Chapter II: REDUCTION OF SOLUTIONS:--The reduction of the solution to the proper (11)

2. (Hosp. Form.) Chlorinated solution of soda, 4 fl. dr.; water to 4 fl. oz. Used as the last.

=Gargle of Chlo''rine Water.= _Syn._ GARGARISMA CHLORINII, L. _Prep._ 1. (Fr. Hosp.) Chlorine water, 1/2 fl. oz.; syrup, 1 fl. oz.; water, 4-1·2 fl. oz.

2. (Mid. Hosp.) Chlorine water, 2 fl. oz.; distilled water, 10 fl. oz. _Use._ As the last.

=Gargle of Cincho'na Bark.= _Syn._ GARGARISMA CINCHONÆ, L. _Prep._ 1. From decoction of cinchona, 7 fl. oz.; simple oxymel, 1 fl. oz. Antiseptic and astringent in relaxation, &c.

2. (Acidulated; GARGARISMA CINCHONÆ ACIDUS, L.) Hydrochloric acid, 1-1/2 fl. dr.; honey, 1-1/2 oz.; decoction of bark to make up 8 fl. oz.

=Gargle, Com'mon.= _Syn._ GARGARISMA COMMUNE, L. _Prep._ 1. (Ed. Hosp.) Water, 6 fl. oz.; nitre, 1 dr.; honey of roses, 1 oz. For ordinary sore throat, &c.

2. (Lond. Hosp.) Alum, 1 dr.; dilute sulphuric acid, 2 fl. dr.; tincture of myrrh, 4 fl. dr.; water to 12 fl. oz.

=Gargle of Cy'anide of Mercury.= _Syn._ GARGARISMA HYDRARGYRI CYANIDI, L. _Prep._ 1. (Brera.) Cyanide of mercury, 10 gr.; honey of roses, 1 oz.; barley water, 1 pint.

2. (Cullerier.) Cyanide of mercury, 10 gr.; linseed tea, 1 pint. Used in the same cases as mercurial gargle.

=Gargle, Deter'gent.= _Syn._ GARGARISMA DETERGENS, L. _Prep._ 1. (P. Cod.) Alcoholised sulphuric acid, 1 fl. dr.; honey of roses, 2 oz.; barley water, 8 oz.

2. (Dr A. T. Thomson.) Nitre, 2 dr.; honey of roses, 4 fl. dr.; infusion of roses, 5-1/2 fl. oz. In inflammatory sore throat.

=Gargle, Emol'lient.= _Syn._ GARGARISMA EMOLLIENS, L. _Prep._ 1. (Buchan.) Marshmallow root, 1 oz.; figs, 2 oz.; water, 1 quart; boil to a pint and strain. Demulcent, soothing.

2. (Trousseau & Reveil.) Barley water, 8 oz.; honey, 1-1/2 oz. Both are used in inflammatory affections of the throat and mouth.

=Gargle of Horserad'ish.= _Syn._ GARGARISMA ARMORACIÆ, L. _Prep._ (Collier.) Compound spirit of horseradish, 1 fl. oz.; honey, 2 oz.; water, 4 fl. oz. A good gargle for scurvy of the fauces and pharynx, vulgarly called the 'inward scurvy.'

=Gargle of Hydrochlo''ric Acid.= _Syn._ MURIATIC ACID GARGLE; GARGARISMA ACIDI HYDROCHLORICI. L. _Prep._ 1. (Guy's Hosp.) Hydrochloric acid, 30 drops; honey of roses, 2 oz.; barley water, 6 fl. oz.

2. (Ratier.) Hydrochloric acid, 2 fl. dr.; clarified honey, 2 fl. oz.; barley water, 1 pint.

3. (St. B. Hosp.) Red-rose leaves, 2 dr.; boiling water, 1 pint; hydrochloric acid, 1-1/2 fl. dr.; digest 1 hour, and strain. In inflammatory sore throat, ulcerations of the mouth, scarlet fever, &c.

=Gargle of I'odine.= _Syn._ GARGARISMA IODINII, L. _Prep._ 1. Iodine, 10 gr.; iodide of potassium, 12 gr.; rectified spirit and simple syrup, of each, 1 fl. oz.; water, 5 fl. oz. In chronic enlargement of the tonsils, in scrofulous habits.

2. (Dr Ross.) Tincture of iodine, 1-1/2 fl. dr.; tincture of opium, 1 fl. dr.; water, 6 fl. oz.

3. (St. T. Hosp.) Compound tincture of iodine, 2 fl. dr.; water, 5 fl. oz. In ulceration of the tonsils.

=Gargle, Mercu''rial.= _Syn._ GARGARISMA HYDRARGYRI, G. MERCURIALE, L. _Prep._ 1. (G. HYD. BICHLORIDI.) Corrosive sublimate, 2 to 5 gr.; barley water, 1 pint; honey of roses, 2 fl. oz. For syphilitic ulcers in the throat.

2. (Plenck.) Calomel, 6 gr.; quicksilver, 30 gr.; powdered gum, 3 dr.; syrup of poppies, 1/2 oz.; triturate till the globules of metal disappear, and add of decoction of clematis, 26 fl. oz.; honey of roses, 1 oz.; essence of myrrh, 1 dr. (or tincture of myrrh, 1 fl. oz.). In syphilitic and putrid sore throat.

=Gargle of Mustard.= _Syn._ GARGARISMA SINAPIS. _Prep._ (Fleury). Black mustard seed, bruised 4 ounces; salt, 4 scruples; vinegar, 8 scruples; warm water, 7 ounces. Digest and filter.

=Gargle of Myrrh.= _Syn._ GARGARISMA MYRRHÆ, L. _Prep._ 1. (Ainslie.) Tincture of myrrh, 6 fl. dr.; vinegar, 1 fl. dr.; honey of roses, 1-1/2 fl. oz.; barley water, 12 fl. oz.

2. (Ph. Chirur.) Tincture of myrrh, 1/2 oz.; honey of roses, 1-1/2 oz.; lime water, 6 fl. oz. In scarlatina and putrid sore throat. See ASTRINGENT GARGLE, &c.

=Gargle of Ni'tre.= _Syn._ GARGARISMA SALIS NITRI, G. POTASSÆ NITRATIS, L. _Prep._ 1. Nitre, 2 dr.; honey or syrup, 1/2 oz.; rose water, 5-1/2 fl. oz.

2. (Brande.) Nitre, 2 dr.; oxymel, 1 fl. oz.; barley water, 7 fl. oz. In inflammatory sore throat. See COMMON GARGLE.

=Gargle of Oak-Bark.= _Syn._ GARGARISMA CORTICIS QUERCÛS, L. _Prep._ 1. Oak-bark, 2 dr.; boiling water, 6 fl. oz.; macerate 1 hour, and strain.

2. (Ellis.) Decoction of oak-bark, 1 pint; alum, 1/2 dr.; brandy, 2 fl. oz. In chronic sore throat, relaxation of the uvula, &c.

=Gargle of Oxide of Manganese.= _Syn._ GARGARISMA MANGANESII OXIDI. _Prep._ (Pareira). Black oxide of manganese, 2 dr.; decoction of barley, 5 fl. oz.

=Gargle of Pel'litory.= _Syn._ GARGARISMA PYRETHRI. _Prep._ 1. Pellitory root, 4 dr.; water, 16 fl. oz.; boil to 8 fl. oz., and add of liquor of ammonia 2 fl. dr.

2. (Swediaur.) Infusion of pellitory, 1 pint; vinegar, 3 fl. oz.; sal-ammoniac, 3 dr. To promote the maturation and healing of throat ulcers.

=Gargle of Permanganate of Potash.= _Syn._ GARGARISMA POTASSÆ PERMANGANATIS. _Prep._ (Throat Hosp.) Solution of permanganate of potash (B. P.), 6 minims; distilled water, 1 fl. oz. Antiseptic.

=Gargle of Ro''ses.= _Syn._ GARGARISMA ROSÆ, G. ROSARUM, L. _Prep._ (Kendrick.) Conserve of roses, 3 oz.; boiling water, 16 fl. oz.; infuse 1 hour; add of dilute sulphuric acid, 2 fl. dr., and strain. Antiseptic, astringent; used in several indications.

=Gargle of Subacetate of Lead.= _Syn._ GARGARISMA PLUMBI SUBACETATIS. _Prep._ (Ratier.) Liquid subacetate of lead, 1/2 dr.; barley water, 1 lb.; syrup, 1 fl. oz.

=Gargle of Turpentine.= _Syn._ GARGARISMA TEREBINTHINATUM. _Prep._ (Geddings.) Oil of turpentine, 2 dr.; mucilage, 6-1/2 fl. oz. In salivation.

=Gargle, Spirit.= _Syn._ GARGARISMA SPIRITUOSUM, G. SPIRITÛS VINI, L. _Prep._ 1. (Dr Watson.) French brandy, 1 fl. oz.; water, 1/4 pint.

2. (St. George's.) Proof spirit, 1 fl. oz.; oxymel, 5 fl. dr.; decoction of barley, to make up 6 fl. oz. In relaxations and salivation.

=Gargle, Stim'ulant.= _Syn._ GARGARISMA STIMULANS, L. _Prep._ (Dr Copland.) Infusion of roses, 6-1/2 fl. oz.; dilute hydrochloric acid, 40 drops; tincture of capsicum, 1-1/2 fl. dr.; honey, 3 dr. See GARGLE OF CAPSICUM.

=Gargle of Tan'nin.= _Syn._ GARGARISMA ACIDI TANNICI, L. _Prep._ 1. (Beral.) Tannin, 1 dr.; honey of roses, 2 oz.; rose water, 2 fl. oz.; distilled water, 8 fl. oz.

2. (Jannart.) As the last, but using only half the quantity of tannin. In salivation and aphthous ulcerations.

=Gargle of Verd'igris.= _Syn._ GARGARISMA ÆRUGINUS, G. CUPRI ACETATIS, L. _Prep._ (Guy's Hosp.) Oxymel of verdigris, 4 dr.; honey of roses, 2 oz.; barley water, 3-1/2 fl. oz. Used as a detergent for ulcers in the throat. If swallowed it produces violent vomiting. The addition of 2-1/2 oz. of water to the above produces a gargle sufficiently strong for most cases.

=Gargle of Vin'egar.= See GARGLE OF ACETIC ACID.

=Gargle of Zinc.= _Syn._ GARGARISMA ZINCI, G. Z. SULPHATIS, L. _Prep._ (Dr Copland.) Sulphate of zinc, 20 gr.; oxymel, 1 fl. oz.; rose water, 7 fl. oz. In aphthous sores, relaxations, ulceration of the tonsils, &c.

=GAR'LIC.= _Syn._ ALLIUM, L. The _Allium sativum_ of botanists. It is diaphoretic, diuretic, expectorant, stimulant, and tonic; and externally, irritant, rubefacient, and even vesicant.--_Dose_, 1/2 dr. to 1-1/2 dr.; in enfeebled digestion, chronic diarrh[oe]a, old chronic coughs, atonic dropsies, and worms. An antispasmodic and counter-irritant liniment is made of the juice, which was formerly esteemed in chest diseases and infantile convulsions. A small clove of garlic, or a few drops of the juice, was formerly introduced into the ear in certain forms of deafness. As a condiment its properties resemble those of the onion, than which it is much more powerful.

=GAR'NET.= In _mineralogy_, one of the precious stones or gems. The finest specimens of noble garnet (SYRIAN or ORIENTAL GARNET) are brought from Pegu. According to chemical analysis, the garnet is a double silicate of alumina and lime, coloured with iron and manganese.

=Garnet, Facti''tious.= See PASTES.

=GA'RUM.= [L.] A species of pickle or sauce prepared of fish, in a state of incipient putrefaction, strongly salted and seasoned with aromatics. According to Pliny, the Romans used a species of lobster for this purpose.

=GAS.= _Syn._ GAZ, Fr. A permanently elastic aëriform fluid. In English the term 'air' is now usually restricted to the gaseous mixture forming the atmosphere, but it was formerly used as a synonym for 'gas.' The principal gases are the elementary bodies hydrogen, chlorine, oxygen and nitrogen, and the compounds ammonia, carbonic acid, carbonic oxide, carburetted hydrogen, hydrochloric acid, phosphoretted hydrogen, protoxide of nitrogen, sulphuretted hydrogen, and sulphurous acid. See these substances under their respective heads.

=Gas.= _Syn._ COAL GAS, ILLUMINATING G. The term 'gas' is popularly applied to the important mixture of hydrocarbons produced by the destructive distillation of pit-coal, and now employed as a source of artificial light in most of large towns of Europe and America. Although artificial illumination by means of coal-gas was, previous to 1819, used in Great Britain in isolated cases, and had been employed for the occasional lighting up of the mansion of Culrose Abbey in Scotland, by Lord Dundonald, as far back as 1787; and by Murdoch, in 1798, for lighting the foundry of Boulton and Watts in Soho, it does not appear to have been generally adopted in London, and the other large towns of England and Scotland until that year; since which time to the present artificial gas illumination has steadily progressed, and increased to so enormous an extent, that some works are now delivering millions of cubic feet of coal-gas a day. The apparatus used in the manufacture of gas on the large scale consists essentially of a system of closed retorts (_a_) of cast iron or fire-clay, generally having the form of a flattened cylinder, and arranged in sets of three or five, and heated by the same coal fire, as shown in the accompanying drawing.

The quantity of coal required to charge each retort is about two bushels, and it takes about four hours for the coal to give off all its gas. When it has done this the resulting coke is removed from the retort, and a fresh charge of coal is thrown into it, the mouth of the retort being then closed with a thick iron plate, and luted with clay. An iron pipe ascends from the upper side of the front of the retort, projecting from the furnace, and after describing a curve at its upper extremity, this iron pipe opens into a much wider tube, called the _hydraulic main_ (_b_), which latter passes horizontally along the front of the range of furnaces, the tubes from all the retorts dipping into it. The hydraulic main is always kept half full of the water and the tar which condenses from the ascending gas; owing to which arrangement the opening into each retort is effectually closed by a water-valve, and thus permits a fresh charge of coals to be thrown in, and of coke to be withdrawn in any one or more of the retorts, without interfering with the distillation going on in the others.

The aqueous portion of the liquid deposited in the hydraulic main, which is known as the _ammoniacal liquor_, and forms the principal source of the commercial salts of ammonia, consists principally of solution of carbonate of ammonium, but contains also sulphide, cyanide, and sulphocyanide of ammonium. After it leaves the hydraulic main, the gas passes into the _condenser_ (_e_), which is composed of a series of bent iron tubes (shown in the plate), these being kept cool either by the large surface they expose to the air, or, if necessary, by means of a stream of cold water applied to the outside.

Any of the volatile hydrocarbons or salts of ammonia escaping condensation in the hydraulic main are arrested in the condensers, but not always; hence it is necessary to afterwards carry the gas through a _scrubber_ (not figured in the plate) or case containing pieces of coke, over which a stream of water being made to trickle, absorbs any remaining ammoniacal vapours. The gas next passes through the _lime purifier_ (_f_), an iron box fitted with shelves, on which is placed slaked lime, which absorbs the carbonic acid, and part, but not the whole of, the sulphuretted hydrogen contained in the gas. Of the many methods devised for the removal of the sulphuretted hydrogen, none appears to be so successful and economical as that which consists in passing the gas over a mixture of sulphate of iron, slaked lime, and sawdust.

The gas, after it has become purified by the foregoing processes, is passed into the gasometer (_g_) (part of which is represented in the plate), whence it passes into the mains, by which it is conveyed to the various condensers. Another prejudicial impurity formed in gas is carbon disulphide, which when burned gives rise to small quantities of sulphuric acid, and this in time attacks certain kinds of furniture, as well as the bindings of books.

Dr Angus Smith effects the removal of the disulphide by passing the gas through a solution of plumbic oxide in caustic soda, diffused through sawdust.

The quality of coal-gas is largely dependent upon the temperature employed in its manufacture. If the retorts are insufficiently heated, the result will be the formation of certain easily-condensable hydrocarbons, which not only diminish the bulk of the gas, but cause considerable inconvenience by collecting in and blocking up the pipes. On the contrary, should too much heat be used, the gas becomes partially decomposed by contact with the red-hot retort, and deposits on its sides the substance known as "gas carbon," thus not only removing to a certain extent the constituent to which the gas owes its illuminating power, but impoverishing its lighting qualities still more, by diluting it with an unnecessary quantity of liberated hydrogen. These latter effects are forcibly illustrated in the following analysis of the gas collected from Wigan cannel coal at different periods of the distillation.

The best gas is said to be produced when the retorts are heated to a bright cherry red.

In 100 Volumes. 1st Hour. 5th Hour. 10th Hour.

Olefiant gas and volatile hydro-carbons 13·0 7·0 0·0
Marsh gas 82·5 56·0 20·0
Carbonic oxide 3·2 11·0 10·0
Hydrogen 0·0 21·3 60·0
Nitrogen 1·3 4·7 10·0

"The value of gas as an illuminating agent may be said to depend on the amount of hydrocarbons present, and on the relation which the carbon bears to the hydrogen in these substances. In marsh gas, CH_{4}, which is, practically speaking, non-luminous, the per-centage composition is, carbon 75, and hydrogen 25. In olefiant gas, C_{2}H_{4}, the carbon is 85·7, and the hydrogen 14·3, and the gas possesses a correspondingly greater amount of illuminating value. In acetylene, C_{2}H_{2}, we have a gas of still greater illuminating value, the proportion of carbon to hydrogen being also greater, the per-centage composition being, carbon 92·3, and hydrogen 7·7. In benzol, C_{6}H_{6}, we have the same per-centages; while in naphthalene, C_{10}H_{8}, a still higher ratio between the carbon and hydrogen exists, and a corresponding increased value in light-giving power. It was formerly taken as an axiom that the illuminating value of a mixture of gases was also proportionate to the relation between the carbon and hydrogen, but although this is very good as a rough criterion in practice, the statement must not be accepted as strictly true. The illuminating power of a mixture of gases is known now to depend far more on the nature of the particular compounds present, than upon the absolute proportion between the hydrogen and carbon; for while on the one hand it is possible to have a gas (marsh gas) containing as much as 75·4 per cent. of carbon, and yet which is valueless for illuminating purposes; it is also possible to have a mixture of gases in which the per-centage of carbon is far less, although the illuminating value is much greater."[326]

[Footnote 326: 'Chemistry, Theoretical, Practical, and Analytical,'--Mackenzie.]

Coal gas consists of a mixture of the following bodies:

Marsh gas (light carbonetted hydrogen).
Olefiant gas (heavy " " ).
Hydrogen.
Carbonic oxide.
Nitrogen.
Vapours of liquid hydro-carbons.
Vapour of bisulphide of carbon.

The yield of gas, and also the illuminating power of the product, vary greatly with different kinds of coal. The average yield may be roughly estimated at 10,000 cubic feet of gas per ton of coal.[327]

[Footnote 327: For practical details respecting the manufacture of this product, see the article COAL GAS in 'Ure's Dictionary of Arts, Manufactures, &c.,' 'Wagner's Chemical Technology,' and 'Chemistry, Theoretical, Practical, and Analytical.']

Anthracite is by no means suited for a gas coal. The best coals for this purpose are those which are bituminous; they comprise caking coal, parrot coal, and certain varieties of cannel coal. London gas (which is generally deficient in illuminating power) is manufactured principally from Durham and Newcastle coal.

In addition to the elementary composition of the coal, the amount and nature of the volatile matter contained in it is an important factor in its value as a source for gas. It should also yield a small amount of ash, and be as free as possible from sulphur, besides which its ultimate analysis should show a comparatively small proportion of oxygen. If there be an excess of this latter element, the production of the hydrocarbon illuminants will be diminished, since the hydrogen which would go to their formation would unite with the oxygen to form useless water.

The late Charles Mansfield proposed to increase the illuminating power of ordinary coal-gas, and to render water gas or even atmospheric air luminiferous, by passing them through sponges or over trays containing mineral naphtha or benzole; and a patent was taken out for this purpose. The gas so treated imbibes or dissolves a portion of the liquid, and burns with increased brilliancy. The method of saturating the gas with the liquid hydrocarbon is as follows:--"The apparatus consists of a brass reservoir or chamber attached to the end of the gas-pipe, near the burner. This reservoir may be in the shape of an oil-flask, made air-tight, with a screw-joint, or other means of supplying any highly volatile oil, turpentine, or mineral naphtha, and should be kept about half full. Into this reservoir the gas-pipe ascends a little above the surface of the oil; a very small jet-pipe of gas, regulated by a stop-cock, is branched off below this chamber, to supply a minute flame, so as to cause a sufficient evaporation from the oil to unite with the gas in the flask receiver. The whole is, of course, surmounted with the usual burner and lamp-glass."

The naphthalising of gas did not work well on a large scale. Recently, however, an attempt was made to get up a company in England to work a French patented process, which differed only from that of Mansfield's in the substitution of another hydrocarbon (probably a petroleum product) for benzol. The chemical and technical journals exposed this invention, and prevented the sinking of capital in a worthless undertaking. On a small scale, simple 'naphthalisers' appear to work very well.

The illuminating power of gas, as well as of other sources of light, may be directly ascertained by what is termed the 'comparison of shadows,' or indirectly, and more conveniently, by chemical analysis.[328] See AIR GAS, ILLUMINATION.

[Footnote 328: See 'Watts's Dictionary of Chemistry,' vol. i.]

=GASTROPHAN= (Apotheker J. Fürst, Prague). For strengthening the digestion and improving the appetite. Quassia, 30 grammes; orange berries, 15 grammes; galangal, 4 grammes; cardamoms, 2 grammes; star anise oil, 10 drops; orange-peel oil, 10 drops; spirit, 180 grammes; water, 120 grammes; digested and filtered. (Hager.)

=GASTROPHILE= (Dr Borchard). There are several numbers of this preparation. Soda water, containing common salt, perhaps in some of the numbers mixed with Glauber's salts.

=GAZ'OGENE.= [Fr.] _Syn._ AËRATING MACHINE. A portable apparatus for aërating water and other liquids. Many forms have been given to this instrument, but in all the principle is the same. Powders for generating carbonic acid gas are placed in a separate compartment, and the liquid to be aërated in another. The two compartments are connected by a suitable tube, and a second tube, furnished with a spring tap, affords an exit for the aërated liquid. By the aid of the gazogene, water, wine, ale, &c., may in a few minutes be fully saturated with carbonic acid gas, and so rendered brisk and piquant. By using fruit syrups, manufactured from English and foreign fruits, the most delicious aërated summer beverages can be made, resembling those so much esteemed by travellers in the South of Europe and the sea-board cities of the Western world.

The following are the proportions of soda and acid required for charging gazogenes:

For 2 pints, powdered tartaric acid, 280 grains; bicarbonate of soda, 340 grains.

For 3 pints, powdered tartaric acid, 340 grains; bicarbonate of soda, 420 grains.

For 5 pints, tartaric acid, 620 grains; carbonate of soda, 760 grains.

Put the acid and soda in different coloured papers.

=GEDACHTNISS-LIMONADE--Mnemonic Lemonade= (manufactured by G. M. Raufer, Vienna). A mixture of 15 parts phosphoric acid, 15 parts glycerin, 70 parts water. (Schädler.)

=GEHOR INSTRUMENT.= Instrument for deafness (Apotheker F. Brunner, Troppau). A little tube of silver plate, 2 centimètres long and as thick as a straw, with a small mussel-shaped widening at one end, which is wrapped in cotton wool, to be inserted in the ear.

=GEHOR LIQUOR=, Schweizer--Swiss Cure for Deafness (Raudnitz). Water mixed with a little coarse brandy. (Wittstein.)

=GEHOROL--Oil for Deafness= (C. Brockelmann, Soest). Provence oil adulterated with sunflower oil and mixed with very small traces of camphor and cajeput, sassafras, and rosemary oils. (Hager.)

=GEL'ATIN.= _Syn._ GELATINE; GÉLATINE, Fr.; GELATINA, L. Animal jelly, obtained by the prolonged action of boiling water on the organic tissue of the bones, tendons, and ligaments, the cellular tissue, the skin, and the serous membranes. Glue and size are coarse varieties of gelatin, prepared from hoofs, hides, skins, &c.; and isinglass is a purer kind, obtained from the air bladders of some other membranes of fish.

_Prop., &c._ Gelatin is insoluble in cold water, but dissolves with greater or less readiness on the application of heat, according to the source where it is obtained, and in this state forms a tremulous and transparent jelly on cooling; it is insoluble in both alcohol and ether, and is decomposed by the strong alkalies and acids; with tannic acid it forms an insoluble compound of a buff colour, which is the basis of leather; when acted on by cold concentrated sulphuric acid, it yields glycocoll or gelatin sugar; and when boiled with strong alkalies, it yields glycocoll and leucine. Chlorine passed into a solution of gelatin occasions a dense white precipitate (chlorite of gelatin), which ultimately forms a tough, elastic, pearly mass, somewhat resembling fibrin.

_Tests._ Its aqueous solution is recognised as follows:--1. It gelatinises on cooling. 2. It is precipitated by alcohol. 3. Bichloride of mercury gives a whitish flocculent precipitate. 4. Tannic acid or infusion of galls gives a copious yellowish-white, curdy precipitate, which, on being stirred, coheres into an elastic mass, insoluble in water, and incapable of putrefaction, and which, when dried, assumes the appearance of over-tanned leather. 5. The gelatinising property is destroyed by nitric acid. 6. It is not affected by either alum or acetate of lead. In this respect it differs from chondrin.

_Qual._ The goodness of commercial gelatin intended for food is readily proved by pouring boiling water over it, and digesting the two together for a short time. If it is pure and wholesome, its colour remains unaltered, and during its solution it continues entirely free from smell. The resulting solution and jelly are also odourless, neutral to test-paper, free from unpleasant taste, and perfectly transparent. If it forms a yellow gluey-looking mass, and evolves an offensive odour, it should be rejected as of inferior quality, and unfit for culinary purposes.

_Uses, &c._ Gelatin is largely employed as an article of food, as in soups, jellies, &c.; but its value in this respect has been, perhaps, overrated.[329] Animals fed exclusively on gelatin die of starvation. But when mixed with other food, especially with substances abounding in albumen, casein, or fibrin, gelatin may be useful as an aliment, and serve directly to nourish the gelatinous tissues. (Liebig.) Hence gelatin is a fitting substance to form part (but only a part) of the diet of convalescents, as it conveys nutrition directly to these tissues, without tasking the diminished powers of life for its conversion; but its use should be accompanied by a proper quantity of azotised animal food to supply the elements to the blood, for the support and increase of the muscular tissue, or fleshy portion of the body. In France gelatin obtained from bones is employed as a part of the diet in hospitals with the best effect, materially abridging the period of convalescence; but when given alone, all animals soon become disgusted with it, and die if not supplied with other food. (D'Arcet.) See GLUE, ISINGLASS, and _below_.

[Footnote 329: The reader interested in this subject should consult a paper by Carl Voit in the 'Zeitschrift für Biologie,' viii, 297-388.]

=Gelatin, Bone.= Obtained from crushed bones by boiling with water, or by the action of steam and water successively, either with or without pressure; or by maceration in dilute hydrochloric acid, to extract the phosphate of lime, the remaining gelatinous mass being well washed in cold water, and afterwards dissolved in boiling water in the usual manner. A little carbonate of soda is commonly added to the last water. Gelatin has even been extracted from fossil bones. "A soup was prepared from one of the bones of the great mastodon by the préfet of one of the departments of France." (Pereira.) Butchers' meat contains, on an average, 24% of dry flesh, 56% of water, and 20% of bone. The last will yield, by proper treatment, nearly 1-3rd of its weight of dry gelatin, or a quantity equal to about 6% of the meat from which it is cut. This, as well as other varieties of gelatin, is frequently blanched by sulphurous acid or animal charcoal, and tinged of various colours with the ordinary vegetable dyes. Thus, blue is given with sulphate of indigo or the juice of blue berries; green, with the juice of spinach; and red, with juice of red-beet.

=Gelatin, French.= _Syn._ CAKE GELATIN. Gelatin made up into small thin cakes, like the finer sorts of glue. A good deal of it is prepared in Paris from the cuttings of the skins used in making kid gloves and slippers.

=Gelatin, Patent.= Various qualities of gelatin are manufactured from glue pieces, or cuttings of the hides of beasts and skins of calves, and from inferior isinglass. According to Mr Nelson's specification, the crude materials, freed from hair, wool, flesh, and fat, after being thoroughly washed and 'scored,' are macerated for 10 days in a lye of caustic soda, and are then placed in covered vessels at a temperature varying from 60° to 70° Fahr., until they become tender; they are next washed to free them from alkali, and are then exposed to the vapour of burning sulphur until they acquire a sensibly acid reaction; they are now dissolved in water contained in earthen vessels heated to 150° Fahr., and the solution, after being strained, is put into 'settling vessels,' and heated to 100° to 120° Fahr., for 8 or 9 hours; at the end of this time the clear liquor is drawn off, and poured on the 'cooling slabs,' to the depth of about 1/2 an inch. As soon as the jelly is cold, it is cut into pieces, and washed in water until perfectly free from acid. It is then redissolved in water at about 85°, the solution poured out on slabs as before, and when cold, it is cut up, and, lastly, dried on nets.

According to another specification (Rattray's Patent) glue-pieces are steeped in water until they begin to putrefy, then washed with water, drained, and put from 12 to 24 hours into water strongly soured with sulphurous acid; they are afterwards washed first with cold water, and then in water at 120° Fahr., and are lastly converted into size by digestion for 24 hours in water at 120° Fahr., the resulting solution being filtered through bags of double woollen-cloth.

Patent gelatins are often sold cut up in imitation of 'picked isinglass,' to which, for the preparation of jellies, soups, and blancmanges, they are not much inferior.

=Gelatin, Rough.= _Syn._ GELATINE BRUT, Fr. From the skulls of oxen, the spongy insides of the horns and ribs, and from several other soft bony parts (deprived of fat), by washing them in water, digesting in an equal weight of hydrochloric acid of 6° Baume, in cold weather, and 4° or 5° in summer, for 10 days, then in acid of only 1° Baume for 24 hours longer; afterwards soaking and washing in successive portions of cold water until all the acid is washed out, adding an ounce of carbonate of soda to the last water. Used to make glue, &c. A similar article is prepared from the bones of sheep. The pieces, after being treated as above, are steeped in boiling water for a few minutes, wiped dry, and shaken together in a bag to remove the internal pellicle; after which they are cut into squares or dice to disguise them, and finally dipped into a hot solution of gelatin to varnish them. In this state the article is called 'GELATINE BRUT FIN,' Used to make soup. It keeps better than the cakes of portable soup. When less carefully prepared, it is also used to make glue for fine work. See BONE GELATIN.

=GELEE (pour le Goitre).= See LINIMENT OF IODIDE OF POTASSIUM.

=GELSEMIUM SEMPERVIRENS.= _Syn._ GELSEMIUM NITRIDUM, GELSEMIUM SEMPERVIRENS, GELSEMIUM LUCIDUM, ANONYMUS SEMPERVIRENS, BIGNONIA SEMPERVIRENS; LISANTHUS SEMPERVIRENS. The YELLOW JASMINE, or WOODBINE. The CAROLINA JASMINE.

Different botanists have placed the plant in different natural orders. De Candolle assigns it to the _Loganiaceæ_; Decaisne to the _Apocynaceæ_; Chapman to the _Rubiaceæ_.

The root, which is the only part of this plant employed in medicine, and of which a fluid extract has been introduced into the United States Pharmacop[oe]ia, as met with in English commerce occurs in two states; either in packets prepared by the shakers of New Lebanon, which contain the root in small pieces, formed into a compact mass by hydraulic pressure, and in which state it is difficult to powder; or it is simply sold cut up into pieces varying from two to eight inches in length, and one-third to three fourths of an inch in diameter. It is frequently mixed with about half its bulk of long, wiry, pale-brown rootlets.

The so-called gelsemium root consists chiefly of subterranean stem with a small proportion of true root, occasionally a slender piece of the aërial stem may be found intermixed, and is readily distinguished by its purplish colour and hollow centre, and by the silky and tow-like fibre, rendered visible when the epidermis is peeled off (fig. 1 _e_).

The true root is hard and woody, slightly undulated in outline, very sparingly branched, except in the slender pieces, externally of a pale brown colour, nearly smooth, and furnished with a thin scurfy cuticle, which is slightly cracked longitudinally. When a transverse section is examined with a lens, the bark of the root is seen to be very thin, and to consist of two layers, the inner one being usually almost as pale as the woody portion, and of somewhat soft texture, the outer one is darker and more compact (fig. 1 _b_, _c_).

The meditullium, or woody portion of the root occupies nearly its whole diameter, is of a pale yellowish bright colour, the yellow tint becoming much more distinct when the root is wetted. The medullary rays are white and very distinct, and the woody tissue between the rays is very porous, the pores being very small, but visible to the unaided eye, especially when the root is broken instead of cut (fig. 1 _d_). There is no pith or central cavity in the root. The root has a bitter taste and pleasant flavour, somewhat between those of senega and green tea; this is more readily perceived in the tincture.

The subterranean stem (fig. 1 _a_) is also furnished with rootlets, but is easily distinguished from the root by the presence of a small, dark coloured, central cavity representing the pith, and by the external surface being rougher, and frequently variegated with dark longitudinal lines, which are the remains of the same purplish cuticle which presents so marked a feature in the aërial stem. The bark is thicker than that of the true root, and the inner layer is usually dark brown. If the subterranean stem is broken slowly and carefully, a thin row of silky fibres projects fully a quarter of an inch from the broken edge. The fibres do not appear when the bark of the root is broken, and thus serve to distinguish the stem of this drug from the root. Experiments as to the relative value of the bark of the root and stem are wanting. The bark of the stem has the same bitter taste as that of the root, and if it be hereafter shown that it is equally active, the above character of scattered strong fibres, taken in conjunction with the flavour of the drug and its porous structure, will serve to distinguish it from all other roots and stems used in materia medica.[330]

[Footnote 330: Holmes.]

_Medicinal properties._--The American medical journals record the successful administration of gelsemium in a great number and variety of diseases, including intermittent, remittent, typhoid, and yellow fevers, the irritative fevers of childhood, inflammation of the lungs and pleura, dysentery, rheumatism, and other inflammatory affections, neuralgia, obstinate menstruation, delirium tremens, morbid wakefulness, St. Vitus' dance, hysteria, epilepsy, spasmodic stricture of the urethra, and gonorrh[oe]a. Dr Hurd, an American physician, reports very favorably of the drug as a cardiac sedative, and considers it more efficient than any other remedy in the palpitation and the difficult breathing that accompany heart disease; and Dr Hill, of Maine, finds it when combined with bromide of potassium useful in irritable bladder.

Its principal use, however, in American medical practice has been as a febrifuge. In periodic fevers it has been employed with great advantage, as well as in cases of intermittent fever, which having failed to yield to quinine alone, succumbed, when this latter medicine was combined with gelsemium.

In England gelsemium has been successfully employed for the relief of facial neuralgia, or of the pain caused in the face and jaws by decayed teeth; as well as in obscure nervous affections and severe headaches. It is given principally in the form of tincture; but sometimes in powder in doses of from one to two grains.

The therapeutic action of gelsemium is believed to be due to the sedative effect it exercises on the nervous and arterial systems--hence its power in controlling the nervous irritability so prevalent during fever. In moderate doses it causes a sensation of agreeable langour, accompanied with muscular relaxation; in larger doses, dizziness, dilated pupil, double vision, general muscular debility and prostration; these symptoms being accompanied by a diminution in the force and frequency of the pulse as well as in the respiration. At the same time the patient becomes insensible to pain; but is free from stupor and delirium. These symptoms are said to pass off, after a time, and to be attended with no unpleasant results.

The 'Lancet' as well as many of the American medical journals record several cases of poisoning arising from giving an overdose of this drug. The symptoms are a great prostration of nervous energy, accompanied by paralysis of sensation and motion. When death occurs it is probably owing to syncope. The antidotes are, first, an emetic, and after this has acted, stimulants, such as carbonate of ammonia with brandy, or aromatic spirits of ammonia. In cases accompanied with insensibility, recourse should be had to electricity.

Kollock, in the 'American Journal of Pharmacy' for 1855, states that he found the root on analysis to yield volatile oil, dry acrid resin, fatty resin, fixed oil, gallic acid, starch, pectic acid, albumen, extractive matter, lignin, gum, a yellow colouring matter, mineral matter (chiefly salts of potassium, calcium, magnesium, iron and silica), and an alkaloid, to which the name gelseminine or gelsemia has been given. Kollock also states that the leaves and flowers contain the same ingredients as the root, although in much smaller quantities.

Eberle, in the 'American Journal of Pharmacy' for 1864, says he failed to obtain gelseminine from the root. In a paper contributed to the 'American Journal of Pharmacy,' for January, 1870, by Dr Wormley, the author stated that he said he not only succeeded in obtaining pure gelseminine from the root, but also a peculiar acid which he calls gelseminic, or gelsemic[331] acid; which he regards as existing in combination with the gelsemia, forming the gelsemate of gelsemia.

[Footnote 331: Professor Sonneschien, having submitted the so-called _Gelseminic Acid_ to analysis thinks there can be no doubt that it is perfectly identical with æsculin, a glucoside obtained from the bark of the horse-chesnut--the _Esculus hippocastanum_.]

Probably the alkaloid gelseminine may at some future time be introduced into medicine, since it would appear to be the chief ingredient to which the root owes its activity. It is strongly poisonous. Dr Wormley injected one eighth of a grain under the skin of a large cat, which in 40 minutes exhibited great prostration, and died in an hour and a half from the time of the injection of the poison. The properties of the gelseminic acid, the resin, the volatile oil, and other ingredients of the root, have not been fully investigated. See TINCTURE OF GELSEMIUM, GELSEMININE.

In the 'American Journal of Pharmacy' for April, 1877, Dr Wormley gives the following directions for the preparations of gelseminic acid, and gelsemine:--A given volume of fluid extract, acidulated with acetic acid, is slowly added with constant stirring to about eight volumes of water; after the separated resinous matter has completely deposited, the liquid is filtered, and the filtrate concentrated on a water bath, to something less than the volume of fluid extract employed. The gelseminic acid is then extracted from the concentrated fluid by ether, after which the liquid is treated with slight excess of carbonate of sodium, and the gelsemine extracted with ether or chloroform. For the extraction of the first of these principles, it is not essential that the liquid should be acidulated, but in the presence of a free acid the results are more satisfactory.

=GEMS=. _Syn_. JEWELS; GEMMÆ, L. "Gems are precious stones, which, by their colour, limpidity, lustre, brilliant polish, purity, and rarity, are sought after as objects of dress and decoration. They form the principal part of the crown jewels of kings, not only from their beauty, but because they are supposed to comprise the greatest value in the smallest bulk; for a diamond, no larger than a nut, or an acorn, may be the representative sign of the territorial value of a whole country, the equivalent in commercial exchange for a hundred fortunes, acquired by severe toils and privations." "Among these beautiful minerals mankind have agreed in forming a select class, to which the title of gems or jewels has been appropriated; while the term precious stone is more particularly given to substances which often occur under a more considerable volume than fine stones ever do. Diamonds, sapphires, emeralds, rubies, topazes, hyacinths, and chrysoberyls, are reckoned the most valuable gems;--crystalline quartz, pellucid, opalescent, or of various hues, amethyst, lapis lazuli, malachite, jasper, agate, &c., are ranked in the much more numerous and inferior class of ornamental stones." (Ure.)

_Tests._ The only tests applicable to gems and precious stones are the determination of their relative hardness and their specific gravity. By the first test, pastes or factitious gems are readily detected; but beyond this, owing to the difficulty of applying it, it ceases to be useful to persons unconnected with the trade. The determination of the specific gravity is, however, of more general application, as gems are generally dismounted when offered for sale, or are so set that they may be removed from their 'mountings' without injury or inconvenience. See SPECIFIC GRAVITY, and _below_.

_Obs._ The relative hardness of the different substances is measured by the power they possess of cutting or scratching the other substances having a smaller number attached to them in the table. Thus, no gem but the DIAMOND (20) will scratch either the RUBY (17) or the SAPPHIRE (16); and, for the same reason, a blue stone that will cut the EMERALD or the TOPAZ can be no other than the SAPPHIRE. The sp. gr. is ascertained in the usual manner, and will be found sufficiently indicative of the true nature of the stone when considered in connection with its other characteristics. The index of refraction is a certain key to the quality of the stone, in the hands of those who are capable of determining it, and may be applied to either mounted or unmounted gems. The most convenient instrument for the purpose is Wollaston's 'REFLECTING-GONIOMETER,'

=Gems, Facti''tious.= These, with few exceptions, are made of very pure, fusible, highly transparent, and dense glass, usually termed 'PASTE' or 'STRASS,' which is generally formed of oxide of lead, potassa, and silica, with small quantities of other ingredients to increase the brilliancy and clearness. The characteristic tints are imparted by the addition of metallic oxides. The beauty of artificial stones and gems depends, chiefly, upon the tint of the real stones being exactly imitated, and upon proper care and skill being exercised in the cutting, polishing, and mounting them. All the coloured glasses, and enamels, may be worked up into artificial gems.

TABLE _of the Hardness, Specific Gravity, and
Refractive Power of the principal_ GEMS _and_ PRECIOUS
STONES, _and some other_ MINERALS; _compiled expressly
for this work_.

----------------------------------------------------------------------------------
| Name. | Relative | Specific Gravity. | Index of Reflection. |
| | Hardness. | | |
---------------------------------------------------------------------------------|
| Agate | 12 | 2·6 | |
| Amethyst (occidental) | 11 | 2·7 | |
| Calcareous spar | 6 | 2·7 | |
| Chalk | 3 | 2·7 | |
| Chrysolite | 10 | 3·7 | |
| Cornelian | 11 | 2·7 | |
| Crystal | 11 | 2·6 | |
| Diamond (bluish) | 19 | 3·3 | } |
| " (cubic) | 18 | 3·2 | } |
| " (from Ormus) | 20 | 3·7 | } 2·439 |
| " (pink) | 19 | 3·4 | } |
| " (yellowish) | 19 | 3·3 | } |
| " (average colourless)| 19 to 20 | 3·3 to 3·55 | } |
| Emerald | 12 | 2·8 | |
| Fluor spar | 7 | 3·5 | 1·434 |
| Garnet | 12 | 4·4 | 1·815 |
| Glass | { } | 2·3 to 3·62 | 1·525 to 2·028 |
| " (crystal or flint) | {various} | 3·0 " 3·6 | 1·830 " 2·028 |
| " (plate) | { } | 2·5 " 2·6 | 1·514 " 1·542 |
| Gypsum | 5 | 2·3 | |
| Jasper (green) | 11 | 2·7 | |
| " (reddish yellow) | 9 | 2·6 | |
| Onyx | 12 | 2·6 | |
| Opal | 10 | 2·6 | |
| Quartz | 10 | 2·7 | 1·548 |
| Ruby | 17 | 4·2 | } 1·779 |
| " (pale, from Brazil) | 17 | 3·5 | } |
| " (spinelle) | 13 | 3·4 | 1·764 |
| Sapphire (deep blue) | 16 | 3·8 | } 1·794 |
| " (paler) | 17 | 3·8 | } |
| Sardonyx | 12 | 2·6 | |
| Schoerl | 10 | 3·6 | |
| Topaz | 15 | 4·2 | |
| " (Bohemian) | 11 | 2·8 | |
| " (whitish) | 14 | 3·5 | |
| Tourmaline | 10 | 3·0 | |
| Zeolite | 8 | 2·1 | |
| Zircon | -- | -- | 1·961 |
----------------------------------------------------------------------------------

MM. Fremy and Feil have lately succeeded in manufacturing artificial corundum, ruby and topaz, having a composition the same as the natural stones. The process by which they have effected this consists in fusing together at a red heat, in the furnace of a glass works for a considerable time, a fusible aluminate (such as aluminate of lead), and some silicious body.

The silica is found to unite with the lead, and to liberate the alumina in the crystalline form. When equal weights of alumina and red lead are heated together in a crucible made of some refractory silicious substance, the above conditions if the temperature has been maintained sufficiently long and high ensue, and there is found in the crucible at the end of the operation a layer of silicate of lead, and very frequently another of pure crystallised alumina or corundum.

The ruby colour is given by adding to the mixture in the crucible two or three per-cent. of bichromate of potash, the blue being produced by the addition of a small quantity of oxide of cobalt, with a trace only of bichromate of potash. A film of silicate of lead very frequently adheres to the ruby crystals, and this has to be removed.

In some instances, however, the crystals occur nearly pure, and are precisely similar to the natural gems in crystalline form, composition, hardness, and lustre.

Upon being heated, the artificial ruby, like the natural one, loses its rose colour, and recovers it again on cooling. It is said that the factitious gems hitherto obtained are not, as a rule, equal in lustre to the natural ones, and are consequently not so well suited for jewellers' work; also that they do not present to the lapidary conditions favorable to cleavage or cutting. They are, however, very well adapted for the works of watches. See ENAMELS, PASTES, &c.

=GENE'VA.= See GIN and HOLLANDS.

=GEN'TIAN ROOT.= _Syn._ GENTINÆ RADIX, L. The dried root of _Gentiana lutea_, or 'yellow gentian.' _Dose_, 10 to 30 gr.; as a simple bitter tonic, and stomachic, in dyspepsia, loss of appetite, gout, &c. It was formerly a favourite remedy in agues. "Joined with galls or tormentil, and given in sufficient quantity, it has not failed in any intermittents in which I have tried it." (Dr Cullen.) In excessive doses it is apt to relax the bowels and disturb the system. When taken for some time, it imparts its bitter flavour to the perspiration and urine. See DECOCTION, EXTRACT, &c.

=GEN'TIANIN.= _Syn._ GENTIANINE; GENTIANINA, L. A substance obtained by MM. Henry and Caventou from the root of common gentian.

_Prep._ 1. Gentian root (in powder) is digested for 2 or 3 days in cold ether, with agitation, and the filtered tincture evaporated to dryness; the residuum is dissolved in rectified spirit, and the solution is again evaporated; the semi-crystalline mass is, lastly, redissolved in either alcohol or ether, and crystallised by careful evaporation.

2. (Magendie.) The ethereal extract is exhausted with cold alcohol (rectified spirit), as before, and the resulting tincture is evaporated to dryness; the residuum is dissolved in water, calcined magnesia added in excess, and the whole boiled and filtered; the sediment is digested in ether, and the ethereal tincture allowed to crystallise by slow evaporation.

_Prop., &c._ Gentianin forms golden-yellow needles, scarcely soluble in cold water, but very soluble in alcohol and ether. It is a powerful bitter and stomachic.--_Dose_, 1/2 gr. to 2 gr.

=GER'MAN PASTE.= _Prep._ From pea-meal, 2 lbs.; sweet almonds (blanched), 1 lb.; fresh butter or lard, 1/4 lb.; moist sugar, 5 oz.; hay saffron, 1/2 dr.; beat to a smooth paste, adding cold water q. s., granulate the mass by passing it through a colander, and expose the product to the air in a warm place, until quite hard and dry. The addition of 2 or 3 eggs improves it. Used to feed larks, nightingales, and other insectivorous birds. It will keep good for 12 months in a dry place.

=GER'MAN SILVER.= _Syn._ ALBATA, ARGENTAN, _Electrum_, NICKEL SILVER, TUTENAG, VIRGINIAN PLATE, WHITE COPPER. A well-known alloy, the finer varieties of which nearly equal silver in whiteness and susceptibility of receiving a high polish, whilst they surpass it in hardness and durability. The following formulæ are from the highest authorities, or are the results of actual analysis of the finest commercial samples:--

_Prep._ 1. Copper, 50 parts; nickel, 20 parts; zinc, 30 parts. Very malleable, and takes a high polish.

2. Copper, 50 parts; nickel, 26 parts; zinc, 24 parts. Closely resembles silver; an excellent sample.

3. Copper and zinc, of each 41 parts; nickel, 18 parts. Rather brittle.

4. (M. Gersdorff.) Copper, 50 parts; nickel and zinc, of each 25 parts. Very white and malleable, and takes a high polish. Recommended as a general substitute for silver.

5. (Gersdorff.) Copper, 60 parts; nickel and zinc, of each 20 parts. For castings, as bells, candlesticks, &c.

6. (Gersdorff.) Copper, 60 parts; nickel, 25 parts; zinc, 20 parts. For rolling and wire. Very tough and malleable.

7. (Sample made from the ore of Hilburghausen.) Copper, 40-1/2 parts; nickel, 31-1/2 parts; iron, 2-1/2 parts; zinc, 25-1/2 parts. Equal to the best Chinese sample.

8. (Pelouze.) Copper and nickel, equal parts. Recommended by M. Pelouze as superior to any of the alloys containing zinc.

9. (Pelouze.) Copper, 2 parts; nickel, 1 part. Not so white as the last, but more malleable.

10. (White Copper from China.)--_a._ Copper, 30 parts; nickel, 36 parts; zinc, 34 parts.

_b._ (Said to be prepared from native ore.) Copper, 41 parts; nickel, 32 parts; iron, 2-1/2 parts; zinc, 24-1/2 parts. Silvery white, takes a high polish, very sonorous, malleable both cold and at a dull-red heat, and may be rolled into leaves or formed into wire.

11. (White metal spoon, sold as 'German Plate.') Copper, 55 parts; nickel, 24 parts; zinc, 16 parts; tin, 3 parts; iron, 2 parts.

_Anal._ This may be briefly described as follows:--_a._ 100 gr. of the alloy is digested in nitric acid q. s., diluted with a little water. If the sample is unequally attacked by the acid, and a white external shell is observed which dissolves more slowly than the internal portion, it is 'plated' on those parts with silver. If this silver shell or casing has a polished surface on both sides, the article has been 'electro-plated,' if the contrary is the case, it has most probably been plated in the usual way.

_b._ The solution being completed, heat is applied to expel the excess of acid, and the remainder is largely diluted with distilled water; dilute hydrochloric acid is now dropped in as long as it occasions a precipitate, and the whole, after being moderately heated for a short time, and cooled, is thrown upon a small paper filter; the precipitate on the filter is next washed with distilled water, carefully dried, and ignited in a small porcelain crucible, the filter itself being separately burnt on the cover of the crucible, and the ashes added to its contents prior to ignition. Every 143-1/2 gr. of the resulting fused chloride is equal to 108 gr. of metallic silver.

_c._ The filtered liquid (see _b_) is next treated with a stream of sulphuretted hydrogen, and the black precipitate is collected, washed, and digested in strong nitric acid; when the solution is complete sulphuric acid is dropped in to precipitate the lead (if any is present); if a precipitate is formed, the whole is evaporated to dryness, and the excess of sulphuric acid expelled by a rather strong heat applied towards the end; the dry mass is now collected on a filter, washed with a mixture of water and alcohol, dried, and exposed to slight ignition in a porcelain crucible. Every 152 gr. of the resulting dry sulphate is equal to 104 gr. of lead.

_d._ The liquor filtered from the sulphate of lead, or (in its absence) the nitric solution of the precipitate produced by the sulphuretted hydrogen (see _c_), is next treated with potassa, &c., as described under the analysis of brass. Every 40 gr. of the dry protoxide thus obtained represents 32 gr. of pure copper.

_e._ The liquor which was filtered from the precipitate produced by the sulphuretted hydrogen (see _c_) is boiled until it loses its offensive odour, and is then precipitated with carbonate of soda, in slight excess, and again boiled for a few minutes; the precipitate (mixed oxides of nickel and zinc) is collected, washed, and redissolved in dilute acetic or nitric acid, in excess; a current of sulphuretted hydrogen is next passed through the solution, the precipitate collected on a filter, washed, redissolved in hydrochloric acid, and the solution again treated with carbonate of soda; the last precipitate (oxide of zinc) is washed, dried, and gently ignited. Every 40 gr. of this oxide is equivalent to 32 gr. of metallic zinc.

_f._ The washings of the precipitated oxides and the liquid filtered from the precipitate occasioned by the sulphuretted hydrogen (see _e_) are mixed together, pure solution of ammonia added in considerable excess, and the mixture agitated for some time; the undissolved portion of the precipitate is then collected on a filter, washed with distilled water, redissolved in dilute nitric acid, again precipitated with solution of potassa, and this last precipitate (ferric oxide) washed, dried, ignited, and weighed. Every 80 gr. represents 50 gr. of metallic iron.