leaves should be allowed to dry, their stalks being placed in water to keep them alive. Plants with very thick, succulent leaves or stems must be killed by immersion in hot water before they can be safely placed in the drying press. The press consists simply of a few stout boards with a screw—or, still better, a number of heavy weights, bricks, or stones—for pressing them together. The specimens of plants, when all superficial moisture has been removed, are placed between layers of bibulous paper (BOTANICAL PAPER), care being taken that the parts of each are arranged in a natural manner. The sheets containing the specimens are then placed between the boards, and pressure is applied. This must be very gentle at first, and should be gradually increased as the plants become dry. The paper is changed every day or every second day, and the damp sheets are dried for use at a future time. When properly dried, the specimens are placed on sheets of writing paper, and fixed by a few stitches of thread, a little gum, or strips of gummed paper. The name of the genus and species, and the locality where found, &c., are then marked beside each. Camphor or a little corrosive sublimate may be used to preserve herbaria from the ravages of insects. The preparation of an herbarium offers an almost endless source of amusement to the ingenious, whilst the specimens so collected, if well preserved, are almost as useful to the botanist as the living plants.

HERBS. Syn. Herbæ, L. The collection and drying of herbs for medicinal purposes and perfumery are noticed under Vegetable Substances.

Amongst cooks, several aromatic herbs, either fresh or dried, are used for seasoning. “In many receipts is mentioned a bunch of sweet herbs, which consists, for some stews and soups, of a small bunch of parsley, two sprigs of thyme, and one bayleaf; if no parsley, then of four sprigs of winter savory, six of thyme, and one bayleaf.” (Soyer.)

HER′NIA. See Rupture.

HER′RING. A well-known small sea-fish, belonging to the family of Clupeidæ, a branch of the order Malacopterygii. As an article of food, herrings are of a vast importance to a large proportion of the population of Europe. When recently caught and dressed by broiling or boiling, they are wholesome and agreeable; but if fried, or long kept, they become strong and oily, and are then apt to offend the stomach. The preparation of salted and dried of smoked herrings (bloaters, red herrings) furnishes employment for thousands, both in these countries and Holland. Real Yarmouth bloaters and Dutch herrings are highly esteemed by many as a relish. Salted herrings are said to be diuretic. The pickle was formerly used in clysters, dropsies, &c. M. Soyer calls this fish “the poor man’s friend,” and tells us that, after being “cleaned and scaled, and the head removed,” it should be “opened in the back, and the gut taken out.” Also that “the way to ascertain if a herring is too salt is to take the fish in the left hand, and pull out a few of the fins from the back, and to taste them. You may thus find out the quality and flavour. This plan is adopted by the large dealers.”

HESPER′IDIN. A peculiar substance obtained from the white portion of the rind of oranges, lemons, &c. It forms crystalline silky needles, is odourless, tasteless, fusible, soluble in alcohol and ether, less soluble in water. Hesperidin is a glucoside.

HIC′COUGH (hĭk′-ŭp). Syn. Hiccup; Singultus, L. A convulsive motion of the diaphragm and parts adjacent. The common causes are flatulency, indigestion, acidity, and worms. It may generally be removed by the exhibition of warm carminatives, cordials, cold water, weak spirits, camphor julep, or spirits of sal-volatile. A sudden fright or surprise will often produce the like effect. An instance is recorded of a delicate young lady that was troubled with hiccough for some months, and who was reduced to a state of extreme debility from the loss of sleep occasioned by it, that was cured by a fright, after medicines and topical applications had failed. A pinch of snuff, a glass of iced soda water, or an ice-cream, will also frequently remove this affection.

HI′ERA-PI′CRA. See Powder of Aloes and Canella.

HIP′POCRAS. An aromatic medicated wine, formerly much used in England, and still employed on the Continent.

Prep. Lisbon and Canary wine, of each 12 pints; cinnamon, 2 oz.; white canella, ⁄2 oz.; cloves, mace, nutmeg, ginger, and galangal, or cardamoms, of each 1 dr.; bruise the spices, and digest them in the wine for three or four days; strain, and add of lump sugar, 2⁄2 lbs.

HIPPU′RIC ACID. HC9H8NO3. Syn. Acidum hippuricum, L. A compound discovered by Liebig in the urine of the horse, cow, and other graminivora, in which it exists as hippurate of potassium or sodium.

Prep. Concentrate fresh cow’s urine by a gentle heat to about ⁄10th its bulk, filter from deposit, mix the liquid with excess of hydrochloric acid, and set it aside to crystallise. It may be decoloured by redissolving it in boiling water, and treating it with animal charcoal, or with a little chloride of lime along with some hydrochloric acid, and re-crystallising it.

Obs. Hippuric acid, when pure, forms long, slender, milk-white, square prisms; it is soluble in 400 parts of cold water; it also dissolves in hot alcohol. When strongly heated, it yields benzoic acid, benzoate of ammonia, and benzonitrile, with a coaly residue. The urine of horses or cows, left to itself for some time, or evaporated at a boiling temperature, yields not a trace of hippuric acid, but only benzoic acid. Nitric acid and hot oil of vitriol convert it into benzoic acid. Boiling hydrochloric acid converts it into benzoic acid and glycocoll. With the bases it forms salts, which are called hippurates. See Benzoic Acid.

HIPS. Syn. Heps; Rosa canina (Ph. L.). The fresh fruit of the dog rose (Rosa canina), or wild briar. Used to make a conserve.

HOL′LANDS. Syn. Geneva, Schiedam, Hollands gin, Dutch g. Prep. 1. The materials employed in the distilleries of Schiedam, in the preparation of this excellent spirit, are 2 parts of the best unmalted rye and 1 part of malted bigg, reduced to the state of coarse meal by grinding. About a barrel (36 galls.) of water, at a temperature of from 162° to 168° Fahr., is put into the mash-tun for every 1⁄2 cwt. of meal, after which the malt is introduced and stirred, and, lastly, the rye is added. Powerful agitation is next given to the magma till it becomes quite uniform, when the mash-tun is covered over with canvas, and left in this state for two hours. Agitation is then again had recourse to, and the transparent ‘spent wash’ of a preceding mashing is added, followed by as much cold water as will reduce the temperature of the whole to about 85° Fahr. The gravity of the wort at this point varies from 33 to 38 lbs. A quantity of the best pressed Flanders yeast, equal to 1 lb. for every 100 galls. of the mashed materials, is next stirred in, and the whole is fermented in the mash-tun for about 3 days, or until the attenuation is from 7 to 4 lbs. (sp. gr. 1·007 to 1·004). During this time the yeast is occasionally skimmed off the fermenting wort. The wash, with the grains, is then transferred to the still, and converted into ‘low wines.’ To every 100 galls. of this liquor, 2 lbs. of juniper berries (3 to 5 years old), and about 1 lb. of salt, are added, and the whole is put into the low-wine still, and the fine spirit drawn off by a gentle heat, one receiver only being employed. The product per quarter varies from 18 to 21 galls. of spirit, 2 to 3 o. p.

2. (Best Hollands.) Hollands rectified to the strength of 24° Baumé (sp. gr. ·9125, or about 6 o. p.).

3. (English-made.)—a. From juniper berries (at least a year old, and crushed in the hands), 3 lbs.; rectified spirit, 1⁄2 gall. (or proof spirit, 2⁄2 galls.); digest, with agitation, for a week, and then express the liquor; after 24 hours’ repose, decant the clear portion, add it to good corn spirit, at 2 or 3% overproof, 90 or 100 galls., and mix them well together.

b. From juniper berries, 2⁄2 lbs.; sweet fennel seed, 5 oz.; caraway seed, 3⁄2 oz.; proof spirit, 2 galls.; corn spirit, 90 or 100 galls.

c. As the last, with the addition of Strasburg turpentine or Canadian balsam, 1 lb.

d. To either of the last two or three add a very small quantity of ground cardamoms or horse-radish. Some compounders also add 4 or 5 cloves of garlic, or about 15 gr. of assafœtida, with 1 gr. of ambergris rubbed to a powder with a little white sand or lump sugar. Good plain gin may be advantageously employed in lieu of the corn spirit ordered above, when expense is no object.

Obs. The last four forms, which are only given as examples, produce a very pleasant spirit, if it is kept for some time to ‘mellow.’ Age is one of the principal causes of the ‘creaminess’ of foreign gin, which usually lies in bond for some time before being consumed. The product is, however, much superior if the ingredients are rectified along with 20 galls. of water, and about 14 lbs. of salt, by a gentle heat.

It will be seen from the above that the superior flavour of Hollands spirit depends more on the peculiar mode of its manufacture than on the quantity of juniper berries employed; 2 lbs. of them, when new, being barely equivalent to 1 oz. of the essential oil; and when old, to less than ⁄2 oz., a quantity wholly insufficient to flavour 100 gallons of spirit. The Dutch distillers, most noted for this liquor, add a little pure Strasburg turpentine and a handful or two of hops to the spirit, along with the juniper berries, before rectification. The former substance has a pale yellowish-brown colour, and a very fragrant and agreeable smell, and tends materially to impart that fine aroma for which the best geneva is distinguished. At Rotterdam sweet fennel seed is commonly added as a flavouring; and at Weesoppe Strasburg turpentine and fennel seeds, or the essential oil of fennel, are frequently substituted for a large portion of the juniper berries.

Schiedam Hollands is considered the best; the next quality is that of Rotterdam; after these comes that of Weesoppe.

Attempts have been made by Mr Robert Moore, and others to introduce into general consumption in this country a home-made liquor, resembling and prepared in the same manner as foreign geneva, “but the palates of our gin-drinkers were too corrupted to relish so pure a spirit.”

HOMŒOP′ATHY. Syn. Homœopathia, L. A medical hypothesis promulgated at the commencement of the present century by the late Dr Hahnemann, of Leipsic, according to which diseases may be cured by the administration of minute doses of medicines capable of producing in healthy persons affections similar to those it is intended to remove. The doctrine that “similia similibus curantur” had long previously been practically acted on, to a limited extent, in certain cases, in legitimate medicine (allopathy, heteropathy), although not verbally recognised as belonging to its system. The administration of infinitesimal doses is an absurdity which homœopathy, however, alone can claim. According to this method, the millionth of a grain is often an excessive dose; whilst billionths and decillionths, quantities so small as to be vastly beyond human perception, form the common doses. This reduces the whole practice of homœopathy to a system of doing nothing beyond regulating the diet and habits of the patient. “All judicious practitioners have long been agreed that there are many cases which are best treated in the manner just mentioned, and in which physic does more harm than good; in which, in short, a sensible physician endeavours to amuse the patient, whilst nature cures the disorder; so that the frequent success of homœopathic treatment may be explained, without admitting the principle upon which it is presumed to be founded.” (Brande.)

HON′EY. Syn. Mel (B. P.), L. The sweet substance elaborated by the domestic bee from the juices of the nectaries of flowers, and deposited in the cells of wax forming the honeycomb.

Var. Pure honey consists of a syrup of uncrystallisable sugar and crystalline saccharine grains, resembling grape sugar.—‘Virgin honey’ is that which flows spontaneously from the comb.—‘Ordinary honey,’ that obtained by heat and pressure. The former is pale and fragrant; the latter darker, and possessing a less agreeable taste and smell.—‘English honey’ is chiefly collected from furze and broom flowers, and is more waxy than that from the South of Europe;—‘Narbonne honey,’ chiefly from rosemary, and other labiate flowers, very fine;—‘Poisonous honey’ is found near Trebizond, in Asia, its toxic effects being due to the bees having collected it from a poisonous plant, the Azalea pontica.

Pur. Honey is frequently adulterated with treacle, potato-sugar syrup, potato farina, starch, and wheat flour. The first may be detected by the colour and odour; the second in the way noticed under Sugar; and the others by the honey not forming a nearly clear solution with cold water, and striking a blue colour with iodine. When it contains wheat flour, and is heated, it at first liquefies, but on cooling it becomes solid and tough. The absence of starchy matter or flour is easily proved by the following test:—Boiled with water for five minutes, and allowed to cool, it should not become blue with iodine water—indicating absence of flour.

Uses, &c. Honey is nutritive and laxative, but rather apt to gripe. It is employed in the preparation of OXYMELS and GARGLES, and also to cover the taste of nauseous medicines, which it does better than sugar. Clarified honey is alone ordered to be used in medicine.

Honey, Clarified. Syn. Refined honey, Strained h.; Mel depuratum (Ph. D.), Mel præparatum, L. The honey is simply melted by the heat of a water bath, and strained whilst hot through flannel (Ph. D.); or—it is melted as last, and the scum removed (Ph. U. S.); or—it is melted with 1-3rd its weight of water, skimmed, strained through flannel, and evaporated until it reaches the sp. gr. 1·261. (P. Cod.) Honey is not to be employed without being desquamated. (Ph. L.)

Obs. Clarified honey is less agreeable than raw honey, and has lost the crystalline character of the latter; but it is less liable to ferment and gripe. The use of copper and iron vessels or implements should be avoided, as honey acquires a dark colour by contact with them. Berlin-ware, stone-ware, or well-silvered or tin copper pans, should alone be used. On the large scale, one or other of the following plans are adopted:—

1. The honey is mixed with an equal weight of water and allowed to boil up 5 or 6 times without skimming; it is then removed from the fire, and after being cooled, brought on several strong linen strainers, stretched horizontally, and covered with a layer of clean and well-washed sand, an inch in depth; the sand is rinsed with a little cold water, and the mixed liquor is finally evaporated to the thickness of syrup.

2. Dissolve the honey in water, as last, clarify with white of egg, and evaporate to a proper consistence.

3. Dissolve in water, add 1⁄2 lb. of animal charcoal to every ⁄4 cwt. of honey, gently simmer for 15 minutes, add a little chalk to saturate excess of acid, if required, strain or clarify, and evaporate.

4. Honey, 1 cwt.; water, 9 galls.; fresh burnt animal charcoal, 7 lbs.; simmer for 15 minutes, add a little chalk to saturate free acid (if required), strain or clarify, and evaporate as before.

HONEYS. (In pharmacy.) Syn. Melita, L. These are minor preparations, now almost superseded by ‘syrups’ (Syrupi). The mellita of the Ph. L., including two ‘oxymels,’ are only four in number.

Honey of Bo′′rax. Syn. Mel boracis (B. P. Ph., L. E. & D.), L. Prep. (B. P.) Finely powdered borax, 1; clarified honey, 7; mix. Astringent, detersive, and cooling. It is employed in aphthæ of the mouth, excessive salivation, &c. A great improvement would be to dissolve 1 of borax in 1 of glycerin, and then add 6 of honey.

Honey of Col′chicum. Syn. Mel colchici, L. Prep. (Beasley.) Dried colchicum 1 part; water (at 140°), 16 parts; infuse for 12 hours, strain, let it settle, and boil the clear liquor with white honey, 12 parts, to the consistence of a syrup. See Colchicum.

Honey of Liq′uorice. Syn. Mel glycyrrhizatum, L. Prep. (Ph. Hamb.) Honey and a strong infusion of liquorice boiled to a proper consistence. Emollient, pectoral, and laxative.

Honey of Male Fern. Syn. Mel filicis, L. Prep. (Dunglison.) Ethereal extract of male fern, 30 gr.; honey of roses, 4 dr.; mix. In tapeworm.—Dose. One half at bedtime, followed by the remainder in the morning.

Honey of Mercury. Syn. Mel hydrargyri, L. Prep. (Bell.) Mercury, 1 dr.; honey, 1 oz.; triturate till the globules disappear. Allard adds of oil of cloves, ⁄2 dr. Properties similar to those of mercurial pill. It is chiefly used as an application to ulcers of the throat.

Honey of Ro′′ses. Syn. Mel rosæ (Ph. L. and E.), L. Prep. 1. (Ph. L.) Dried petals of the red rose (the leaves separated), 4 oz.; boiling water, 16 fl. oz.; macerate for 2 hours; lightly press them in the hand, and strain; then add 8 fl. oz. more of boiling water to the roses, macerate for a short time, and again gently express the liquor; to this add the other half; next add to the mixed liquors, honey, 5 lbs.; and evaporate in a water bath, so that, the infusion which was set aside being added, it may become of a proper consistence.

2. (Ph. E.) Dried rose petals, 4 oz.; boiling water, 2⁄2 pints; infuse for 6 hours, and gently squeeze out the liquor; after the impurities have subsided, decant the clear, add of honey, 5 lbs., and evaporate as before, to a proper consistence, removing the scum which forms. Used to make astringent gargles. It must not be boiled in a copper or iron vessel, as they will spoil the colour. The last form is that commonly adopted in trade.

Honey of Squills. Syn. Mel scillæ, L. Prep. 1. Thick clarified honey, 3 lbs.; tincture of squills, 2 lbs.; mix.

2. (Soubeiran.) Dried squills, 1 oz.; boiling water, ⁄4 pint; infuse 2 hours, strain, add of honey, 12 oz.; and evaporate to a proper consistence. Resembles OXYMEL OF SQUILLS (nearly).

Honey of Verdigris. Egyptiacum.

Honey of Vi′olets. Syn. Mel violæ; L. Prep. From clarified honey, 2 parts; expressed and depurated juice of violets, 1 part. Resembles syrup of violets.

HON′EY DEW. Syn. Ros mellitus, L. A sweetish matter ejected upon the leaves of plants by certain aphides.

HOOP′ING COUGH. See Whooping Cough.

HOPS. Syn. Lupulus (B. P.), L. “The catkins of the female plant of the Humulus lupulus” or common hop. (B. P.) “The dried strobiles.” (Ph. D.) The hops of commerce are the strobiles or catkins (LUPULI STROBILI, L. AMENTA) of the hop plant. The yellow powder or small lupulinic grains or glands (LUPULIN), which are attached to the strobiles, are the portion on which their characteristic qualities chiefly depend.

The hop is tonic, stomachic, and moderately narcotic. It is used in diseases of local debility with morbid vigilance and other nervous derangement, producing sleep where opiates are objectionable. Hops may be used topically as a fomentation or a poultice, as a resolvent or discutient in painful swellings and tumours. The golden dust attached to the scale of the hop is sometimes administered in doses of from 5 to 10 grains. Very freshly dried hops, made into a pillow, procure sleep.

In the choice of hops, care should be taken to select those that have large cones or strobiles, that are the most powerfully odorous and most free from leaves, stems, scaly fragments, and sticks, and which, when rubbed between the hands, impart, in the greatest degree, a yellowish tint and glutinous feeling to the skin. The tightness with which they are packed should also be noticed; as, without being very firmly pressed together, and quite solid they soon spoil by keeping. The finest flavoured hops are the ‘GOLDINGS,’ grown chiefly in middle and east Kent; the ‘WHITEBINES’ of Farnham and Canterbury; and the Worcester hops, grown on the red soils of the vale of the Severn. These are principally employed for the finer class of ales. Mid Kent and Sussex hops are also used for ale, but have an inferior colour and flavour. The best hops are packed in sacks of fine canvas, termed ‘pockets,’ weighing from 1⁄4 cwt. to 1⁄4 cwt. each; and the inferior qualities in coarse ‘bags,’ of about double the size. The former are mostly purchased by the ale brewers, and the latter by the porter brewers. When hops are older than of last season’s growth they are termed ‘yearlings,’—when of the second season’s growth, ‘old,’—and when three years, or older, ‘old olds.’ See Brewing, Extract, Humulin, Lupulin, Tincture, &c.

HOOSE. Young cattle, especially calves, as well as sheep and lambs, are frequently liable to attacks of a species of bronchitis, caused by the presence in the bronchial tubes of minute worms. They are mostly so attacked in autumn.

Treatment. For a calf of six months old give half an ounce of oil of turpentine in two ounces of linseed oil, to be repeated once or twice after an interval of two days. Half this dose may be given to sheep. The mixture should be administered by the mouth, and not by the nostrils, as usually recommended. Calves should additionally be comfortably housed at night, and be fed with a little oil cake and other good food.

HORE′HOUND. Syn. White horehound; Marrubium vulgare (Linn.), L. This herb has long been a popular remedy in chronic pulmonary complaints, especially catarrh, and in uterine and liver affections. Horehound tea (THEA MARUBII, INFUSUM MARUBII) is prepared by infusing 1 oz. of the herb in boiling water, 1 pint, for an hour;—syrup of horehound (SYRUPUS MARUBII), by thickening the infusion of tea with sugar;—candied horehound (MARUBIUM CONDITUM), by mixing 1 pint of horehound juice with 8 or 10 lbs. of white sugar, boiling the mixture to a candy height, and pouring it, whilst warm, into moulds, or small paper cases, well dusted with finely powdered lump-sugar; or by pouring it out on a dusted slab, and cutting it into squares. See Candying.

HORN. For the purposes of the turner and comb-maker, horns of the goat and sheep are preferred on account of their superior whiteness and transparency. For medical purposes, those of the stag (HARTSHORN) are ordered to be employed.

Horn is dyed with the same dyes, and in a similar manner to bones and ivory.

Horn is softened, bent, and moulded, by means of heat and pressure. For these purposes boiling water and a screw press are commonly employed.

Horn is reduced to plates or sheets by sawing it, and then exposing it to powerful pressure between hot iron plates; the pith having been previously removed, and its texture softened by soaking for some days in water, and subsequent boiling in that liquid.

Surfaces and edges may be united or cemented together by softening the horn by the heat of boiling water, placing the parts in contact under strong pressure, and exposing the whole thus arranged to the heat of boiling water.

Horn is stained or party-coloured to imitate tortoise-shell, by a solution of terchloride of gold, for the red portion; nitrate of silver, for the dark brown and black; and nitrate of mercury (hot), or a paste made of red lead, and potash or quicklime, for the brown. When the last is used the horn must be heated and exposed to its action for some hours.

Horn Silver. (Ag. Cl.) A native chloride of silver, which occurs either crystallized in cubes, or as a compact semi-transparent mass.

HORS-D’ŒUVRES. [Fr.] Syn. Assiettes, Fr. Small entrées, as ‘aiguillettes,’ ‘ragouts,’ plates of sardines, anchovies, or other relishes, served at dinner between the leading dishes. ‘Assiettes volantes’ (flying plates) are dishes handed round to the guests, but not placed on the table.

HORSE. Syn. Equus, L. This most useful quadruped belongs to the family Equidæ, distinguished by a single digit and hoof on each foot. The horse can scarcely be said to exist at the present day in its natural wild state, as the so-called ‘wild-horses’ of America and Asia are but the progeny of horses which have escaped from the haunts of civilisation. Of all animals the horse is most useful to man. Independently of its value as a beast of burden and draught, its skin, its hide, intestines, and bones, furnish us with leather, the thongs of whips, gut, grease, bone-black, manure, &c. The excrement, fat, and hoof were included in the Materia Medica of the Ph. L. 1618. The flesh is eaten in some countries, and was formerly esteemed to possess many virtues.

Injuries of a serious character, and even death, are often occasioned by horses running away, or becoming unmanageable. Various methods have been proposed to prevent accidents of this kind, and to place the animal entirely under the power of its rider or driver. In Russia, around the horse’s neck, near the neck strap, is placed a cord with a running knot. To this slip-noose is attached a pair of reins, which always lie thrown over the dashboards, ready to be seized at once. When the horse starts, and becomes unruly, the gentleman takes up this cord, and tightens the horse’s throat, so that he cannot take breath. The most furious horse stops instantly, and will not fall or kick. See Bedding, Bran Mash, Broken Knees, Broken Wind, Clipping, Canker, Catarrh, Choking, Chorea, Cholic, Constipation, Corns, Crib-biting, Curb.

HORSE BALLS. See Veterinary Medicine.

HORSES, Condition Powder for. The principal ingredients were: Fenugreek, liquorice root, resin, brimstone, common salt, nitrate of potash, and a green powder, probably senna. It contained traces of calcium and magnesium carbonates; alumina, silica, and iron.

HORSE POW′ER. This term was first employed by James Watt to express a power capable of raising 33,000 lbs. one foot high per minute. The effective pressure on the surface of the piston was estimated at 7 lbs. to the square inch, and hence the area of the piston, in square inches, multiplied by 7, gave the gross effective moving pressure, and the space passed over by this piston in a minute gave the distance through which the pressure was exerted, or the weight was raised. From these data the horse power was easily calculated. In process of time improvements in the formation of boilers and steam engines increased the effective pressure on the piston, and, consequently, the power of the engine. In modern engines the actual power is commonly from 2 to 4 times greater than the nominal power, which is, however, still retained as the unit of power in commercial calculations.

HORSERAD′ISH. Syn. Armoracia radix. (B. P.). “The fresh root of Cochlearia Armoracia” (B. P.). Horseradish is pungent, acrid, stimulant, and rubefacient. It is also regarded as diaphoretic, diuretic, and antiscorbutic. It forms a useful masticatory in hoarseness, sore throat, and toothache. As a condiment, it provokes the appetite and assists digestion. Reduced to shreds (scraped horseradish), it forms a common and excellent accompaniment to roast beef. The root of aconite or wolfsbane, which somewhat resembles it in appearance, has occasionally been mistaken for it, with fatal results; the two are, however, readily distinguished from each other, as the taste of horseradish is warm and pungent, approaching that of mustard, whilst aconite is bitter, and its odour is earthy and disagreeable, and after a few minutes’ contact with the lips, tongue, and fauces, produces a sensation of numbness, and tingling. See Aconitum Napellus; under which article will be found engravings of the two roots. The root may be kept fresh for some time if buried in sand in a cool place. Horseradish powder is prepared from the roots gathered in November or December, and dried by a gentle heat or exposure to a current of dry air. It is used as a condiment.

HOR′TICULTURE. Syn. Gardening. The art of cultivating gardens. According to Loudon, horticulture differs from agriculture, chiefly in the comparatively limited space over which it extends, and in being conducted by manual labour; whilst the latter is performed jointly by human and animal labour, in fields, or on an extensive tract of land called a farm.

HOR′TUS-SICCUS. See Herbarium.

HOS′PITAL GAN′GRENE. Syn. Phagedæna gangrenosa. L. A species of ulcerating mortification, particularly characterised by its infectious nature, and its tendency to attack wounds and ulcers in crowded hospitals, so that often the most trifling operation cannot be performed with safety. Under its influence the parts are rapidly destroyed, not by the formation of ordinary sloughs, as in common mortification, but by their conversion into an ash-coloured viscid substance interspersed with bloody specks. The treatment is similar to that noticed under Mortification, but here, above all things, thorough ventilation must be established, and persevered in, and, when possible, change of situation sought.

HUILE. [Fr.] Oil; a term applied to various substances and preparations on account of their smoothness, consistence, or real or imaginary emollient or oleaginous nature. See Liqueur, Oil, &c.

Huile Acoustique. Prep. From garlic and bay leaves, of each, ⁄2 oz.; olive oil, ⁄2 lb.; boiled together for 15 minutes, and strained. Used in ear-ache and deafness. A little is dropped on cotton wool and placed in the ear.

Huile, Antique. See Oils (Hair).

Huile Liqueureuse. Prep. 1. (De la Rose.) From eau de rose, 1 part; simple syrup, 2 parts; mixed together.

2. (Des fleurs d’oranges.) From orange-flower water and syrup, as No. 1.

3. (De vanille.) From essence of vanilla, 1 dr.; simple syrup, 1 pint.

Obs. The above are kept in small decanters, and used to flavour water, grog, liqueurs, &c., instead of sugar or capillaire; also to perfume the breath. Other flavoured syrups, for the same purposes, are prepared in a similar manner.

HU′MIC ACID. Syn. Ulmic acid. See Humus.

HUMULIN. The name given to a beautiful extract or essence of hops, made as follows:—

A concentrated tincture of hops is prepared by percolation with rectified spirit; the same hops are then exhausted with water; the spirit is removed from the tincture by careful distillation, and the upper aqueous portion is skimmed off, and added to the infusion, which latter is then evaporated to the consistence of a soft extract; the oleo-resinous residuum of the tincture is next added, and well mixed in; after which the whole is put into pots and carefully tied over for sale. The product possesses all the fragrant, tonic, and bitter qualities of the hop in a highly condensed form. See Hops, Lupulin, &c.

HU′MUS. Syn. Ulmin. When wood, or woody fibre, is exposed to the joint action of air and moisture, it suffers eremacausis or decay, and crumbles down into a dark-brown or black powder commonly called ‘mould,’ and to which chemists have given the name of ‘humus.’ In this state it exists in fertile soils, in which it is derived from the decay of plants. A powder of similar composition is produced by the action of powerful chemical reagents on sugar, lignin, &c. When acted upon by dilute boiling solution of caustic potassa, this substance yields a deep-brown solution, from which acids precipitate a flocculent brown substance generally called ‘ulmic’ or ‘humic acid.’ Both bodies require further investigation, as they are supposed to vary exceedingly in composition.

HUNGER. The peculiar sensation arising from the want of food. When severe, it increases to actual pain, the coats of the stomach are acted on by its own juices, the respiration becomes less frequent, the circulation languid, and there is a general diminution of the heat of the body and of the secretions. The return of hunger is accelerated by exercise and labour, and by the exposure of the body to a low temperature. Long fasting is injurious, more particularly to the young and the debilitated. See Appetite, Nutrition, &c.

HUS′BANDRY. The business of the farmer; by some the term is restricted to the joint operations of farming and gardening on the small scale. It is also sometimes used synonymously with agriculture.

HY′ACINTH. In botany, the English name for the genus Hyacinthus. There are numerous varieties of the garden hyacinth, all very beautiful. The bulbs are largely imported from Holland, and are often grown in water contained in suitable glass vessels (hyacinth glasses). In mineralogy, the term is applied to crystallised yellow or brown zircon. See Gems.

HYDRAC′IDS. Syn. Hydrogen acids. A name formerly given to those acids which do not contain oxygen, as hydrochloric, &c. It is still occasionally employed.

HY′DRAGOGUES. Syn. Hydragoga, L. Medicines which cause the removal of water from any of the cavities of the body. Many cathartics, as gamboge, jalap, &c., are classed under this head.

HYDRAS′TIN. The name given to a concentrated remedy much employed by the medical eclectics of America.

Prep. Treat the powdered root of golden-seal (Hydrastis Canadensis) with cold water by percolation; acidulate the infusion with hydrochloric acid; collect the precipitate on a filter; then dry it, dissolve the dried mass in alcohol, filter, and set aside to crystallise.

Prop. Yellow, acicular crystals, insoluble in cold alcohol, ether, and water.—Dose, 3 to 5 gr., 3 to 6 times a day; as a tonic in dyspepsia, inflammation of the stomach, &c.—Obs. According to the most recent investigations, hydrastin contains berberine, and another alkaline called hydrastia or hydrastina.

HYDRASTIS CANADENSIS. Syn. The Golden Seal. This is a small herbaceous perennial North American plant, belonging to the natural order, Ranunculaceæ. The rhizome, which is the officinal part, though yellow in the recent root, becomes of a dark yellowish-brown by age. It contains albumen, starch, fatty matter, resin, yellow colouring matter, sugar, lignin, and various salts; also a peculiar nitrogenous crystallisable substance, to which Dr Durand, the discoverer, proposed the provisional name of hydrastin, which substance will be found described below. The root of the golden-seal, as well as the alkaloids obtainable from it, are largely used in American medical practice, and are stated to possess valuable tonic, aperient, diuretic, and deobstruent powers. They have been employed in dyspepsia, jaundice, and functional disorders of the liver. They are also regarded as one of the best substitutes for quinine in intermittents.

Golden seal has been given in the form of infusion, decoction, tincture, and extract, and the fluid extract is now officinal in the United States’ Pharmacopœia.

HY′DRATES. Compounds of hydroxyl (HO) with other bodies, e.g. KHO—hydrate of potassium. The term hydrate is also given to chemical combinations of water (H2O) with other substances, e.g. C2HCl3O.H2O—hydrate of chloral.

HY′DRIDE. A compound of hydrogen with another radical, e.g. hydride of methyl—CH3H.

HYDRIO′DATE. A name formerly given to the salts now termed iodides. See Iodides.

HYDRIO′DIC ACID. Syn. Iodhydric acid; Acidum hydriodicum, L. An acid compound of iodine and hydrogen. See Iodine.

Prep. 1. By heating iodine in hydrogen, the volume of the gas becomes doubled, and a colourless acid gas is produced; it is, however, never prepared for use by this means. 2. Place 10 parts of potassic iodide in a small retort with 5 parts of water, and add 20 of iodide; then drop in cautiously one part of phosphorus, cut into small fragments, and apply a gentle heat. The gas will be given off abundantly and may be collected, by displacement, in dry bottles.

A solution of hydriodic acid may be prepared by suspending iodine in water, and passing a current of sulphuretted hydrogen through the mixture until the brown colour of the iodine disappears; sulphur is deposited in abundance, and hydriodic acid formed.

HYDRO′BENZANIDE. White crystalline mass, obtained from oil of bitter almonds by treatment with ammonia.

HYDROBRO′MIC ACID. See Bromide.

Hydrobromic Acid. (HBr.) Syn. Hydric Bromide, Hydrogen Bromide.

Prep. This very powerfully acid gaseous body may be prepared as follows:—1. By decomposing bromide of potassium with a concentrated solution of phosphoric acid. 2. By decomposing bromide of phosphorus by means of a small quantity of water.

Hydrobromic acid gas is colourless and non-inflammable; it extinguishes flame. It is extremely irritating to the lungs when breathed. It is very soluble in water.

HYDROBRO′MIDE. Syn. Bromide (which see).

HYDROCAR′BON. A compound of carbon and hydrogen. The hydrocarbons constitute a most important series of organic compounds.

HYDROCHLORIC ACID. (HCl = 36·5.) Syn. Muriatic Acid, Hydric Chloride, Hydrogen Chloride. This important gaseous compound was discovered by Priestly in 1772. In nature it is given off with other gases from active volcanoes, and is occasionally to be met with in the springs and rivers of volcanic districts. When hydrogen and chlorine are mixed in equal volumes, they are without action upon each other if kept in the dark, but if exposed to direct sunlight, chemical combination, accompanied by a loud explosion, instantly takes place between them, the result of their union being the colourless gaseous, intensely sour hydrochloric acid. If, instead of bright sunshine, the mixed gases are exposed to diffused daylight, chemical union also ensues between them, but the process is then a slow and gradual one; the passage through them, however, of the electric spark, or the application of a lighted match or taper instantly causes their explosion and combination.

One volume of chlorine unites with one volume of hydrogen, forming two volumes of hydrochloric acid; no condensation occurs in the act of union.

Hydrochloric acid may also be formed by transmitting moist chlorine through a red-hot porcelain tube; oxygen being at the same time liberated.

Prep. Hydrochloric acid, save for the purposes of illustrative experiment, is never obtained by any of the above processes. An easy mode of procuring it, when required for laboratory use, is to heat the ordinary aqueous solution of the acid in a flask, and to collect the gas, which is given off by displacement. It may also be readily got by introducing pieces of common salt (which should have been previously fused in a crucible at a red-heat and allowed to cool) into a glass retort, and pouring over them about twice their weight of oil of vitriol. The hydrochloric acid, which escapes very abundantly, must be collected either by displacement or over mercury.

Prop. Hydrochloric acid is a colourless gas, very acid to the taste, and irritating to the eyes; and induces coughing even if breathed in small quantities, or when largely diluted. It is very destructive to vegetation, on which account the soda manufacturer is compelled by law to condense and thus prevent the escape of its fumes. It has a specific gravity of 1·261. When subjected to a pressure of 40 atmospheres at 50° F., it becomes a colourless fluid capable of dissolving bitumen, and having a specific gravity of 1·27. It has never been frozen. Hydrochloric acid neither burns, nor supports combustion. The white fumes which it forms when exposed to the air, are due to its condensing the atmospheric moisture, and thus giving rise to a body less volatile than water. This gas is greedily and instantly absorbed by water. A fragment of ice placed in a jar of the gas absorbs it, and becomes immediately dissolved.

Hydrochloric Acid, Solution of. The hydrochloric acid of commerce is a solution of the above gas in water. When exposed to the air it emits grey fumes. Water at 40° F. absorbs about 480 times its bulk of hydrochloric acid, increasing in volume about one third in doing so, acquiring a density of 1·2109, and then containing nearly forty-three per cent. of the acid.

Strength of Solution of Hydrochloric Acid, 77° Fahr. (E. Davy.)

Sp. Gravity. Hydrochloric acid
in 100 parts. Sp. Gravity. Hydrochloric acid
in 100 parts.

1·21 42·43 1·10 20·20

1·20 40·40 1·09 18·18

1·19 38·38 1·08 16·16

1·18 36·36 1·07 14·14

1·17 34·34 1·06 12·12

1·16 32·32 1·05 10·10

1·15 30·30 1·04 8·08

1·14 28·28 1·03 6·06

1·13 26·26 1·02 4·04

1·12 24·24 1·01 2·02

1·11 22·22

In the laboratory, solution of hydrochloric acid is in constant use. It may be easily prepared from chloride of sodium and sulphuric acid. The retort should be connected with a couple of Woulfe’s bottles; into the first of which a small quantity of water should be poured, to detain any impurities mechanically carried over with the gas; the second bottle should contain four parts of water, and should be placed in a vessel of cold water, as the gas in becoming condensed, disengages a large amount of heat. The gas comes off and is absorbed readily by the water upon applying a gentle heat to the retort.

It is by this last method that solution of hydrochloric acid is obtained in such enormous quantities for the various purposes in which it is used, in the arts and manufactures.

Hydrochloric acid is, in fact, a by-product in the manufacture of carbonate of soda, and is generated during the first stage of the operation, known as the salt-cake process, which consists in the decomposition of salt by sulphuric acid, and is accomplished in a furnace called the salt-cake furnace.

The hydrochloric acid gas which is given off escapes from the furnace through a flue with the products of combustion into high brick towers filled with coke or stones, over which a stream of water trickles down, the whole of the acid vapours are thus condensed, the smoke passing off by a chimney connected with the towers. The diluted acid solution thus formed is concentrated by the aid of the apparatus shown in section in figs. 1, 2, and 3.

This apparatus consists of several cast-iron cylinders, 57 feet long by 27 feet in diameter, closed in the same manner as gas retorts, by lids luted with clay. One of the lids has an opening o, into which is fitted the stoneware or leaden pipe a, conveying the hydrochloric acid to the condensing apparatus. The other, or posterior lid, is also provided with an opening d, through which is passed the tube of a leaden funnel, so that after the retort is filled with salt sulphuric acid may be poured in. The construction of the furnace in which two retorts are usually placed, permits the flame of the fire at O to play round the cylinders before reaching the flue leading to the chimney F. B is an arch over the furnace. The first stage of the operation consists in filling each cylinder with 330 lbs. of salt. The lids or covers are then luted on, and the fire is kindled. The requisite quantity of strong sulphuric acid is next poured into the retort, and the funnel having been withdrawn from D, the hole is covered by a clay plug.

As soon as the reaction is over, the 396 lbs. of sulphate of soda produced are removed, and the operation repeated.

The condensation apparatus 1 and 3 is composed of rows of Woulfe’s bottles, partly filled with water, care being taken to place the first pairs of these bottles in a tank of cold water.

The condensation of the last portions of hydrochloric acid gas is effected either by the aid of the coke columns, or in leaden chambers, into which fine jets of cold water are injected on all sides.

“A saturated solution of hydrochloric acid in water has the specific gravity of 1·21; and when heated in a retort, loses at first hydrochloric acid gas, but after a time an aqueous acid distils over, at the ordinary atmospheric pressure, containing 20·22 per cent. of hydrochloric acid, and boiling constantly at 110° C. If the distillation be conducted under diminished pressure, the liquid boils at a lower temperature, and attains a composition which is different for each boiling point; hence the dilute acids thus obtained by boiling the solution of hydrochloric acid gas in water, cannot be considered as definite compounds of hydrochloric acid and water.”

Commercial hydrochloric acid is usually of a yellow colour owing to its being contaminated with iron. It also very frequently contains sodium, arsenic, sulphuric and sulphurous acids, and free chlorine.

Pure aqueous solution of hydrochloric acid should leave no residue upon evaporation; it should give no precipitation of ferric oxide when saturated with ammonia, sulphuretted hydrogen should cause no turbidity in it; if diluted with three or four times its volume of water, and chloride of barium be added, no white cloud or precipitate should form in the mixture; nor should the acid, if pure, discolour a fluid made faintly blue with iodide of starch.

Hydrochloric acid is largely consumed in the manufacture of chlorine, sal ammoniac, chloride antimony, glue, phosphorus, in the preparation of carbonic acid for the manufacture of artificial mineral waters, in beet-root sugar works, hydro-metallurgy, and alone, or mixed with nitric acid, for dissolving various metals. See Acids, Effects of Vegetation on, Chlorine.

HYDROCHLORIC ETHER. (C2H5Cl.) Syn. Ethyl Chloride, Chloride of Ethyl. This ether may be obtained either by saturating alcohol with hydrochloric acid gas, and then distilling at a gentle heat, or by distilling a mixture of three parts of oil of vitriol, two of alcohol, and four of fused chloride of sodium; the retort is in either case connected with a tubulated receiver, surrounded by water at a temperature of about 68° Fahr., in which most of the alcohol and water which pass over during the operation become condensed, whilst the ether escapes in the form of vapour through a bent tube, which is inserted into the tubulure of the receiver, and passes to the bottom of a flask kept cool with ice. The liquid which is condensed in the flask must be rectified from calcic chloride.

Hydrochloric ether is a colourless liquid, having a specific gravity at 32° Fahr. of 0·921, and a boiling point of 51·9° Fahr. The specific gravity of its vapour is 2·219. It has an ethereal, penetrating, somewhat garlicky odour. It is sparingly soluble in water, but readily so in alcohol. These solutions fail to give a precipitate with argentic nitrate.

HYDROCYANIC ACID. (HCN HCy.) Syn. Prussic acid, Hydric cyanide, Cyanhydric acid. Hydrocyanic acid was discovered by Scheele; but its nature and chemical properties were first investigated by Gay-Lussac.

Sources. This acid is found in water distilled from the kernels of the apricot, the peach, the plum, and cherry, the leaves of the laurel, and some other shrubs. The kernels of the bitter almond also yield it by distillation, mixed with an essential oil. The juice of the tapioca plant (the Jatropha manihot) likewise contains it. Many nitrogenous substances, when submitted to destructive distillation, also evolve hydrocyanic acid. Crystallised ammonic formiate subjected to heat in a retort yields a vapour which, passed through a red-hot tube, decomposes into this acid and water. Another method by which it may be obtained, consists in sending a current of dry sulphuretted hydrogen gas through a long tube filled with cyanide of mercury; and very recently it has been obtained by the direct combination of nitrogen and acetylene gas, by adding one volume of the former to two of the latter, and passing a series of electric sparks through the mixture, the gases combining without condensation. Lastly, it is yielded when a metallic cyanide or ferrocyanide is decomposed by an acid, this latter being the means by which it is invariably procured.

1. Anhydrous hydrocyanic acid may be prepared by Wöhler’s plan, which is as follows:—A crude potassium cyanide is prepared by fusing eight parts of the dried potassium ferrocyanide with three of potassium carbonate and one of charcoal.

The fused mass is treated with six times its weight of water in a well-closed vessel; the clear liquid is decanted from the iron, which it is the object of this operation to separate, and is poured into a retort: sulphuric acid, diluted with an equal weight of water, is gradually added in the proportion of one part of oil of vitriol to two parts of the cyanide. At first the distillation proceeds spontaneously from the heat developed by the admixture of sulphuric acid with the water. In order to condense the acid, the products are made to pass through a long U-shaped tube, immersed in cold water and filled with calcic chloride, with the exception of the first fourth of the tube, which contains fragments of the crude potassium cyanide; to the bent tube is attached a second delivery tube, which passes to the bottom of a bottle cooled with ice and salt. The calcic chloride in the syphon tube retains the moisture, and the potassic cyanide any sulphuric acid that might chance to pass over, whilst the hydrocyanic acid collects in the anhydrous state in the cooled receiver.

Trautwein recommends it to be prepared by the dehydration of the strong aqueous acid, by means of fused and pulverised chloride of calcium.

⁂ The observance of the greatest care and caution are necessary in the preparation of this most potent poison. The operation is most safely performed in winter. The apparatus should be so arranged as to allow of any vapours given off being carried from the operator by a brisk current of air.

Prop. At ordinary temperatures anhydrous hydrocyanic acid is a colourless liquid, having a specific gravity of 0·7058 at 44·6° Fahr. It is very inflammable, burning with a violet flame resembling that of cyanogen, but somewhat whiter in colour. It is soluble in all proportions in water, the resulting mixture being lighter than that fluid, and miscible with alcohol. It is very feebly acid; potassic cyanide always having an alkaline reaction. Red oxide of mercury is readily dissolved by it, and when added to a solution of argentic nitrate it precipitates white flocculi of cyanide of silver. Anhydrous hydrocyanic acid is an extremely volatile liquid; if a drop be let fall on a glass plate, part of it becomes frozen by the cold produced by its own evaporation.

2. Preparation of aqueous hydrocyanic acid.

a. From hydrated ferrocyanide of potassium.—By heating it in a glass retort with oil of vitriol and water, Everitt states that the best proportions are nearly ten parts of the salt to seven of oil of vitriol (diluted with any convenient amount of water). Adopting these proportions, 422·4 parts of ferrocyanide of potassium yield 81 parts of hydrocyanic acid. The greater part of the hydrocyanic acid passes over at the beginning of distillation, at a temperature a little above 212° Fahr.; and when the residual liquid reaches a higher temperature, the water (which then contains but little hydrocyanic acid) is then carried over. It is therefore necessary to employ a good condensing apparatus, or the hydrocyanic acid which passes over at first will for the most part be dissipated in vapour mixed with the air of the apparatus. This loss may also be obviated by placing water in the receiver. The residue need not be boiled down to dryness; it will be found best to distil off from two thirds to three fourths of the liquid, according to the amount of water present.

It is not necessary to dissolve the ferrocyanide in water previous to adding the sulphuric acid, as it readily dissolves in the water during the process of distillation.

Three conditions are important to be observed in the arrangements of the apparatus:—1. The mixture in the retort should not be allowed to spirt over. 2. It should contain but little air. 3. It should present the greatest possible amount of surface to be cooled.

If sulphate of potassium and prussian blue are spirted over into the distillate, this must be carefully rectified over a small quantity of magnesia, chalk, or carbonate of barium.

b. From cyanide of potassium (without distillation).—To a solution of nine parts of tartaric acid in sixty parts of water, contained in a well-stoppered bottle nearly filled with it, four parts of pure cyanide of potassium are added; the vessel is shaken, frequently dipped into cold water, and then left in the cold for twelve hours; and the aqueous hydrocyanic acid, which contains but a very small quantity of tartrate of potassium, is poured off from the crystallised tartrate. This acid contains 3·6 per cent. of anhydrous hydrocyanic acid.

c. From cyanide of mercury.—126 (accurately weighed) parts of cyanide of mercury are agitated with at least 28 parts of iron filings, in a well-stoppered bottle, containing 49, or rather more, parts of oil of vitriol, diluted with a considerable quantity of water. The agitation is continued until a portion of the liquid taken out is not blackened by sulphuretted hydrogen.

The solution, decanted from the iron and mercury, is then placed in a retort and distilled; the acid coming over at a gentle heat. Excess of iron accelerates the decomposition.

d. From cyanide of silver.—Everitt recommends 200 parts of pure cyanide of silver to be shaken up with 240 parts of hydrochloric acid of specific gravity of 1·129, and when the decomposition is complete, the hydrocyanic acid to be separated from the chloride of silver by decomposition.

This hydrocyanic acid may contain a small quantity of hydrochloric acid, a not very objectionable admixture, since it retards decomposition. It possesses the advantage of definite strength.

Prop. The aqueous is very similar in properties to the anhydrous acid, differing in taste, odour, poisonous and combustible properties, according to its degree of concentration. Like the anhydrous, the aqueous acid decomposes, but not so readily; when perfectly pure, becoming brown, and at last black. As before stated, a little free mineral acid assists to preserve it. It should be always kept in a dark place.

Detection and estimation of hydrocyanic acid and soluble cyanides.—The presence of hydrocyanic acid, indicated by the characteristic smell, which is given off by the contents of the stomach, or of any fluid containing it (provided this is not disguised by any substance of stronger odour) may be confirmed by the following tests:

1. To the filtered suspected fluid add a slight excess of caustic potash, and then a solution containing ferrous and ferric sulphates. If hydrocyanic acid, or a soluble cyanide be present, upon the addition of an excess of hydrochloric acid the liquid turns to a blue colour (more or less intense according to the quantity of acid present), owing to the formation of Prussian blue.

2. Add the suspected fluid solution of nitrate of silver; if hydrocyanic acid be present, a white cyanide of silver is formed, which is nearly insoluble in cold nitric acid, but is soluble in ammonia and cyanide of potash, and which, when heated to redness, gives off the inflammable violet-flamed cyanogen.

3. Acidulate a small quantity of the suspected liquid with a few drops of hydrochloric acid, and place it in a watch-glass; then invert a second watch-glass, moistened with a drop of solution of ammonic sulphide over this. After a few minutes remove the upper watch-glass, and evaporate the liquid to dryness over a water bath; let the dry residue be treated with a drop of a weak solution of ferric chloride. If hydrocyanic acid be present, a blood-red colour is produced, owing to the formation of red ferric hydrocyanide, which may be discharged by chloride of mercury; a reaction which distinguishes it from a similar colour given by meconic acid.

Where large quantities of material have to be examined, it is desirable that the acid should be distilled off by the heat of a water-bath, acidulating the liquid with tartaric acid if it be alkaline. The distillate is then to be tested by any of the above methods.

Antidotes.—Give a scruple of carbonate of potash dissolved in about an ounce of distilled water, and directly afterwards, ten grains of sulphate of iron, also dissolved in the same quantity of distilled water, to which should be added one drachm of tincture of perchloride of iron. Whilst this is being prepared, and subsequently, apply cold affusion to the head and neck, artificial respiration, and, if practicable, give strong coffee and brandy. A more ready remedy is ammonia, given both internally and applied to the nostrils.

Hydrocyanic Acid, Diluted. Syn. Acidum Hydrocyanicum Dilutum. (B. P.) The ‘British Pharmacopœia’ gives the following simple directions for the preparation of this acid:—

Dissolve two and a quarter ounces (avoir.) of ferro-cyanide of potassium in ten fluid ounces of distilled water, then add one fluid ounce of sulphuric acid, previously diluted with four fluid ounces of distilled water, and cooled. Put them into a retort and adapt this to a receiver, containing eight fluid ounces of water, which must be kept carefully cold. Distil with a gentle heat until the fluid in the receiver measures seventeen fluid ounces. Add to this three fluid ounces of the water, or as much as may be sufficient to bring the acid to the required strength of two per cent. by weight.

Prop. Specific gravity, ·997. 100 grains, or 110 minims, precipitated with a solution of nitrate of silver, give a precipitate of cyanide of silver, which when dried, weighs 10 grains. 270 grains rendered alkaline by liquor sodæ, require a 1000 grain measures of volumetric solution of nitrate of silver, before a permanent precipitate begins to form.

Antidotes. See Hydrocyanic Acid.

Hydrocyanic Acid, Scheele’s. Syn. Acidum Hydrocyanicum Scheelii. The original process of Scheele does not yield an acid of uniform strength, and is probably never followed. It is therefore impossible to state precisely what is intended when Scheele’s acid is prescribed, or to understand why it should be preferred by certain physicians to the British Pharmacopœia preparation, which is of a known and definite strength. As prepared by different makers it has been found to contain from three to five per cent. of anhydrous acid. The following is Scheele’s process:—

Mix two ounces of Prussian blue, with six ounces of red precipitate of mercury, and add six ounces of water. Boil for some minutes, constantly agitating; pour the whole on a filter and wash the residuum on the filter with two ounces of hot water, which is to be added to the filtered liquor. Add to this an ounce and a half of clean iron filings, and three drachms of sulphuric acid; shake well and let it settle; then pour the clear liquor into a retort, and distil a fourth part into a receiver well luted and kept cold.

HYDROFLUORIC ACID. (H. F.) Syn. Hydric Fluoride, Hydrogen Fluoride. Prep. 1. From fluor-spar (free from silica and metallic sulphides) and oil of vitriol. The fluor-spar being reduced to fine powder and placed in a leaden retort, is mixed with twice its weight of concentrated oil of vitriol, and on applying heat, an acid and highly acid vapour distils over, which condenses to a liquid if passed into a receiver of the same metal, standing in a freezing mixture at a temperature of 4° Fahr. Louyet has shown that the liquid acid, obtained as above, is not (as once believed) anhydrous.

2. From the double fluoride of potassium and hydrogen. Fremy first renders the salt anhydrous by careful drying; and by the subsequent application of a strong heat, expels the equivalent of hydrofluoric acid contained in it; condensing it into a colourless, mobile, very volatile liquid by the application of a freezing mixture of ice and salt.

3. By decomposing plumbic fluoride by dry hydrogen.

Prop. The strong, aqueous, hydrofluoric acid obtained by the action of oil of vitriol on fluor-spar, is a densely fuming, volatile, colourless liquid, which boils at 60° F., and remains unfrozen at 4°. It combines with water so greedily, and evolves so much heat in doing so, as to give rise to a hissing noise like that produced when a red-hot iron is plunged into cold water. In a concentrated form it has a specific gravity of 1·060. Brought into contact with animal matter of any kind it instantly destroys it, the smallest drop on the skin producing a deep and painful wound; hence the necessity of the greatest care in its preparation. With the exception of platinum, gold, silver, mercury and lead, hydrofluoric acid, when diluted, dissolves the metals, the metal when it undergoes solution, displacing hydrogen. Potassium decomposes the strong acid with explosion.

In both the gaseous and fluid form hydrofluoric acid is largely consumed for etching on glass; and this property constitutes one of its most available and reliable tests. The test may be conveniently applied as follows:—

Cover a small piece of window glass or a watch glass with a thin layer of wax, scraping away a very small portion by means of a sharply pointed instrument, and then expose the glass for a short time to the vapour of the acid, given off when the materials are heated in a small leaden saucer or platinum crucible; on removing the wax with a little turpentine, the marks on the glass caused by the hydrofluoric acid will be distinctly perceived.

HYDROFLUOSILIC′IC ACID. (4HF.SiF4.) Fluoride of silicon and hydrogen. Prep. From powdered fluor-spar, and siliceous sand or powdered glass, of each 1 part; concentrated sulphuric acid, 2 parts; mix in a glass retort, apply a gentle heat, and pass the evolved gas (fluoride of silicon) into water. Decomposition ensues, silica being deposited in a gelatinous state, and hydrofluosilicic acid remaining in solution. This acid liquor, which is a double fluoride of silicon and hydrogen, is used as a test for barium and potassium, with which it forms nearly insoluble precipitates.

HY′DROGEN. (H.) Syn. Hydrogenium, L. An elementary body discovered by Cavendish in 1766. It has been found existing in an uncombined state in the gases evolved from the solfataras of Iceland. Combined with oxygen, it constitutes water, and in this form is extensively distributed through earth, air, and ocean. It is an important constituent of all organised tissues.

Prep. Hydrogen is always obtained for experimental purposes by the deoxidation of water, by one or other of the following methods:—

1. A tube of iron or porcelain (a gun-barrel, for instance) containing a quantity of iron turnings or scraps of iron, is fixed across a furnace, so that its middle portion may be made red-hot; to the one end is attached a retort or other vessel containing water, and to the other a bent tube connected with a pneumatic trough or gasometer. The tube being now heated to redness, and the water in the retort brought into a state of brisk ebullition, the evolved steam suffers decomposition; the oxygen being absorbed by the iron, and the hydrogen escaping into the gas receiver.

2. Sulphuric acid (oil of vitriol), diluted with 6 or 8 times its bulk of water, is poured on granulated zinc (or scraps of iron) placed in a retort or gas bottle; hydrogen is evolved and is collected, as before.

Obs. This is the most convenient method of preparing hydrogen, and the one usually adopted in the laboratory. To ensure the gas being quite pure, distilled zinc is employed, and the gas is passed, first through a concentrated solution of pure potassa, then through a solution of nitrate of silver, and, lastly, through strong oil of vitriol, or over fragments of chloride of calcium. When hydrogen is prepared from crude zinc, it has a slight smell; and when from iron, its odour is often strong and disagreeable.

Prop. Gaseous; colourless; tasteless; odourless (when pure); combustible; sp. gr. ·06935, being 16 times lighter than oxygen gas, and 14·4 times lighter than atmospheric air. 100 cubic inches, at 60° Fahr. and 30 inches of the barometer, weigh 2·1371 (say 2·14) gr.; 1 gr. occupies 46·6 inches. It is very readily inflamed, even by a red-hot wire. It burns with a scarcely visible flame. Mixed with atmospheric air or oxygen, it explodes with extreme violence on the approach of flame, or sudden compression. One measure of hydrogen and 5 of atmospheric air, and 2 of hydrogen and 1 of oxygen, are the proportions that explode with the greatest violence. The combination of hydrogen and oxygen, when mixed, is brought about by the heat of a red-hot solid or a flame, by the electric spark, and by the presence of spongy platinum, the black powder of platinum, clean platinum foil, and some other substances. A jet of hydrogen burnt in oxygen gas, or a jet of these gases (mixed) burnt in the air, with proper precautions, produces a most intense heat. Water absorbs about 2% by volume of hydrogen.

Hydrogen has recently been liquefied and even solidified.

Tests. It is recognised by—its combustibility;—the pale colour of its flame;—producing water only when burnt in air or oxygen;—extinguishing the flame of other bodies; and—exploding when mixed with half its volume of oxygen, and fired.

Uses, &c. Pure and uncombined hydrogen is not employed in the arts. Inhalations of this gas have, however, been occasionally used in medicine. Dr Beddoes recommended them in phthisis. In combination, the uses of hydrogen are almost numberless. Combined with oxygen, it forms water; with chlorine, hydrochloric acid; with fluorine, hydrofluoric acid; with cyanogen, hydrocyanic acid; with carbon, innumerable hydrocarbons; with nitrogen, ammonia; with sulphur, sulphuretted hydrogen—in fact, an enumeration of the valuable compounds which it enters into would occupy many pages of this work. From its extreme lightness it has been used to fill balloons, but coal-gas is now commonly employed for this purpose. On its property of inflaming in contact with spongy platinum is arranged the popular little instrument for the production of instantaneous light (Dobereiner’s Lamp) sold by the philosophical instrument makers. The chemist avails himself of the great heat developed by its combustion in oxygen in the formation of the OXYHYDROGEN BLOWPIPE.

Some of the compounds of hydrogen are noticed below; the others under their respective names.

Hydrogen, Antimo′′niuretted. (SbH3.) Syn. Antimonetted hydrogen, Hydride of antimony, Stibamine; Hydrogenium antimoniatum, L. A gaseous compound of antimony and hydrogen, prepared by dissolving an alloy of antimony with a large excess of zinc in hydrochloric or dilute sulphuric acid. It has never been obtained pure, a variable proportion of free hydrogen being always present. It burns with a bluish-white flame, giving rise to dense fumes of teroxide of antimony, and when conducted through a red-hot tube, or the flame is thrown on a cold surface, as a porcelain plate, metallic antimony is deposited. This gas is a deadly poison when inhaled. See Arsenious acid.

Hydrogen, Arsen′′iuretted. (AsH3.) Syn. Arsenetted hydrogen, Hydride of arsenic, Arsenamine; Hydrogenium arseniuratum, L. A gaseous compound of arsenic and hydrogen.

Prep. Arsenide of zinc (made by fusing together equal weights of zinc and arsenic) is acted upon by strong hydrochloric acid or by sulphuric acid diluted with three parts of water.

Obs. This gas is produced whenever arsenious or arsenic acid, or any of their salts, is in presence of nascent hydrogen. The properties of arsenetted hydrogen are fully described in the tests for ARSENIOUS ACID. This gas is a deadly poison when inhaled.

Hydrogen, Car′buretted. Syn. Carbonetted hydrogen. This term is specially applied to two of the numerous compounds of carbon and hydrogen (CARBIDES OF HYDROGEN, HYDROCARBONS):—

1. Light Carburetted Hydrogen. (CH4.) Syn. Marsh gas, Fire-damp, Gas of the acetates. This is often abundantly disengaged in coal mines, and its combustion occasions those fearful explosions which are so destructive to human life. The mud at the bottom of stagnant pools, on being stirred, suffers bubbles of gas to escape, which, when collected and examined, are found to be a mixture of light carburetted hydrogen and carbonic acid. The latter is easily removed by passing the gas through a solution of caustic potassa or milk of lime.

Prep. (Dumas.) A mixture of acetate of soda (cryst.) and hydrate of potassa (dry), of each 2 parts, and quicklime (in powder), 3 parts, is strongly heated in a flask or retort. The gas in a state of absolute purity is disengaged in great abundance, and may be collected over water.

Prop. Colourless; neutral; nearly inodorous; burns with a yellow flame, producing pure water and carbonic acid; explodes when kindled in contact with air or oxygen.

2. Heavy Carburetted Hydrogen. (C2H4.) See Olefiant Gas.

Obs. Coal gas, OIL GAS, and RESIN GAS, consist, for the most part, of mixtures of these two gaseous hydrocarbons in uncertain proportions, obtained respectively from coal, oil, and resin, by the action of heat, and used for the purposes of illumination. See Gas.

Hydrogen, Oxides of. There are two well-defined compounds of hydrogen and oxygen:—

1. Subox′ide of Hydrogen. (H2O.) Water (which see).

2. Perox′ide of Hydrogen. (HO.) Syn. Hydroxyl, Binoxide of hydrogen, Deutoxide of H., Oxygenated water; Hydrogeniibinoxydum, L. This singular fluid was discovered by M. Thénard in 1818.

Prep. (Odling.) A known quantity of pure hydrochloric acid, diluted with 8 or 10 times its volume of distilled water, is placed in a glass beaker surrounded with ice or a freezing mixture. A quantity of binoxide of barium rather less than sufficient to neutralise the acid is then ground to a fine paste with distilled water, and added gradually to the acid in which it should dissolve without effervescence. Diluted sulphuric acid is next added cautiously, to precipitate the barium, and reproduce hydrochloric acid to act upon a fresh quantity of peroxide. The liquid having been filtered from the insoluble sulphate of baryta, a second proportion of binoxide of barium paste is added gradually, as before. The treatment with sulphuric acid, filtration and addition of binoxide, is repeated 6 or 7 times. Sulphate of silver is then very carefully added, so as exactly to precipitate in the form of chloride of silver the whole of the chlorine. After filtration, pure baryta, first as a paste and then in solution, is cautiously added, to precipitate exactly the sulphuric acid set free from the sulphate of silver. Filtration is again resorted to, and the clear liquid (aqueous solution of peroxide of hydrogen) is placed in a dish over oil of vitriol in vacuo, in order that the water mixed with it may evaporate.

Prop., &c. A colourless, transparent, somewhat syrupy liquid, of sp. gr. 1·452. It has a metallic taste, and corrodes the skin. It is easily resolved into oxygen and water. It mixes freely with water, and becomes more permanent by the dilution. It bleaches organic substances, and acts as a powerful oxidating agent. Under certain circumstances, however, it plays the part of a reducing agent. To the chemist, peroxide of hydrogen and its analogue, binoxide of barium, have been of great service as instruments of research. Binoxide of hydrogen has been applied in the arts to restore the blackened lights of paintings which have become darkened by sulphuretted hydrogen; it is also sold by hair-dressers for bleaching human hair.

Hydrogen, Phosphuret′ted. See Phosphorus.

Hydrogen, Sulphides of. See Sulphur.

HYDROMEL. Syn. Hydromeli, L. An aqueous solution of honey. Prep. (P. Cod.) Honey, 2 oz.; boiling water, 32 oz.; dissolve, and strain. A refreshing and slightly laxative drink; in fevers, hoarseness, sore throats, &c.

HYDROM′ETER. Syn. Areometer, Gravimeter; Hydrometrum, L. An instrument for ascertaining the specific gravities of liquids, and hence their strength, the latter being either in inverse or direct proportion to the former. Hydrometers are of two kinds:—1. Those which are always immersed to the same depth in distilled water, and the liquid to be tried, small weights being used for the purpose, as in Fahrenheit’s and Nicholson’s hydrometers; and 2nd, those which are suffered to rise or sink freely in the liquid, until they come to a state of rest, as in Syke’s, Baumé’s, &c. In both cases a correction must be made for any variation in temperature.

Of the two kinds, the first give the most accurate results, and have the great advantage of being applicable to liquids either lighter or heavier than water, but the second are the readier in practice, requiring less time and less skill to use them. The following are those best known:—

Baumé’s hydrometer or AREOMETER, which is very generally employed on the Continent, consists of two distinct instruments, the one for liquids heavier than water, the other for liquids lighter than that fluid. The first floats at the 0, or ‘zero,’ of the scale, in distilled wafer, at the temperature of 58° Fahr., and each degree, marked downwards, indicates a density corresponding to one per cent. of common salt. The hydrometer for liquids lighter than water is poised so that the 0 of the scale is at the bottom of the stem, when it is floating in a solution of 1 oz. of common salt in 9 oz. of water, and the depth to which it sinks in distilled water shows 10°; the space between these fixed points being equally divided, and the graduation continued upwards to the top of the scale.

The temperature at which these instruments were originally adjusted by Baumé was 12·5° Centigrade (54·5° Fahr.). They are now commonly adjusted in this country at 58° or 60° Fahr. Hence arise the discrepancies observable in the published tables of the “correspondence between degrees of Baumé and real specific gravities.”

Cartier’s hydrometer, which is much used in France for light liquids, has the same point for the zero of its scale as Baumé’s, but its degrees are rather smaller, 30° Baumé being equal to 32° Cartier.

Fahrenheit’s hydrometer consists of a hollow ball, with a counterpoise below, and a very slender stem above, terminating in a small dish. The middle, or half-length of the stem, is distinguished by a fine line across it. In this instrument every division of the stem is rejected, and it is immersed in all experiments to the middle of the stem, by placing proper weights in the little dish above. Then, as the part immersed is constantly of the same magnitude, and the whole weight of the hydrometer is known, this last weight, added to the weights in the dish, will be equal to the weight of fluid displaced by the instrument, as all writers on hydrostatics prove. And accordingly, the specific gravities for the common form of the tables will be had by the proportion—

As the whole weight of the hydrometer and its load, when adjusted in distilled water, is to the number 1000, so is the whole weight when adjusted in any other fluid, to the number expressing its specific gravity.

Gay-Lussac’s alcoholometer is used to determine the strength of spirituous liquors. It, at once, indicates on the stem, the per-centage of absolute alcohol in the liquid examined. The original experiments of Gay-Lussac having been made on liquids at a temperature of 59° Fahr., all examples examined by the alcoholometer, must either be brought to that temperature previous to being tested, or a correction made in the strength found.

Nicholson’s hydrometer is constructed on the same principle as Fahrenheit’s. It has in addition to the small dish for weights above, a little cup attached below, for holding any solid body whose weight in water is required. It is chiefly intended for taking the sp. gr. of minerals.

Richter’s hydrometer resembles, for the most part, Gay-Lussac’s.

Syke’s hydrometer is that adopted by the Revenue authorities in England for ascertaining the strength of spirits, and has been already fully noticed.

Tralles’s hydrometer resembles Gay-Lussac’s (nearly).

Twaddell’s hydrometer is much used in the bleaching establishments of Scotland, and in some part of England. According to this scale, 0 is equal to 1000 or the sp. gr. of distilled water, and each degree is equal to ·005; so that, by multiplying this number by the number of degrees marked on the scale, and adding 1·, the real specific gravity is obtained.

Obs. Hydrometers, unless manufactured with great care and skill, merely afford approximate results; but which are nevertheless sufficiently correct for all ordinary purposes. They also require several ounces of liquid to float them, and hence cannot be used for very small quantities. Those of Fahrenheit, Nicholson, and Sykes are the most accurate, both in principle and application. They are all employed with a tall glass cylinder termed a sample, test, or hydrometer glass, in the way already noticed; but the thermometer for ascertaining the temperature must be covered with a glass case, or arranged with a folding scale to allow of its immersion in corrosive liquids.

Alcoholometers, Elaiometers, Saccharometers, Urinometers, &c., are simply hydrometers so weighted and graduated as to adapt them for testing spirits, syrups, urine, &c. See Alcoholometry, Alonholmetry, Areometer, Specific Gravity, &c.

HYDROM′ETRY. Syn. Areometry. The art of determining the specific gravity of liquids, and hence their strength and commercial value. The instruments used are noticed above; their action depends upon the fact that a floating body displaces a bulk, equal to itself in weight, of the fluid in which it floats, and consequently that a body of a given weight sinks deeper in a lighter than in a heavier fluid. In hydrometric determinations the temperature of the samples must be carefully attended to, for fluids expand as their temperature is increased. The hydrometers used in England are generally adjusted to the standard temperature of 60° Fahr., and when ‘Hydrometer Tables,’ giving the corrections for the variations of the thermometer, are not accessible, the fluids to be examined should be brought to this standard temperature by applying heat directly to the vessel, when the temperature is below the standard, or by surrounding the vessel, with cold water, when it is above the standard. The principal applications of hydrometry are described in different parts of this work. See Acetimetry, Alcoholometry, Chlorometry, Specific Gravity, &c.

HYDROP′ATHY. Syn. Water cure; Hydropathia, L. A mode of curing diseases by the copious use of pure cold water, both internally and externally, together with dry sweating, and the due regulation of diet, exercise, and clothing. This “treatment of diseases undoubtedly includes powerful therapeutic agents, which, in the hands of the educated and honourable practitioner, might be most beneficially resorted to as remedial agents.” (Pereira.)

HYDROPHO′BIA. Syn. Canine madness; Rabies canina, L. A disease which is generally considered as the result of a morbid poison being introduced into the system by the bite of a rabid animal. A clear case of idiopathic or spontaneous hydrophobia has never yet been known to occur in the human subject.

The common symptoms of hydrophobia are great excitability and horror at the sight of water, or the attempt to drink, fever, vomiting, excessive thirst, spitting of viscid saliva, difficult respiration, irregular pulse, convulsions, syncope, delirium, and death.

The whole materia medica has been, unfortunately, unsuccessfully sought without the discovery of a single remedy for this disease, or even a palliative of its severer symptoms. See Curarine.

The treatment of recent bites of venomous animals has been fully explained, and need not be repeated here. To prevent secondary or constitutional effects arising, the use of lemon juice, or arsenical solution, has long been popular. (Graham, and others.) Dr Buchan remarks that “vinegar is of considerable use, and should be taken freely.”

HYDROSULPHU′RIC ACID. See Sulphur.

HYGIENE′. Syn. Hygiene, Fr. Health; its preservation, promotion, and restoration. That department of medicine and civil government which relates to health. See Air, Bath, Exercise, Flannel, Food, Nutrition, Sleep, Ventilation, &c.

HYGROMETER. An instrument for measuring the amount of moisture in the atmosphere.

Amongst the various contrivances for accomplishing this end are Daniel’s dew-point hygrometer; and the wet bulb hygrometer.

By the first, the quantity of moisture in the atmosphere, is determined by noting with a sensitive thermometer, the temperature at which a film of dew mass, to deposit on one of the bulbs of a species of cryophorus, disappears; the tension of the aqueous vapour present in the air at that period, being readily ascertained from tables constructed for the purpose, the corresponding proportion of moisture can thus be readily ascertained.

The wet bulb hygrometer consists of two small thermometers placed side by side, the bulb of them being surrounded by cotton films kept constantly damp by a simple contrivance. According to the rate of evaporation of the bulb so moistened, with the fall of the thermometer to which the moistened bulb belongs, the depression, of course, being greater the further the surrounding atmosphere is from the saturation point, and tables are furnished for determining the degree of saturation for all differences of temperature within the ordinary atmospheric range.

HYOCHO′LIC ACID. C25H40O4. Syn. Glycohyocholalic acid. A compound peculiar to the gall of pigs, discovered by Strecker and Gundelach.

Prep. The fresh gall of pigs is mixed with a solution of sulphate of sodium; the precipitate is dissolved in absolute alcohol, and decolourised by animal charcoal. From this solution ether throws down hyocholate of sodium, which, on the addition of sulphuric acid, yields hyocholic acid as a resinous mass, which is dissolved in alcohol, re-precipitated by water, and dried. When heated with alkaline solutions, glycocine and a new crystalline acid (hyocholalic acid) are formed. When boiled with acids, it yields glycocine and hyodyslysin.

HYOSCY′AMINE. Syn. Hyoscyamia, Hyoscyamina, Daturine, Daturia. An alkaloid obtained from common henbane (Hyoscyamus niger), and also from the thorn apple (Datura stramonium). See Datura.

HYPNOT′ICS. Syn. Hypnotica, L. Agents or medicines which induce sleep, as opium, morphia, henbane, Indian hemp, lactucarium, &c. Agents which prevent sleep are called agrypnotics (Agrypnotica, L.), or anthypnotics (Anthypnotica, L.).

HYPOCHLO′RIC ACID. See Chlorine.

HYPOCHONDRI′ASIS. Syn. Hypochondriacism. The ‘hip’ or ‘hyp,’ the ‘vapours,’ depression of spirits, ‘blue devils.’ This disease chiefly affects persons of the melancholic temperament, and is commonly induced by hard study, irregular habits of life, want of proper social intercourse, living in close apartments, and insufficient out-of-door exercise. The treatment may, in most cases be similar to that recommended for DYSPEPSIA, observing, however, that success depends more on amusing and engaging the mind, and in gradually weaning it from old conceits, than in the mere administration of medicine. When the patient is tormented with a visionary or exaggerated sense of pain, or of some concealed disease, or a whimsical dislike of certain persons, places, or things, or groundless apprehensions of personal danger or poverty, or the conviction of having experienced some dreadful accident or misfortune, the better way is to avoid any direct attempts to alter his opinions, but to endeavour to inspire confidence in some method of relief. Greding mentions the case of a medical man who conceived that his stomach was full of frogs, which had been successively spawning ever since he had bathed, when a boy, in a pool in which he had perceived some tadpoles; and he had spent his life in endeavouring to get them removed. One patient, perhaps, fancies himself a giant; another as heavy as lead; a third a feather, in continual danger of being blown away by the wind; and a fourth a piece of glass, and is hourly fearful of being broken. Marcellus Dentatus mentions a baker of Ferrara who thought himself a lump of butter, and durst not sit in the sun, or come near the fire, for fear of being melted. The writer of this article once knew a man who always put on his coat the wrong side in front, because he conceived his face looked behind him. In such cases it is useless to argue with the patient, as it only causes irritation, and increases the malady. The restoration of the bodily health, and a sudden surprise or change of scene, will often effect a cure.

HYPONI′TRIC ACID. See Nitrogen.

HYPONI′TROUS ACID. See Nitrogen.

HYPOPHOS′PHITES. See Phosphorus.

HYPOPHOS′PHITE. A salt of hypophosphorous acid.

HYPOSUL′PHATE. Syn. Dithionate; Hyposulphas, L. A salt of hyposulphuric acid.

HYPOSUL′PHITE. Syn. Thiosulphate; Hyposulphis, L. A salt of hyposulphurous acid.

HYPOSUL′PHUROUS ACID. See Sulphurous Acid.

HYRA′CEUM. A substance produced by the Cape badger (Hyrax Capensis), and proposed as a substitute for CASTOREUM. Pereira considered it to be inert and useless.

HYSTERICS. Syn. Hysteria, Passio hysterica, L. In pathology, a nervous affection peculiar to women, attacking in paroxysms or fits, preceded by dejection; tears, difficult breathing, sickness, and palpitation of the heart. The treatment of this disease varies with the causes and the symptoms. Bleeding, cupping, and depletives, are generally had recourse to in robust and plethoric habits, and stimulants and tonics in those of a weakly or relaxed constitution. Affusion of cold water and nasal stimulants will frequently remove the fit in mild cases. Exercise, proper amusements and regular hours and diet, are the best preventives. See Draught (Antihysteric and Hydrocyanic), &c.

ICE. Syn. Glacies, L. Water in the solid state. On being cooled, water gradually contracts until the temperature has fallen to 39·9° Fahr., when it begins to expand. At the freezing-point, 32° Fahr., under ordinary conditions, water crystallises or freezes, and in consequence of the continued expansion, the sp. gr. of ice, as compared with that of water at 39·9°, is as ·94 to 1·00. Ice has the peculiar property of reuniting by the contact of adjoining surfaces after having been broken into fragments (REGELATION). Coloured water and salt water, by freezing, produce colourless and fresh ice; and clean solid ice, when thawed, furnishes water equal in purity to that which has been distilled.

The use of ice in the preparation of ICE-CREAMS, ICED-LIQUORS, &c., is noticed elsewhere. The confectioner collects his ice as early as possible during the winter, and stores it in a well-drained well or excavation, somewhat of the form of an inverted sugar-loaf, contained in a small shed or building called an ICE-HOUSE. This building should always be situated on a dry sandy soil, and, if possible, on an eminence. The door should be on the north side, and the roof should be conical and thickly thatched with straw.

In medicine, ice is frequently employed externally in inflammation of the brain, to resolve inflammation, to stop hæmorrhage, to constringe relaxed parts, and an anodyne, to deaden pain. For these purposes it is pounded small, in a cloth, and placed in a bladder or bag of gauze (ICE-CAP, ICE-POULTICE) before applying it. Internally, ice or ice-cold water has been given with advantage in heartburn, typhus, inflammation and spasms of the stomach, to check the vomiting in cholera, and to arrest hæmorrhage, whether bronchial, gastric, nasal, or uterine. Very recently, ice has been proposed as a remedy in the treatment of diphtheria. Small lumps of ice, or a small glassful of pounded ice-and-water, will often temporarily restore the tone of the stomach and nervous system during hot weather, when all other means fail. Ice-creams, taken in moderation, act in the same way.

In the warmer climates of Europe an ICE-HOUSE or an ICE-SAFE (a REFRIGERATOR) is a necessary appendage to every respectable dwelling, not merely for the purpose of pleasing the palate with iced beverages, but to enable the residents to preserve their provisions (fish, meat, game, milk, butter, &c.) in a wholesome state from day to day. In addition to large cargoes of ice imported yearly from Norway, and principally consumed in England, Germany and France, ice is now manufactured to no inconsiderable amount, in these three countries artificially, the principal consumption of the factitious article being by brewers, who use it for the cooling of their worts. The artificial manufacture of ice is effected by the means of the condensation of elastic vapours in machines expressly made for the purpose. In Siebe’s ice-making machine the vapour of ether is made to traverse metallic tubes surrounded with a concentrated solution of common salt, by which it becomes recondensed to the liquid state, to be again utilised in the production of the vapour; the solution of salt becoming at the same time so reduced in temperature, as to convert into ice, water, contained in proper vessels, placed in it. In Carré’s machine the same end is accomplished by means of ammoniacal gas, a solution of calcic chloride being used for absorbing the cold instead of common salt. Reece’s is a modification, (he states an improvement) of Carré’s. Ice machines are also made, in which ice is produced, by bringing water into contact with air, which has been greatly reduced in temperature by cooling it when in the compressed state, and subsequently allowing it to expand. Liquid carbonic and sulphurous acids have likewise been used in the preparation of artificial ice, but not when it has been required in any considerable quantity. See Refrigeration.

Ice, Medicated. Mr Martin, of Weston-super-Mare, writing to the ‘Lancet,’ says:—“Every practitioner has at times to face the difficulties of the scarlatinal throat in young children. It may sadly want topical medication; but how is he to apply it? Young children cannot gargle, and to attempt the brush or the spray fills them with terror. In many cases neither sternness nor coaxing avails. Yet these little ones in almost every case will greedily suck bits of ice. This has long been my chief resource where I could not persuade the child to submit to the sulphurous acid spray. Lately, I have been trying an ice formed of the frozen solution of the acid (or some other antiseptic). Though, of course, not so tasteless as pure ice, the flavour is so much lessened by the low temperature, and probably also through the parched tongue, very little appreciating any flavour, that I find scarcely any complaint on that score from the little sufferers; they generally take to it very readily. The process of making it is very simple. A large test-tube immersed in a mixture of ice and salt is the only apparatus required, and in this the solution is easily frozen. When quite solid a momentary dip of the tube in hot water enables one to turn out the cylinder of ice, as the cook turns out her mould of jelly. I have tried the three following formulæ, all of which answer, although I think I prefer the first.

“1. Sulphurous acid, ⁄2 dr.; water, 7⁄2 dr.; mix and freeze.

“2. Chlorate of potass, 1 scruple; water, 1 oz.; dissolve, and freeze.

“3. Solution of chlorinated soda, ⁄2 dr.; water, 1 oz.; mix and freeze.

“However, the form is of secondary importance, as each practitioner can construct his own. Boracic acid, salicylic acid, or any other harmless antiseptic with not too much taste, would doubtless be as useful as those indicated.”

ICE′LAND MOSS. Syn. Cetraria (B. P.), Lichen Islandicus, L. The lichen termed Cetraria Islandicus. It is much employed, both as a nutritious food and as a mild mucilaginous tonic, in catarrh and consumption. It may be purified from its bitter principle by a little cold solution of potassa.

Iceland Moss, Saccharated. Syn. (P. C.), Saccharum lichenis. Iceland moss, 1 lb.; refined sugar 1 lb.; macerate the moss in water to extract the bitterness, express, boil in water for an hour, strain, let settle, decant, add the sugar, evaporate to dryness with a gentle heat, constantly stirring, and finally reduce to powder.

ICES. (In confectionery.) These are commonly composed of cream or sweetened water, variously flavoured, and congealed by ice or a freezing mixture. Sometimes, instead of cream, the materials of a custard are used. The mixed ingredients are placed in a tin furnished with a handle at top, called a ‘freezer,’ or ‘freezing-pot,’ which is then plunged into a bucket containing ice broken small, and mixed with about half its weight of common salt, and is kept in rapid motion, backwards and forwards, until its contents are frozen. As the cream congeals and adheres to the sides, it is broken down with the ice-spoon, so that the whole may be equally exposed to the cold. As the salt and ice in the tub melt, more is added, until the process is finished. The ‘ice-pot,’ with the cream in it, is next placed in a leaden ‘ice-stand,’ is at once surrounded with a mixture of ice and salt, and closely covered over. In this state it is carried into the shop. The glasses are filled as required for immediate use, and should have been previously made as cold as possible.

Plain ice-cream, or CREAM FOR ICING, is commonly made by one or other of the following formulæ:—

1. New milk, 2 pints; yolks of 6 eggs; white sugar, 4 oz.; mix, strain, heat gently and cool gradually.

2. Cream 1 pint; sugar, 4 oz.; mix as above.

3. Cream and milk, of each 1 pint; white sugar, ⁄2 lb.

Flavoured ice-creams are made by mixing cream for icing with half its weight of mashed or preserved fruit, previously rubbed through a clean hair sieve; or, when the flavour depends on the juice of fruit or on essential oil, by adding a sufficient quantity of such substances. Raspberry and STRAWBERRY ICES are made according to the former method; LEMON, ORANGE, NOYEAU, and ALMOND ICES, by the latter method. In the same way any other article besides cream may be frozen.

Chocolate for icing is made by rubbing 1 oz. of chocolate to a paste with a tablespoonful of hot milk, and then adding ‘cream for icing,’ 1 pint.

Coffee for icing is made of cream for icing, 1 quart, to which a small teacupful of the strongest possible clarified coffee has been added together with 2 oz. of sugar and the yolks of 3 or 4 eggs. See Icing (below).

I′CING. (For cakes.) Syn. Sugar ice. The covering of concreted sugar with which the confectioners adorn their cakes. Prep. Beat the white of eggs to a full froth, with a little rose or orange-flower water; then add gradually, as much finely powdered sugar as will make it thick enough, beating it well all the time. For use, dust the cakes over with flour, then gently rub it off, lay on the icing with a flat knife, stick on the ornaments while it is wet, and place it in the oven for a few minutes to harden, but not long enough to discolour it. It may be tinged of various shades by the addition of the proper ‘stains.’

ID′RIALIN. A fusible, inflammable substance, found associated with the native cinnabar of the mines of Idria, in Carniola. It is extracted from the ore by means of oil of turpentine. It is only slightly soluble in alcohol and ether. When pure, it is white and crystalline.

ID′RYL. A hydrocarbon generally found associated with idrialin.

IGASU′RIC ACID. Syn. Acidum igasuricum, L. An acid associated with strychnine in the St. Ignatius’ bean and in nux vomica. It may be obtained by digesting the rasped or ground beans first in ether and then in boiling alcohol, evaporating the latter decoction to dryness, diffusing the residuum through water, adding a little carbonate of magnesium, again boiling for some minutes, filtering, washing the powder with cold water, and digesting it in alcohol, and filtering. The igasurate of magnesium thus obtained is dissolved in boiling water, the solution decomposed by acetate of lead, and the precipitate (igasurate of lead), after being washed and diffused through distilled water, is decomposed by sulphuretted hydrogen. The solution thus obtained yields crystals (igasuric acid) on being evaporated. It is soluble in both water and alcohol.

IGNI′′TION. In the laboratory this term is commonly applied to the act of heating to redness or luminousness. See Calcination.

ILLICIN. Boil a clear decoction of holly with animal charcoal; let it settle, collect the deposited charcoal, wash it with cold water, dry it, and treat it with boiling alcohol; let the filtered liquid be evaporated to dryness. Febrifuge.—Dose, 6 to 24 gr.

ILLUMINA′TION. The act of illuminating or making luminous. For supplying artificial light to streets and the interiors of houses coal gas and oils and fats are generally employed. These illuminating agents are compounds rich in carbon, upon the presence of which the brightness of their flames depends. Flame is gas or vapour heated to incandescence during the process of combustion. A flame containing no solid particles emits but a feeble light, even if its temperature is the highest possible. Pure hydrogen, for instance, burns with a pale, smokeless flame, though with the production of considerable heat. On the other hand, wax, paraffin, coal-gas, &c., while undergoing combustion, give out considerable light, because their flames contain innumerable solid particles of carbon, which act as radiant points. To give the greatest degree of luminosity to flame, the supply of air must be proportioned to the character of the burning substance, and be insufficient for the instantaneous combustion of the evolved gases; in which case the hydrogen takes all the oxygen, and the larger portion of the carbon is precipitated, and burnt in the solid form, at some little distance within the outer surface of the flame. When the supply of air is sufficient for the immediate and complete combustion of the whole of the combustible matter, no such precipitation takes place, and the flame is neither white nor brilliant. The richest coal-gas, mixed with sufficient air to convert all its hydrogen and carbon into water and carbonic acid, explodes with a pale blue flash; yet the same gas, when consumed in the ordinary way, burns with a rich white flame. Every one must have noticed the effect of a gust of wind upon the flaring gas-jets of a butcher’s shop; the plentiful supply of air causes complete combustion, and so converts the bright white flames into dull blue streaks of fire. When the supply of air is insufficient to cause the combustion of the newly formed solid carbon at the instant of its development, and whilst it is in an incandescent state, the flame becomes red and smoky, and unburnt sooty particles are thrown off. The same occurs when the temperature of any portion of the hydrogen is reduced below that intensity required for the combustion of the newly separated charcoal. Solid bodies, as tallow, oils, and fats, which burn with flame, are converted into the state of gas by the heat required to kindle them, and it is this gaseous matter which suffers combustion, and not the substance which produces it.

The relative value of the ordinary illuminating agents has been accurately determined by Dr Frankland. According to his experiments, the quantities of various substances required to give the same amount of light as would be obtained from 1 gallon of Young’s Paraffin oil are as follows:—

Young’s Paraffin oil 1·00 gall.

American rock oil 1·26 ”

Paraffin candles 18·6 lbs.

Sperm 22·9 ”

Wax 26·4 ”

Stearic 27·6 ”

Composite 29·5 ”

Tallow 39·0 ”

The following table exhibits the comparative cost of the light of 20 sperm candles, each burning 10 hours at the rate of 120 gr. per hour; also the amount of carbonic acid produced and heat evolved per hour, in obtaining this quantity of light:—

Cost.

s. d. Carb. acid per hour
in cub. feet. Units of heat per hour.

Wax 7 2⁄2 8·3 82

Spermaceti 6 8

Paraffin candles 3 10 6·7 66

Tallow 2 8 10·1 100

Rock oil 0 7⁄2 3·0 29

Paraffin oil 0 6

Coal gas 0 4⁄2 5·0 47

Cannel gas 0 3 4·0 32

These figures prove that coal-gas and the mineral oils are the cheapest and best illuminating agents, producing the largest amount of light with the least development of heat.

The light emitted by incandescent lime (Drummond light, HYDRO-OXYGEN LIGHT, LIME LIGHT, OXYHYDROGEN LIGHT) is intensely brilliant, and is often made use of to enable workmen to continue operations at night. It is obtained by directing the flame produced by the combustion of a mixture of hydrogen (or coal-gas) and oxygen upon a small cylinder of lime. In the improved form of this light the lime is protected from crumbling by a cage of platinum wire, and is caused to rotate slowly by means of clockwork, so as constantly to expose a fresh surface to the flame. When reflected from a ‘parabolic mirror’ in a pencil of parallel rays, the Drummond light has been recognised during daylight at a distance of 108 miles. The lime light produced with coal-gas and oxygen is used for the MAGIC LANTERN and GAS MICROSCOPE.

The most powerful illuminator is the ELECTRIC LIGHT, which is now being subjected to trial in many cities for street illuminations, &c., in place of coal-gas. It is usually produced by the passage of a strong current of electricity between two pencils of hard carbon. The electric light has been successfully applied to lighthouse illumination. Hitherto it has been found too intense and too costly for application to domestic purposes. See Candles, Flame, Gas, Photometry, &c.

ILLU′TATION. See Bath (Mud).

IMAGINA′TION. The influence of the imagination, both in the production and cure of disease, has been long admitted by medical practitioners. It is probably the most powerful therapeutic agent known. “Extraordinary cures have been ascribed to inert and useless means, when, in fact, they were referable to the influence of the imagination.” (Dr Pereira.)

IMPE′RIAL. Syn. Potus imperialis, Ptisana i., L. Prep. 1. Cream of tartar, ⁄4 oz.; 1 lemon, sliced; lump sugar, 2 oz.; boiling water, 1 quart; infuse, with occasional stirring until cold, then pour off the clear portion for use.

2. A lemon, sliced; sugar, 1 oz.; boiling water, 1 pint.

3. Yellow rind and juice of lemon; citric acid, 1 dr.; sugar, 2⁄2 oz.; hot water (which has been boiled), 1 quart; as No. 1. Refrigerant and slightly diuretic. Used as a common drink in fevers, dropsy, &c., and as a summer beverage.

IM′PLEMENTS (Agricultural). “Almost all the operations of agriculture may be performed by the plough, the harrow, the scythe, and the flail; and these are the sole implements in the primitive agriculture of all countries. With the progress of improvement, many other implements (and machines) have been introduced, the more remarkable of which are the Drill plough, the HORSE HOE, the WINNOWING MACHINE, the THRESHING MACHINE, the HAY-MAKING MACHINE, and the REAPING MACHINE. The object of all these implements and machines is to abridge human labour, and to perform the different operations to which they are applied with a greater degree of rapidity, and in a more perfect manner than before.” (Loudon.) On the perfection of agricultural implements and machines depends much of the improvement of which this art is susceptible. See Agriculture, &c.

IMPROV′ING. The trade name for ‘doctoring,’ ‘adulterating,’ or ‘lowering,’ the quality of any substance, with the view of cheapening it or increasing its bulk. See Wine, &c.

IN′CENSE. Prep. 1. Olibanum, 2 or 3 parts; gum benzoin, 1 part.

2. Olibanum, 7 parts; gum benzoin, 2 parts; cascarilla, 1 part. Placed on a hot plate or burned, it exhales an agreeable perfume. Used in some of the rituals of the Roman Catholic church.

3. Benzoin and storax, of each 4 oz.; labdanum and myrrh, of each 6 oz.; cascarilla 3 oz.; oil cinnamon, 8 minims; oils bergamot and lavender, of each 20 minims; oil cloves, 10 minims; mix, and pass through a coarse sieve.

INCINERA′TION. The reduction of organic substances to ashes by combustion. See Calcination.

INCOMBUSTIBIL′ITY. The property of being incapable of being kindled, or of being consumed by fire. Substances possessing this property are said to be ‘incombustible’ or ‘fire-proof.’

INCOMBUST′IBLE FAB′RICS. Syn. Non-inflammable fabrics. The fashion of wearing light gauzy dresses extended by hoops or crinoline has made death from fire a common casualty. With a view of diminishing the danger to which women expose themselves, chemists have lately devoted considerable attention to the problem of rendering muslin and other light fabrics non-inflammable. This object may be attained by steeping the fabric in almost any saline solution. Thus, cotton or linen stuffs prepared with a solution of borax, phosphate of soda, phosphate of ammonia, alum, or sal ammoniac, may be placed in contact with ignited bodies without their suffering active combustion or bursting into flame. The salts act by forming a crust of incombustible matter on the surface of the fibres. They do not, however, prevent carbonisation taking place, when the temperature is sufficiently high. It is by a knowledge of this property of culinary salt that jugglers are enabled to perform the common trick of burning a thread of cotton while supporting a ring or a small key, without the latter falling to the ground. The cotton is reduced to a cinder, but from the action of the salt its fibres still retain sufficient tenacity to support a light weight.

The addition of about 1 oz. of alum or sal ammoniac to the last water used to rinse a lady’s dress, or a set of bed furniture, or a less quantity added to the starch used to stiffen them, renders them uninflammable, or at least so little combustible that they will not readily take fire; and if kindled, are slowly consumed without flame. None of the above-named salts are adapted for fine soft muslins, which mostly require chemical treatment, because they injure the texture, rendering the fabric harsh and destroying all its beauty. The salt which is found to answer most completely all the required conditions is TUNGSTATE OF SODA. “Muslin steeped in a solution containing 20% of this salt is perfectly non-inflammable when dry, and the saline film left on the surface is smooth and of a fatty appearance like talc, and therefore does not interfere with the process of ironing, but allows the hot iron to pass smoothly over the surface. The non-fulfilment of this latter condition completely prevents the use of many other salts—such as sulphate or phosphate of ammonia, which are otherwise efficacious in destroying inflammability—for all fabrics which have to be washed and ironed.” (Watts.)

The addition of a little phosphoric acid or phosphate of soda to the tungstate is recommended, for without this addition a portion of the tungstate is apt to undergo a chemical change and become comparatively insoluble. Messrs Versmann and Oppenheim, the introducers of tungstate of soda, give the following formula for a solution of minimum strength:—

Dilute a concentrated solution of neutral tungstate of soda with water to 28° Twaddell (sp. gr. 1·14), and then add 3% of phosphate of soda. This solution is found to keep and to answer its purpose very well; it is now constantly used in the Royal Laundry.

Paper, WOOD, &c., may be also rendered comparatively incombustible by soaking them in saline solutions. See Asbestos, Fire, &c.

INCOMPAT′IBLES. In medicine and pharmacy, substances which exert a chemical action on each other, and cannot, therefore, with propriety, be prescribed together in the same formula or prescription. The principles on which we should act to avoid prescribing or dispensing incompatibles, are briefly developed under the heads Affinity and Decomposition. To this we may add that, if a substance is endowed with well-marked therapeutical or poisonous properties, independent of those which may exert a chemical effect upon the tissues, its mode of action will neither be changed nor destroyed by the combinations which it forms, provided always that the new compounds are not insoluble in water.

“It is not necessary to give two incompatible medicines at the same time, in order to produce decomposition; it is sufficient if they are given within a very short interval of each other. Thus, a sick person, who has been treated with lead externally, or even internally, will present a discoloration of the skin, if he takes a sulphur bath four or five days after the lead treatment has been discontinued. If a person is rubbed with iodide of potassium shortly after having applied Vigo’s plaster (plaster of ammoniacum with mercury), or the Neapolitan ointment (mercurial ointment), iodide of mercury and caustic potash will be formed, which will cause vesication. So also vomiting occurs if lemonade made with tartaric acid is taken five or 6 days after the administration of white oxide of antimony.” (Trousseau and Reveil.)

Lists of incompatibles are published in many pharmaceutical and medical works, but are, in reality, of little use beyond illustrating rules and principles which are familiar to every chemist, and which every prescriber should also be intimately acquainted with.

INCRUSTATION, Prevention of, in Steam Boilers. With all qualities of water commonly used for feeding steam boilers there is a tendency to the production of hard calcareous deposits or layers of incrustation within the boilers, due to the separation of lime salts (particularly the carbonate and sulphate, or mixtures of these with a certain amount of carbonate of magnesia) as the direct consequence of the accumulation of these impurities from large quantities of water evaporated. The sparing solubility of the sulphate of lime (gypsum) in hot water fully accounts for its deposition in the boiler, and the carbonate of lime (chalk) is thrown down, not only as the result of direct evaporation, but by the ebullition expelling free carbonic acid, which holds this body to some extent in solution. Rain water, which of itself is too pure to give rise to these incrustations, cannot be used alone for boiler purposes, for it has been found to exert a highly corrosive action upon the iron plates and fittings. It can, however, be advantageously employed in conjunction with ‘hard’ spring or river waters, and has the effect of diminishing the incrustation merely as the result of dilution. The drain pipes leading from the roof of the factory may be placed in connection with the tank or well from which the supply of water is drawn for the boilers. It will be seen hereafter that the self-same remedy is efficient both as a means of preventing incrustation and obviating corrosion, and that by using one of the alkaline substances about to be specified this twofold advantage may be secured. Iron will not rust when immersed in water containing a mere trace of caustic alkali, and it is a common observation that the iron vessels used in the preparation of potash and soda remain for any length of time free from all appearance of rust. This singular property is, no doubt, susceptible of important applications, amongst them may be mentioned the better protection of iron ships from the attack of bilge water, of hydraulic rams, moulding boxes, smith’s tools, and other objects liable to be placed at times under the influence of water. Some forms of surface condensers become quickly corroded in consequence of the purity of the water accumulating in them by the process of distillation, and a small dose of caustic alkali is then useful as a means of protection; the engine-cylinders also to some extent are preserved when alkaline anti-incrustation fluids are introduced into the boilers, for the minute quantity which is carried forward mechanically in the form of spray mixed with the steam, suffices to preserve the iron. Whilst a tendency to ‘priming’ undoubtedly results from a too liberal use of soda or other alkali in the boiler, it will in practice be found easy to adjust the proportion of this ingredient, so as to secure immunity from corrosion and incrustation, and at the same time, avoid the tumultuous kind of ebullition known as ‘priming.’ In all cases it is advisable to carry out a rigid system of inspection, and it is only in the way of saving fuel and labour that the application of boiler fluids is to be recommended.

Much benefit has often resulted from a coating of coal-tar or ‘dead oil’ applied to the interior surfaces below the water line, when the boiler is opened for cleaning and inspection. These will tend very considerably to lessen the adhesion of calcareous crusts, and are not in any way affected by the boiler fluids in common use. Soda crystals and caustic soda may be used with great success in boilers to effect the immediate precipitation of the lime salts, and they act by throwing down a finely divided form of carbonate of lime, which in time furnishes nuclei for the deposition of subsequent accretions both of the carbonate and sulphate, so that they are prevented from crystallising upon the walls of the boiler. A granular mud is thus formed, which subsides quickly and may be for the most part got rid of through the ‘blow-off cock,’ which should be opened for this purpose two or three times every day, and run out with as little water as possible.

The use of caustic soda has undergone a thorough trial at the hands of Mr J. Spiller, F.C.S., in the boilers of the Royal Arsenal, Woolwich, and we are favoured with the following general instructions regarding its use, which are based upon an experience of upwards of ten years. The caustic soda should be dissolved in water so as to make a concentrated solution of specific gravity 1·300. This, being perfectly miscible with water, may be introduced into the boiler with the feed-water at any time when, from the pressure of steam, it may not be convenient to pour it through the safety valve or other openings in the boiler. But when the steam is down there is no difficulty in introducing the prescribed dose by using a tin funnel with flattened aperture to pass it through the safety valve; or a tubular arrangement with double cocks will answer at all times. Half a gallon per diem is the average quantity found sufficient for a 20-horse stationary boiler, working with Thames water for ten hours daily. If the water should happen to be unusually hard a larger dose may be employed, but it would not be expedient to add in one charge more than the amount required for the day’s consumption. Locomotive and multitubular boilers have been worked successfully with caustic soda, and it is here that the importance of using anti-incrustation fluids makes itself most apparent.

Many other methods have at various times been proposed to prevent the formation of deposits in steam boilers. Dr Ritterband’s method consists in simply throwing a little sal ammoniac into the boiler, by which carbonate of ammonia is formed, which passes off with the steam, and chloride of calcium, which remains in solution. In Holland this plan has been used with satisfaction for locomotive boilers. About 2 oz. of the salt may be placed in the boiler twice a week. The chloride of tin is equal to sal ammoniac, and is similar in its action. Carbonate of soda has been recommended by Kuhlmann and Fresenius of Germany, and by Crace Calvert of England. It is now employed generally in the boilers of engines in Manchester. The common plan adopted by working engineers to prevent incrustations from either variety of water is, on each occasion of cleaning out the boiler, to introduce some substance which, by its mechanical action, shall prevent the precipitated earthy matter caking together, or adhering to the boiler plates. Some common tar, bitumen, or pitch, appears to answer well under most circumstances. Mr Ira Hill recommends the use of 3 or 4 shovelfuls of course sawdust. He states that, after adopting the use of this article, he never had any difficulty from lime, although using water strongly impregnated with it, and has always found the inside of his boilers as smooth as if just oiled. Mr De Haen recommends the sulphate and bicarbonate of calcium to be decomposed by adding barium chloride and milk of lime in the proper proportion; when the water is at a temperature of 35°-45° C. the whole becomes clear in about ten minutes, a precipitate consisting of a mixture of barium sulphate and calcium carbonate deposits; if the water be cold, the greater part separates in ten minutes, but a little turbidity is noticeable for some hours due to suspended matter.

Protzen recommends the introduction of a piece of zinc into the boiler, this determines a galvanic current, which protects the iron against oxidation and corrosion, and causes the mineral ingredients of the water to be deposited as a fine loose mud, entirely preventing the formation of incrustation.

Slippery elm bark, and spent bark from the tan works have also been suggested. We (A. J. Cooley) have worked a powerful boiler daily for months without opening the ‘man-hole,’ after throwing a few pounds of potatoes into it. In all cases, when the earthy matter can be kept in a state of solution, or precipitated in a pulverulent form, it is easily removed from the boiler by what engineers term ‘priming,’ which is allowing the hot water to be blown over with the steam, so that, after a sufficient time, the whole original contents of the boiler are removed, and replaced by fresh water. Before doing so, however, it is of consequence to cut off the communication with the cylinders, and to open the waste-steam cock. Consult a pamphlet on ‘Boiler Incrustation and Corrosion’ by F. J. Rowan, published by Spon, London.

INCUBA′TION (Artificial). The hatching of eggs by artificial heat. This has been practised by the Egyptians from a very remote period. M. Bonnemain has the honour of having introduced this art to Western Europe, in 1775, and having been the first to pursue it successfully on the commercial scale. The source of heat employed by him was a circulatory hot-water apparatus, and the temperature maintained by it 100° Fahr. His plan was to introduce, daily, 1-20th only of the eggs the apparatus was capable of receiving, so that on the 21st day the first chickens were hatched, and a like number every day afterwards as long as the supply of eggs was kept up. Among the trays containing the eggs he placed saucers of water, to compensate for the absence of moisture derived in natural incubation by transpiration from the body of the hen. The chickens, as soon as hatched, were transferred to a ‘nursery’ or ‘chick-room,’ also artificially heated, and were fed with crushed millet seed. Several attempts have been made of late years to introduce artificial incubation into this country, with variable success.

IN′CUBUS. See Nightmare.

IN′DIA RUB′BER. See Caoutchouc.

INDIGES′TION. See Dyspepsia.

IN′DIGO. Syn. Indicum, Pigmentum Indicum, L. A blue dyestuff extracted from several plants growing in India and America, especially from the leguminous species Indigofera tinctoria and I. cœrulea. It exists in the plant as a colourless juice. The method of manufacture consists in steeping the plant in water until fermentation sets in; the colouring matter dissolves in the water, forming a yellow solution, which is drawn off from the rest of the vegetable matter, and agitated and beaten to bring it freely into contact with the air for about 2 hours; this treatment causes the indigo to form and settle down as a blue precipitate; this is cut, while soft, into cubical cakes, and dried by artificial heat. To hasten the formation of the indigo, a little lime water is sometimes added to the yellow solution. The indigo of commerce contains INDIGO-BLUE or INDIGOTIN, its most important constituent, INDIGO-RED, and many other substances, some of which must be regarded as accidental impurities or adulterations.

Prop. Tasteless; scentless; of an intense blue colour, passing into purple; when rubbed with a smooth hard body, it assumes a coppery hue; insoluble in water, cold alcohol, ether, alkalies, hydrochloric acid, dilute sulphuric acid, and the cold fixed and volatile oils; slightly soluble in boiling alcohol and oils; freely soluble in concentrated sulphuric acid, and, when decoloured or reduced by contact with deoxidising substances, in alkaline lyes; soluble in creasote; its colour is destroyed by chromic acid, nitric acid and chlorine; when suddenly heated, it gives off rich purple fumes, which condense into brilliant copper-coloured needles.

Pur. The best indigo is that which has the deepest purple colour, that assumes the brightest coppery hue when rubbed with the nail; its fracture is homogeneous, compact, fine-grained, and coppery; its powder is of an intensely deep blue tint, and light enough to swim on water; and it leaves only a fine streak when rubbed upon a piece of white paper. In general, when indigo is in hard, dry lumps of a dark colour, it is considered of bad or inferior quality. Indigo, when in hard or brittle lumps, or in dust or small bits, is often adulterated with sand, pulverised slate, and other earthy substances.

Estimation. Various methods for estimating the value of samples of indigo have been proposed, but none of them can be depended upon to give perfectly accurate results. The plan recommended by O′Neill is perhaps the best; it is performed as follows:—

Weigh 25 gr. of a fair sample of the indigo finely ground; and to soften or disintegrate it still further, boil it for a short time with weak caustic soda, and then, if there be any soft lumps or clots, strain through calico; mix this with 3 quarts of water in a narrow-necked bottle which it will nearly fill, and add 400 gr. of quicklime, which has been slaked as perfectly as possible; shake well up and add a 1000 gr. measure of solution of green copperas (protosulphate of iron) at 30° Twaddell; cork the bottle closely, and leave it for three days, frequently shaking it in the interval. The indigo will be dissolved by this time; 1 quart of the clear solution is drawn off, shaken up in a bottle to oxidise it, acidified with acetic acid, and the pure indigo (INDIGOTIN) collected upon a filter, dried, and weighed. Four times the weight of the pure indigo is the per-centage of indigo in the sample.

Uses. As a dye stuff indigo is of great importance, both from the beauty and permanence of the colour it yields, and from the ease with which it is applied to fabrics of all materials. As a medicine it has been employed in various affections of a spasmodic character, as chorea, convulsions, epilepsy, hysteria, &c. In large quantities it often induces giddiness, vomiting, and diarrhœa; and when continued for sometime, muscular twitchings, resembling those arising from strychnine.—Dose. Beginning at about 15 gr., and gradually increased to 1, 2, or even 3 dr., at which it should be continued for 3 or 4 months; made into an electuary with honey or sugar, to which some aromatic may be added. See Indigo Dye, Indigotin, &c.

Indigo, Sul′phate of. Syn. Sulphindylic acid, Sulphindigotic a., Saxony blue, Soluble indigo.

Prep. By gradually adding indigo (in fine powder), 1 part, to fuming sulphuric acid (Nordhausen sulphuric acid), 5 parts, or oil of vitriol, 8 parts contained in a stone-ware vessel placed in a tub of very cold water, to prevent the mixture heating; the ingredients are stirred together with a glass rod at short intervals until the solution is complete, after which the whole is allowed to repose for about 48 hours, by which time it becomes a homogeneous pasty mass of an intense blue colour, which in a dull light appears nearly black.

Obs. In this state it forms ‘Barth’s blue,’ or the ‘CHEMIC BLUE’ or ‘INDIGO COMPOSITION’ of the dyer. Diluted with about twice its weight of soft water, it is converted into the ‘Saxony blue’ or ‘LIQUID BLUE’ of the shops, also used for dyeing. When commercial sulphate of indigo is diffused through a large quantity of water, nearly boiling, and wool (old white flannel rags, &c.) is macerated in it for some time, the latter absorbs the whole of the sulphate and is dyed blue, whilst the liquor assumes a greenish-blue colour. Wool, so prepared, when well rinsed in cold water, and boiled for some minutes in a large quantity of that liquid containing 1% or 2% of carbonate of potassa, or a quantity equal to about 1-3rd that of the indigo originally employed, gives up its blue colour, and becomes of a dull brown. The liquid is now a rich blue-coloured solution of sulphindylate of potassa, from which the salt may be obtained by cautious evaporation. This compound is prepared on the large scale, by diluting sulphate of indigo with about 12 times its weight of soft water, and imperfectly saturating the solution with carbonate of potassa; the sulphindylate falls down as a dark-blue coppery-looking powder, soluble in 140 parts of cold water and in about 90 parts of boiling water. This substance is kept both in the moist and dry state, and is known in commerce under the respective names of ‘DISTILLED INDIGO,’ ‘PRECIPITATED INDIGO,’ ‘SOLUBLE INDIGO,’ ‘INDIGO PASTE,’ ‘BLUE CARMINE,’ ‘DISTILLED BLUE,’ ‘SOLUBLE BLUE,’ &c. It is extensively used in dyeing; and when mixed with starch, whilst in the moist state, and made into cakes or knobs, it constitutes the finest variety of the ‘BLUE’ used by laundresses for tinging linen. The ammonia and soda salts may be prepared in the same way as the potassa salt, by substituting the carbonates of those bases for carbonate of potassa. The ammonia salt is very soluble.

INDIGO BLUE. See Indigotin.

INDIGO DYE. There are two methods of preparing solutions of indigo for dyeing.—1. By deoxidising it, and then dissolving it in alkaline menstrua.—2. By dissolving it in sulphuric acid. The former method is used in preparing the ordinary INDIGO VAT of the dyers.

1. a. (Cold vat.) Take of indigo, in fine powder, 1 lb.; green copperas (clean cryst.), 2⁄2 to 3 lbs.; newly slaked lime, 3⁄2 to 4 lbs.; triturate the powdered indigo with a little water or an alkaline lye, then mix it with some hot water, add the lime, and again well mix, after which stir in the solution of copperas, and agitate the whole thoroughly at intervals for 24 hours. A little caustic potassa or soda is frequently added, and a corresponding portion of lime omitted. For use, a portion of this ‘preparation vat’ is ladled into the ‘dyeing vat,’ as wanted. After being employed for some time, the vat must be refreshed with a little more copperas and fresh-slaked lime, when the sediment must be well stirred up, and the whole thoroughly mixed together. This is the common vat for cotton.

b. (Potash vat.) Take indigo, in fine powder, 12 lbs.; madder, 8 lbs.; bran, 9 lbs.; ‘potash,’ 24 lbs.; water at 125° Fahr., 120 cubic feet; mix well; at the end of about 36 hours add 14 lbs. more potash, and after 10 or 12 hours longer further add 10 lbs. of potash, and rouse the whole up well; as soon as the fermentation and reduction of the indigo are well developed, which generally takes place in about 72 hours, add a little fresh-slaked lime. This vat dyes very quickly, and the goods lose less of their colour in alkaline and soapy solutions than when dyed in the common vat. It is well adapted for woollen goods.

c. (Wood vat.) As the last, but employing wood instead of madder; the vat is ‘set’ at 160° Fahr., and kept at that temperature until the deoxidation and solution of the indigo has commenced. The last two are also called the ‘warm vat.’

d. (Pastel vat.) This is ‘set’ with a variety of wood which grows in France, and which is richer in colouring matter than the plant commonly known as ‘wood.’

e. (Schützenberger and De Lalande’s vat.) It is known that the low stage of oxidation of sulphur obtained on the reduction of sulphurous acid with zinc, dissolves indigo. On this reaction the following proceedings for dyeing and printing with indigo are founded:—To prepare the reducing liquid, a solution of bisulphite of soda at 35° B. is brought in contact with sheet zinc in a closed vessel, of which the liquid should occupy only one fourth. After the lapse of an hour the zinc is precipitated from the clear liquid by means of milk of lime. It is then diluted or decanted, or filtered with exclusion of air.

The clear liquid is then poured upon the ground indigo, with the addition of the needful soda and lime. One kilo of indigo yields in this manner a very concentrated vat of from 10 to 15 litres. Cotton is dyed cold, and wool with the aid of heat. A vat is filled with water, and a suitable quantity of the above indigo mixture introduced, when the dyeing can be performed at once. The excess of the low sulphur acid dissolves the froth which appears on the surface. During the process of dyeing, further quantities of indigo can be added as required. Cotton can be rapidly and easily dyed in this manner; and in the case of wool, the dyer escapes the many disadvantages of the hot vat and obtains brighter and clearer shades. To print a fast blue the alkaline solution of the reduced indigo is printed on with an excess of the reducing agent, aged for twelve to twenty-four hours, washed and soaped. In comparison with the old process there is a saving of indigo to the extent of 50 to 60 per cent.; the shades are richer and the impressions sharper. The colour requires no subsequent treatment, and can therefore be printed on simultaneously with most other colours.

Obs. Wool, silk, linen, and cotton, may each be dyed blue in the indigo vat. The goods, after being passed through a weak alkaline solution, are subjected to the action of the vat for about fifteen minutes; they are then freely exposed to the air; the immersion in the vat and the exposure are repeated until the colour becomes sufficiently deep. Wood and madder improve the richness of the dye. Other deoxidising substances, besides those above mentioned, may be used to effect the solution of the indigo; thus a mixture of caustic soda, grape sugar, indigo, and water, is often employed on the Continent for this purpose; and orpiment lime, and pearlash are also occasionally used. When properly prepared, the indigo vat may be kept in action for several months by the addition of one or other of its constituents, as required. An excess of either copperas or lime should be avoided.

2. Solution of sulphate of indigo is added to water, as required, and the goods, previously boiled with alum, are then immersed in it, and the boiling and immersion are repeated until the wool becomes sufficiently dyed.