Chapter M: F. Capitaine, who, acting upon a suggestion made by Liebig, some twenty (1)

years since, has recently taken up the subject of the manufacture of soluble glass, and silicate of potash, from _farine fossile_ (an infusorial earth), has published an account of his researches in 'Dingler's Polytechnic Journal.'[334]

[Footnote 334: See 'The Journal of the Society of Arts' for January 11th, 1878.]

Although M. Capitaine does not think that the farine will be able to compete in cheapness with flint (where this latter is abundant) for the preparation of the alkaline silicates, he states that it possesses the advantage over flint of being much more soluble, and of yielding a far more neutral glass; added to which the production of the silicate is said to be effected with much less trouble than when flint is employed. An important condition is, that the farine must be first well calcined, since if the least trace of organic matter be left in it, the resulting solution will have a yellowish or brownish tint, which will make it unsaleable.

"The lyes being prepared partly with caustic soda, and partly with carbonate of soda, had densities ranging from 1·22 to 1·24 which were found to be most advantageous. A reservoir furnished with mechanical agitators, was about two thirds filled with lye, and the necessary quantity of calcined farine added, the stirring being kept up continually. The proportion of farine is easily calculated on the datum, that one part of hydrate of soda dissolves about 2·8 parts of chemically pure farine, the quality of which varies but little. Lye of the density indicated produces a rather light solution, which presents little resistance to the agitators. If steam is afterwards introduced the solution becomes very rapid, when the pressure reaches about three atmospheres, and at the end of about three hours the silica is completely dissolved.

"For the preparation of silicate of potash for surgical purposes the farine fossile is said to be peculiarly adapted. In this case the boiling must be continued for one or two hours longer than in the case of soluble glass, with an addition of 10 to 15 per cent. of farine."

_Uses. &c._ Soluble glass, in solution, has been used to render textile fabrics less combustible, as a varnish to protect stone, and as a vehicle in fresco-painting, The soda compound (silicate of sodium) is largely used as a dung-substitute in calico-printing, and by soap manufacturers in place of the resinates formerly in use. 10 or 12 tons are produced weekly in the district of South Lancashire. The potassa compound (silicate of potassium) has been recommended as a remedy for gouty concretions by Mr Ure.--_Dose_, 10 to 15 gr., in 6 or 8 fl. oz. of water twice a day. See DUNGING, VARNISH, &c.

=Glass, Toughened.= _Syn._ VERRE TREMPÉ. M. de la Bastie's process for converting ordinary, into toughened, tempered, or hardened glass, may in general terms be said to consist in heating the glass to a certain temperature, and then plunging it into an oleaginous bath. For the process, however, to be successful, the observance of a number of minute details is essential; if these be neglected failure is certain to ensue. Thus it is found, that if the glass be insufficiently heated it will, when immersed in the bath, fail to be affected by it, and will consequently experience no alteration in properties. Again, if overheated, it will then get out of shape; or, further it may be heated to the right temperature, and yet be spoilt as it is being transferred to the bath. Moreover, the exact composition of the bath itself, and its temperature constitute very important conditions, the most trifling departure from which may give rise to unsatisfactory results. All these obstacles appear to have been overcome by M. de la Bastie, who has designed plant in the shape of furnaces and baths, by means of which the tempering process can be carried out, without chance of failure. When the glass is brought to the required temperature, all that is necessary is that they should be plunged into the bath, and instantly withdrawn. The cost of the operation is stated to be very small.

"The process as carried out at New York is thus described:--The glass after being run from the furnaces and moulded as usual, instead of being put into annealing pans, is immersed in a hot bath consisting of three parts of flaxseed oil, and one part of tallow. The bath stands at about 320°; and after remaining in this the ware is removed to a second, and similar bath, by which it is cooled down to about 200°. Finally the pieces are immersed in a water bath, and then dipped into a quantity of ordinary refined burning oil. They are then cleaned, ready for packing, with plaster of Paris powder. The work is but in its infancy, and but one small furnace is used in the experiments. Improvements will doubtless be made, by which the cleaning can be done more rapidly than by the powdered plaster, probably some chemical being used for the purpose. It is supposed that the oil works into the pores of the hot glass, and thus toughens it. Great care has to be exercised in the final cooling by water, as too long a contact with the air in changing from one bath to another, makes the ware crack. Articles cooled entirely in oil retain the oil on the surface, but are thus rendered stronger than otherwise.

This new process is very much employed in the manufacture of lamp chimneys, though they have the disadvantage of flying into small pieces, and with violence when they do break, which sometimes does occur."[335]

[Footnote 335: Supplement to 'Ure's Dictionary of Arts, Manufactures, &c., 1878.]

The results so far obtained when glass is subjected to M. de la Bastie's process are variable. In some cases the articles subjected to it possess great toughness, and the glass bears a blow without experiencing any fracture. In other instances, however, a slight fall or blow shivers it to atoms. When the toughened glass under any circumstances breaks, it possesses a disadvantage over ordinary broken glass, in distributing itself into a great number of small, sharply angular fragments.

Another process for toughening glass, which has been patented by Herr F. Siemens, consists in heating, and then pressing, and suddenly cooling the glass to be hardened; but when the articles are such as are usually moulded, the hardening and tempering are accomplished at the same time as the pressing; thus the molten glass is run into suitable moulds, and while still highly heated, is squeezed, the moulds effecting the necessary cooling, a proceeding which renders the employment of the oleaginous bath unnecessary. Mr Bauer's method for toughening glass consists in heating ordinary glass plates so strongly that they begin to bend from softening, and then plunging them into a liquid paraffin bath having a temperature of 200°.

Toughened glass is liable to rupture under circumstances that have not yet been accounted for.

M. de la Bastie conceives that the fragile nature of glass is due to the weakness of the cohesion of its particles, and that if this cohesive power can be increased, the strength of the material will be improved in proportion. M. de la Bastie first tried to obtain this end by forcibly compressing the glass while in a plastic or fluid condition, but without success; and it was only after various experiments that he was enabled to harden the glass, by dipping it into oil or any other liquid that permitted of being heated to a temperature considerably above that of water.

=GLAZE.= _Syn._ GLAZING. Any coating or varnish applied to a surface to render it smooth and glassy; any factitious, shining exterior. The following applications of this term are the following:--

=Glaze.= In _cookery_, is commonly understood to be gravy or clarified soups boiled until it gelatinises on cooling. It is used as a species of varnish to cover various dishes for the table, and may be spiced and flavoured according to the fancy of the cook. White of egg is generally used as a glaze for pastry.

=Glaze.= In the _porcelain_ and _earthenware manufacture_, the vitreous coating which is so essential to the beauty and utility of potter's ware. Glazes are either white or coloured. The former, by the addition of the colouring ingredients used for enamels, are converted into the latter.

_a._ For EARTHENWARE:--

_Prep._ 1. (With lead.) White lead (pure), 53 parts; quartz or ground flints, 36 parts; Cornish stone, or felspar, 16 parts; white flint glass, 5 parts; reduce the whole to an impalpable powder. For common earthenware.

2. (Without lead.) Fine washed sand, 10 parts; purified potash, 8 parts; nitre, 1 part; slaked lime, 2 parts; nitre, 4-3/4%; powder, mix, heat the mixture in a blacklead crucible in a reverberatory furnace, till the mass flows into a clear glass; let this cool, then reduce it to fine powder. For glazing pharmaceutical and chemical vessels.

_b._ For PORCELAIN:--

_Prep._ (Rose.) Felspar, 27 parts; borax, 18 parts; finest siliceous sand, 4 parts; nitre, soda, and purest china clay (Cornish), 3 parts; mix, heat to a 'frit,'[336] powder, and add of calcined borax, 3 parts.

[Footnote 336: A technical term for the half-fused mass formed by heating together the materials of which glass is composed.]

_c._ For STONEWARE:--

1. (Ure.) White felspar, 26 parts; soda, 6 parts; nitre, 2 parts; borax, 1 part; 'frit' together as last. Of the product take 13 parts; red lead, 50 parts; white lead, 40 parts; flints, 12 parts; reduce the whole to powder as before. For painted stoneware.

2. From common salt, which is thrown into the heated furnace containing the ware. It is volatilised and decomposed by the joint agency of the silica of the ware and of the vapour of water always present; hydrochloric acid and soda are produced, the latter forming a silicate, which fuses over the surface of the ware, and gives a thin but excellent glaze. 'SALT-GLAZED STONEWARE' is now generally used for large chemical vessels, drain-pipes, &c.

_Obs._ Glazes must be reduced to very fine powder. For use, they are ground with water to a very thin paste or smooth cream, into which the articles, previously baked to the state called 'biscuit,' are then dipped; they are afterwards exposed to a sufficient heat in the kiln to fuse the glaze. Another method of applying them is to immerse the biscuit in water for a minute or so, and then to sprinkle the dry powder over the moistened surface.

=GLI'ADIN.= _Syn._ GLUTIN, VEGETABLE GELATIN. One of the proximate principles of wheat gluten, soluble in alcohol.

=GLIADINPFLASTER= (A. L. Klose, Berlin). For rheumatism. A thin paper on which is spread a solution of gelatin containing spirit and some acrid substance, such as cantharides or euphorbium.--_Hager._

=GLOB'ULIN.= _Syn._ CRYSTALLIN. An albumenoid body existing in the crystalline lens of the eye.

=GLOVE POW'DER.= _Prep._ 1. From Castile soap, dried by exposure to a warm dry atmosphere for a few days, and then reduced to fine powder in a mortar. Used to clean gloves.

2. Pipe-clay, coloured with yellow ochre, umber, or Irish slate q. s., and afterwards scented with a little powdered orris root or cloves. Used to colour gloves made of doe-skin and similar leather.

=GLOVES.= _Syn._ GANTS, Fr. Although gloves constitute a less costly article of dress at the present day than they did during the Middle Ages, the following information may nevertheless be sometimes found of value to their wearers:--

GLOVE CLEANING. 1. (KID GLOVES.)--_a._ Damp them slightly, stretch them gently over a wooden hand of appropriate size, and clean them with a sponge dipped in benzol, recently rectified oil of turpentine, or camphine; as soon as they are dry, withdraw them gently from the stretcher, and suspend them in a current of air for a few days, or until they cease to smell of the cleaning liquid used. The smell of benzol passes off very quickly. Heat must be avoided. The cleaning liquid should be used liberally, and the first dirty portion should be sponged off with clean liquid.

_b._ By employing a saponaceous compound. See GANTEINE.

2. (DOE-SKIN and WASH-LEATHER GLOVES.)--_a._ Stretch them on a hand, or lay them flat on a table, and rub into them a mixture of finely powdered fuller's earth and alum; sweep it off with a brush, sprinkle them with a mixture of dry bran and whiting, and, lastly, dust them well off. This will not do if they are very dirty.

_b._ Wash them in lukewarm soft water, with a little Castile or curd soap, ox-gall, or bran tea; then stretch them on wooden hands, or pull them into shape without wringing them; next rub them with pipe-clay and yellow ochre, or umber, or a mixture of them in any required shade made into a paste with ale or beer; let them dry gradually, and, when about half dry, rub them well, so as to smooth them and put them into shape; when they are dry, brush out the superfluous colour, cover them with paper, and smooth them with a warm (not hot) iron.

GLOVE DYEING. LEATHER GLOVES, if not greasy, may be dyed with any of the ordinary dyes by brushing the latter over the gloves stretched out smooth. The surface alone should be wetted, and a second or third coat may be given after the former one has become dry. When the last coat has become thoroughly dry, the superfluous colour should be well rubbed out, a smooth surface given them by rubbing them with a polished stick or piece of ivory, and the whole gone over with a sponge dipped in white of egg.

=Gloves, Cosmetic.= _Syn._ GANTS COSMETIQUES. These are mock kid or lambskin gloves rubbed over, on the inside, with the following composition:--Spermaceti cerate, 3 oz.; melt, add of balsam of Peru, 1/2 dr., stir for 5 minutes, and, after a few minutes' repose, pour off the clear portion; to this add of oil of nutmeg, 15 drops; oil of cassia and essence of ambergris, of each 6 drops; and stir until cold. Used by ladies to soften the hands and to prevent or cure chilblains and chaps. They are commonly worn all night in bed.

=GLUCI'NUM.= Gl. _Syn._ BERYL'LIUM. The metallic base of glucina. It was first obtained by Wöhler, in 1828, by a similar process to that adopted for aluminum, a metal which it greatly resembles. See ALUMINUM.

=Gluci'num, Oxide of.= _Syn._ GLUCINA, BERYLLIA. A pulverent white substance, found as silicate in the beryl, emerald, &c.

_Prep._ The beryl, in fine powder, 1 part; carbonate of potassium, 3 parts; expose the mixture to a strong red heat for half an hour, dissolve the calcined mass in hydrochloric acid, and evaporate the solution to dryness; redissolve the residuum in very dilute hydrochloric acid, and precipitate with pure ammonia; wash the precipitate well, digest it with a large quantity of carbonate of ammonium, filter, and boil the solution as long as carbonate of glucinum subsides. By exposure to a red heat the carbonic acid may be expelled, and the earth rendered anhydrous.

_Prop., &c._ Glucina closely resembles alumina, from which, however, it is distinguished by its solubility when freshly precipitated in a cold solution of carbonate of ammonia, from which it is again thrown by boiling. Glucina is classed with the earths. The beryl contains 14% of this substance.

=GLU'COSE.= See SUGAR (Grape).

=GLUE.= _Syn._ GLUTEN, GLUTINUM, L.; COLLE, COLLE FORTE, Fr. Inspissated animal jelly, or gelatin, used as a cement.

_Prep._ Glue is principally prepared from the parings and waste-pieces of hides and skins, the refuse of tanneries, and the tendons and other offal of slaughter-houses. These substances, when intended for the glue-maker, are steeped for 14 or 15 days in milk of lime, then drained, and dried by exposure to the air. This constitutes what is termed the 'cleansing' or 'preparation,' and in this state the 'glue pieces,' as they are called, may be kept for a long time, and transported to any distance without suffering decomposition. Before conversion into glue, they are usually again steeped in weak milk of lime, and next well washed and exposed to the air for 24 to 30 hours. They are then placed in a copper boiler two thirds filled with water, and furnished with a perforated false bottom, to prevent them from burning, and as much is piled on as will fill the vessel and rest on the top of it. Heat is next applied, and the whole gently boiled or simmered together, until the liquor on cooling forms a firm gelatinous mass. The clear portion is then run off into another vessel, and a very small quantity of alum (dissolved) added; here it is kept hot by a water bath, and allowed to repose for some hours to deposit its impurities, after which it is run into the 'congealing boxes,' and placed in a cool situation. The next morning the cold gelatinous masses are turned out upon boards wetted with water, and are cut horizontally into thin cakes with a stretched piece of brass wire, and then into smaller cakes with a moistened flat knife. The latter are placed on nettings to dry. The dry cakes of glue are next dipped one by one into hot water, and slightly rubbed with a brush wetted with boiling water, to give them a gloss; they are, lastly, stove-dried for sale. This furnishes the palest and best glue.

As soon as the liquor of the first boiling has drained off, the undissolved portion of skins, &c., left in the copper is treated with fresh water, and the whole operation is repeated again and again, as long as any gelatinous matter is extracted. In this way a second and other inferior qualities of glue are obtained. The product from dried glue-pieces is about 50%.

_Var._ These chiefly depend on the care with which the process is conducted. HATMAKERS' GLUE is prepared from the tendons of the legs of neat cattle and horses. It is brown, opaque, and soft; and grows moist in damp weather, but it does not render felt brittle like the other varieties. FISH GLUE is made in like manner from various membranous and solid parts of fishes. PARCHMENT GLUE is prepared from shreds or shavings of parchment, vellum, white leather, &c., dissolved by boiling them in water. It is scentless, and nearly colourless.

_Qual._ The best glue is transparent, nearly colourless, and tasteless, has very little smell, even when melted, and is extremely adhesive. The presence of more than a trace of alum is objectionable; an undue quantity may be easily detected by the usual tests. The strongest glue is that obtained from skins, more especially from the hides of oxen and cows. That obtained from the bones, cartilages, and tendons, is weaker.

=Glue, Liq'uid.= _Prep._ (Dumoulins.) Soft water, 1 quart; best pale glue, 2 lbs.; dissolve in a covered vessel by the heat of a water bath, cool, and add, gradually, of nitric acid (sp. gr. 1·335), 7 oz.; when cold put it into bottles. Very strong, and does not gelatinise. For the 'LIQUID GLUE' sold in the shops, see CHINESE CEMENT.

=Glue, Marine.= _Prep._ 1. India rubber (cut small), 1 part; coal tar or mineral naphtha, 12 parts; digest in a covered vessel with heat and agitation, and when the solution is complete, add of powdered shell-lac, 20 parts; continue the heat and stirring until perfect liquefaction has taken place, and pour the fused mass, whilst still hot, on slabs of polished metal or stone, so as to form thin sheets. For use, it is heated to its melting-point (248° to 250° Fahr.) in an iron vessel, and applied in the liquid state with a brush. Employed in ship-building, &c.

2. Caoutchouc, 15 to 20 gr.; chloroform, 2 fl. oz.; dissolve, and add of powdered mastic, 1/2 oz. It must be kept well corked and in a cool place, to prevent loss by evaporation. Used for small, fine work.

=Glue, a New.= Ordinary glue is dissolved in nitric ether, and a little bit of caoutchouc added. This solution forms a very strong glue, and does not get thick or pasty. ('Dengler's Journal.')

=Glue, Port'able.= _Syn._ BANK-NOTE GLUE. MOUTH G., INDIAN G.; COLLE À BOUCHE, Fr. _Prep._ From the best pale glue, 1 lb.; water, q. s.; dissolve in a double glue-pot or water bath, and of pale-brown sugar, 1/2 lb., continue the heat until the mixture is complete, and pour it into moulds; or pour it on a marble slab, and when cold cut it into small pieces and dry them in the air. This glue is very useful to draughtsmen, architects, &c., as it dissolves almost immediately in warm water, fastens paper, &c., without the process of damping, and may be softened for many purposes with the tongue. When great strength not required, 4 oz. more of sugar may be used.

=GLU'TEN.= _Syn._ GLUTIN. A peculiar substance found in the grain of wheat. It is composed of true vegetable fibrin and a small quantity of gliadin. It is prepared by washing paste made of the flour of wheat or rye in successive waters until all starchy matter is removed. The paste may be conveniently enclosed in a bag of fine linen during the washing.

_Prop., Uses._ Gluten is believed to be eminently nutritious. It is the presence of gluten in wheaten flour that imparts to it its viscidity or tenacity, and confers upon it its peculiar excellence for the manufacture of MACARONI, VERMICELLI, and similar pastes. The superiority of wheaten over other bread depends upon the greater tenacity of its dough, which during the fermentation is puffed up by the evolved carbonic acid, and retained in its vesicular texture so as to form a light loaf.

Gluten is greyish coloured, and extensible whilst fresh and moist, like caoutchouc. It turns blue when mixed with guaiacum resin.

=Gluten Bread.= _Prep._ 1. From wheat flour which has been deprived of about 2-3rds of its starch by washing it with water.

2. From gluten flour. Recommended in diabetes.

=Gluten Choc'olate.= (Gentile's.) A mixture of cocoa and gluten flour. As a nutritious and appropriate food in diabetes.

=Gluten Flour.= _Prep._ 1. From the waste gluten of the starch works, washed, dried, and ground.

2. (Gentile's.) From the last, mixed with about an equal weight of wheat flour.

=GLYC'ERIN.= C_{3}H_{3}O_{3}. _Syn._ GLYCERIN, HYDRATED OXIDE OF GLYCERYL; GLYCERINUM, L. A sweet syrupy liquid formed during the saponification of oils and fats.

_Prep._ 1. Olive oil (or other suitable oil), protoxide of lead, and water are heated together until an insoluble soap of lead (lead plaster) is formed. The glycerin remains in the aqueous liquid. As this crude solution of glycerin is produced in great quantities in the manufacture of lead plaster, the operative chemist has only to purify it. This may be done as follows:--

The water and washings from lead plaster are mixed together, filtered, and submitted to the action of a stream of sulphuretted hydrogen to throw down the lead; the supernatant liquor is decanted from the precipitate, filtered, and evaporated to the consistence of a syrup in a water bath. To render it quite pure it is diluted with water, decoloured with a little animal charcoal, filtered, and again evaporated to the consistence of a thin syrup, after which it is further evaporated in vacuo, or over sulphuric acid, until it acquires the sp. gr. 1·265.

2. (M. Bruère-Perrin.) From the sweet liquor of the stearine works (a product of the process of lime-saponification). The quantity of lime present in the sample is first determined by means of oxalic acid, and the proportion of sulphuric acid necessary for its saturation at once calculated and added; the crude liquor is then concentrated in a tinned-copper vessel, evaporation being promoted by brisk agitation, until the sp. gr. sinks to 10° Baumé; it is next cooled and filtered, and accurately neutralised (if it is required) with carbonate of potassa, after which it is evaporated to the sp. gr. 24° Baumé; on cooling, it deposits gelatinous sulphate of potassa; the whole is now filtered, the deposit on the filter washed with a little very weak spirit and water, the filtrate and washings mixed together and evaporated, as before, with agitation, until the sp. gr. 28° Baumé, whilst hot (36° cold), is attained, when the whole is allowed to cool; the clear liquid is, lastly, decanted and filtered. In this state it has an amber colour, but may be rendered colourless and odourless by rediluting it with water, treating it with animal charcoal, filtering, and again evaporating to a proper consistence.

3. By saponifying olive oil with caustic alkali, decomposing the resulting soap with dilute sulphuric or tartaric acid, evaporating the aqueous portion to dryness (nearly), dissolving out the glycerin with cold rectified spirit, and filtering and evaporating the solution as before.

4. The residuary liquor of a soap manufactory is evaporated, and treated with alcohol to dissolve out the glycerin. The spirit is then evaporated off, the glycerin diluted with water, and finally boiled repeatedly with animal charcoal until all colour and odour are removed.

_Obs._ The products of the above processes are nearly pure, but that of Price's patent process, described below, is to be preferred to any of them.

5. (Commercial.) From sweet stearin-liquor, by precipitating the lime by a stream of carbonic acid gas, or by a solution of carbonate of soda, carefully avoiding adding the latter in excess; the liquor is then boiled a little, filtered, evaporated to a syrupy consistence, and again filtered. This is the common glycerin of the shops. It may be further purified as above.

6. (PRICE'S GLYCERIN--Patent dated 1854.) Superheated steam of from 550° to 600° Fahr.) is introduced into a distillatory apparatus containing palm oil or other fatty body. The action of the steam effects the decomposition of the fat, and glycerin and the fatty acids distil over together but no longer in combination. In the receiver the condensed glycerin, from its higher specific gravity, sinks below the fatty acids. Sufficient steam must be supplied, and the temperature nicely regulated. The glycerin is concentrated by evaporation, and if discoloured, it is redistilled. It is usually prepared with sp. gr. 1·24, and then contains 94% of anhydrous glycerin. It can, however, be concentrated to sp. gr. 1·26 when it contains 98%.

_Prop._ Pure glycerin is a colourless, odourless, uncrystallisable liquid, sweet to the taste, and of a syrupy consistence; it mixes with water in all proportions; it is unctuous and emollient, and softens bodies, like oil, but without greasing them; it does not evaporate or change in the air at ordinary temperatures, and is not susceptible of rancidity or spontaneous fermentation; mixed with yeast and kept in a warm place, it is gradually converted into propionic acid; a strong heat decomposes it, with the production of acrolein; it is neutral to test-paper, and possesses neither basic nor acid properties; it is easily charged with the aroma of the essential oils, and may be combined with soap, and many other substances, without undergoing change. Sp. gr., 1·27 (see _above_).

MM. Champion and Pellet recommend the following methods for testing the purity of glycerin, as being convenient in application, and giving accurate results.

_Qualitative Test._ The glycerin diluted with twice its weight of water is treated in the cold.

(1.) With tribasic acetate of lead. If an abundant precipitate be formed, and rapidly deposited, the presence of a proportion of foreign matters may be assumed which would make it unsuitable for use in various applications, such as the manufacture of nitro-glycerin, &c. The crude glycerin obtained in treating fats with sulphuric acid is frequently thus contaminated. These foreign matters result from the action of sulphuric acid at a high temperature (about 110° C.) upon the fatty matter itself or on the impurities it may contain.

(2.) Glycerin obtained by calcareous saponification, also may contain oleate of lime. This may be detected with oxalate of ammonia, which throws down the lime as a clearly perceptible precipitate.

The colour of glycerin is in no way an index of the purity of the product. In all cases it is useful to be assured of the neutrality of the glycerin.

The preceding tests are suited for glycerins more or less impure, but not adulterated. According to the authors' experiments the tribasic acetate of lead separates all the foreign substances due to normal impurity of the product or alteration in the glycerin during its manufacture. Any addition of glucose may be detected by Fehlings' solution.

_Quantitative Test._ This test should comprehend the determination of the water, the foreign organic matter, the lime, and the glycerin.

In the following table the authors have given the density of various mixtures of water and glycerin, comparatively with the degrees Baumé, and also the proportions of water corresponding to the densities. They state, that these determinations have been verified by means of pure anhydrous glycerin, prepared by keeping glycerin for several hours at a temperature of 160° C, and terminating the operation _in vacuô_. The density found was in accord with that given by Berthelot, namely, 1·264.

_Estimation of Organic Matter._ Fifty grams of glycerin diluted with water are treated with an excess of tribasic acetate of lead, and the precipitate collected on two tared filters, and the lead compound weighed. The whole is then calcined, the residue treated with nitric acid, and then with sulphuric acid, and from the sulphate of lead is calculated the quantity of oxide of lead, that was in combination with organic matters, and consequently the proportion of the latter, which rarely exceeds 1 to 1·5 per cent.

Lime may be estimated in the usual manner by oxalate of ammonia.

------------------------------------------------------------------------
Hydrometer | Areometer | Water, | Hydrometer | Areometer | Water,
Weight of | Degrees, | per Cent.| Weight of | Degrees, | per Cent.
Litre. | Baumé. | | Litre. | Baumé. |
-----------------------------------|------------------------------------
1264·0 31·2 0·0 | 1235·0 28·6 11·0
1262·5 31·0 0·5 | 1233·5 28·4 11·5
1261·2 30·9 1·0 | 1232·2 28·3 12·0
1260·0 30·8 1·5 | 1230·7 28·2 12·5
1258·5 30·7 2·0 | 1229·5 28·0 13·0
1257·2 30·6 2·5 | 1228·0 27·8 13·5
1256·0 30·4 3·0 | 1227·0 27·7 14·0
1254·5 30·3 3·5 | 1225·5 27·6 14·5
1253·2 30·2 4·0 | 1224·2 27·4 15·0
1252·0 30·1 4·5 | 1223·0 27·3 15·5
1250·5 30·0 5·0 | 1221·7 27·2 16·0
1249·0 29·9 5·5 | 1220·2 27·0 16·5
1248·0 29·8 6·0 | 1219·0 26·9 17·0
1246·5 29·7 6·5 | 1217·7 26·8 17·5
1245·5 29·6 7·0 | 1216·5 26·7 18·0
1244·0 29·5 7·5 | 1215·0 26·5 18·5
1242·7 29·3 8·0 | 1213·7 26·4 19·0
1241·2 29·2 8·5 | 1212·5 26·3 19·5
1240·0 29·0 9·0 | 1211·2 26·2 20·0
1239·0 28·9 9·5 | 1210·0 26·0 20·5
1237·5 28·8 10·0 | 1208·5 25·9 21·9
1236·2 28·7 10·5 |
------------------------------------------------------------------------

The authors consider that industrially the tribasic acetate of lead might be used for the removal of organic matter from crude glycerin.

After separation of the precipitate, excess of the lead salt could be removed by a current of sulphuretted hydrogen, and during the concentration of the glycerin, the acetic acid set free would be volatilized with injury to the product. The lead salt might be regenerated by calcination, and again converted into acetate.[337]

[Footnote 337: 'Moniteur Scientifique,' Quesneville [3], vol. iii, p. 1033.]

The following quantitative test which it is said will detect upon concentration of the fluids, one-tenth per cent. of glycerin in beer; one per cent. in sherry, one per cent. in milk, and five per cent. in treacle, is based upon a fact observed by Iles, viz. that borax when treated with glycerin, gives to a Bunsen flame the green colour characteristic of boracic acid. The method of its application as given by Messrs Senier and Lowe is as follows:--The suspected solution is rendered alkaline by dilute soda, and a borax bead placed in it for a short time. The bead is then held in a Bunsen flame, and if the solution contains one per cent. of glycerin a distinct reaction is observed. Erythrite and glycol give the same colour.

If a small quantity of glycerin from which the fatty acids have not been removed, be poured into the palm, and rubbed between the hands, a peculiar fetid, mouse-like odour will be perceived.

_Uses, &c._ Glycerin is extensively employed as an excipient for medicines (see GLYCEROLES), also, either alone, or in lotions, baths, &c., as a soothing emollient, and is added to poultices and dressings instead of oil, to prevent their hardening. Diluted with water, it often succeeds in allaying itching and irritation of the skin when all other means fail. As a cosmetic, either made into a lotion or added to soap (glycerin soap), or used in small quantities (along with the water employed in washing), it imparts a healthy clearness and a sensation of softness and coolness to the skin, which is very agreeable and refreshing. It is the best remedy known for chapped nipples, hands, lips, &c.; all of which may be prevented by its use as an article of the toilet. Glycerin is sometimes used as a sweetening agent, as a substitute for syrup.

Glycerin is employed for a great variety of purposes other than medicinal; such, for example, as for:--Keeping clay moist for the modeller, for preventing mustard from drying up, for keeping snuff damp, for the preservation of fruit, for sweetening liqueurs, wine, beer, and malt extracts. It is also used as a lubricant for some kinds of machinery, more especially for watch and chronometer works, because it is unaffected by contact with the air, does not thicken at a low temperature, and is without action on such metals as copper, brass, &c. Glycerin is also an ingredient in copying inks. It renders printing ink soluble in water; indeed it is an excellent solvent for many substances, including the Tar-colours (aniline blue, cyanine, aniline violet, and alizarine), and arsenious acid. It is also added to the pulp of paper in order to render it soft and pliable. It is said that leather driving-belts made as they usually are of weakly tanned leather, when kept in glycerin for twenty-four hours are not so liable to fray. A solution of glycerin in water is now largely used instead of water alone for the purpose of filling gas metres, as such a solution does not freeze in winter nor evaporate in summer. It has also been used for the compasses on board screw-steamers, in order to protect the inner compass-box, against the vibrations caused by the motion of the propeller. It is also employed for the preservation of anatomical preparations, and for mounting microscopic specimens; as well as for rendering wooden casks impervious to petroleum or other oils; as well as for the preparation of artificial oil of mustard, or sulpho-cyan-allyl, which is made by treating glycerin with iodide of phosphorus, whereby iodide of allyl is formed, which on being dissolved in alcohol, and next distilled with sulpho-cyanide of potassium, yields sulpho-cyan-allyl. When treated with concentrated nitric acid, glycerin yields nitro-glycerin.[338]

[Footnote 338: Wagner's 'Chemical Technology.']

Even the above long list does not exhaust the many useful purposes to which glycerin is now applied.

=Glycerin Cream for Chilblains.= Equal parts of glycerin, soft soap, and cherry-laurel water, mixed together.

=Glycerin Cream with Camphor.= Glycerin, 2 parts; camphor, 1 part; rectified spirit, 1 part. Mix. For chilblains.

=Glycerin Jelly for Microscopic Mounting.= ('Ed. Pharm. Journal.') Soak any quantity of good clean gelatine in cold water for three or four hours. Pour off the superfluous water, and melt the gelatine at a gentle heat; when melted filter through flannel, and to the filtrate add an equal quantity of Price's gelatin.

The above forms a good firm jelly, requiring little trouble in securing the cover.

=Glycerin Ointment.= Glycerin, 8 parts; spermaceti, 4 parts; white wax, 1 part; oil of almonds (fixed), 16 parts. Add the glycerin to the melted ingredients, and stir briskly till cold. For chaps and excoriations.

=GLYCEROLE.= A pharmaceutical preparation, in which glycerin is employed as the excipient.

=Glycerole of Belladonna.= _Syn._ GLYCERINUM BELLADONNÆ. _Prep._ (Par. Codex.) Extract of belladonna, 1 oz., glycerole of starch, 10 oz. (by weight); rub together until perfectly smooth. Glyceroles of hemlock, henbane, and opium are ordered by the Paris Codex to be prepared in the same manner.

=Glycerole of Borax.= (B. P.) _Syn._ GLYCERINUM BORACIS, L. 1 of borax in 4-1/2 of glycerin.

=Glycerole of Carbolic Acid.= (B. P.) _Syn._ GLYCERINUM ACIDI CARBOLICI, L. 1 of acid in 4-1/2 of glycerin.

=Glycerole of Gallic Acid.= (B. P.) _Syn._ GLYCERINUM ACIDI GALLICI, L. 1 of acid in 4-1/2 of glycerin.

=Glycerole of Iodine.= _Syn._ GLYCERINUM CUM IODINIO. _Prep._ (Par. Codex.) Dissolve 5 parts of iodide of potassium and 1 part of iodine in their own weight of water, and add to 40 parts of glycerin (by weight). Applied in skin diseases.

=Glycerole of Iodide of Potassium.= _Syn._ GLYCERINUM POTASSII IODIDI. _Prep._ (Par. Codex.) Iodide of potassium, 2 parts, glycerole of starch, 15 parts (by weight); dissolve the iodine in its own weight of water, and add to this glycerole of starch.

=Glycerole of Starch.= (B. P.) _Syn._ GLYCERINUM AMYLI, L. 1 of starch in 8-1/2 of glycerin.

=Glycerole of Tannic Acid.= (B. P.) _Syn._ GLYCERINUM ACIDI TANNICI, L. 1 of acid in 4-1/2 of glycerin.

=Glycerole of Tar.= _Syn._ GLYCERINUM PICIS LIQUIDÆ. _Prep._ (Par. Codex.) Purified tar, 1 oz. (by weight), glycerole of starch, 3 oz. (by weight).

=GLYCOARNICIN.= A radical cure for gangrene and tubercle (Zeller). 40 grammes clarified honey, with 35 grammes of a tincture of fresh arnica herb, made with weak brandy. (Hager.)

=GLYCOBLASTOL= (Professor Kletzinsky, Vienna). An extract of the pericarps of cayenne pepper, made with glycerine, diluted with a little water, and perfumed with a trace of pleasant-smelling oil containing a suspicion of patchouli. (Hager.)

=GLYCOCINE.= _Syn._ GLYCOLL. SUGAR OF GELATIN. (C_{2}H_{5}NO_{2}). This is one of the products of the decomposition of gelatin when boiled with dilute sulphuric acid; after the acid is removed by means of barium carbonate, the glycocine may be procured in crystals by evaporating the solution.

It may also be obtained by heating gelatin with a solution of potash or of soda. It is, however, most easily separated in a state of purity by boiling hippuric acid for half an hour with hydrochloric acid; as the liquid cools benzoic acid is separated in abundance, and glycocine remains in combination with hydrochloric acid; on the addition of absolute alcohol, after the solution has been concentrated by evaporation and super-saturated with ammonia, pure glycocine is deposited in minute crystals.

Pure glycocine has a sweet taste, inferior to that of cane sugar. It is soluble in about 400 parts of cold water, less soluble in rectified spirit, and insoluble in absolute alcohol and in ether. It is not susceptible of the alcoholic fermentation.

=GLYCYR'RHIZIN.= _Syn._ LIQUORICE SUGAR. An uncrystallisable variety of sugar obtained from the root of common liquorice (_Glycyrrhiza glabra_). It is yellow, transparent, soluble in both water and alcohol, and is not susceptible of the vinous fermentation.

=GLYSTER.= See Enema.

=GNATS and MOS'QUITOES.= Smoke and strong fumes of any kind will drive away these insects. If you only burn a piece of brown paper in an enclosed space where they are, they soon after 'settle,' and appear to become so stupefied as to remain inactive for some time after. In those parts of the New World where mosquitoes abound, tobacco smoke is commonly had recourse to in-doors, and large fires made of brush-wood or under-wood out-of-doors. Old travellers, when compelled to bivouac during the season in which they are troublesome, are very careful to keep close on the 'lee' of these fires.

=GOA POWDER.= See ARAROBA.

=GOITRE.= _Syn._ DERBYSHIRE NECK; BRONCHOCELE, TRACHEOCELE; HERNIA BRONCHIALIS, L. A tumour on the fore part of the neck. It sometimes occurs in Derbyshire, and is endemic in the Alps and several other mountainous districts. Iodine and the iodides appear to be the only substances capable of curing or even arresting the progress of this disease.

There seems little doubt that goitre arises from drinking water rendered hard by the presence of magnesian and lime salts.

The disease called cretinism, which is a peculiar form of idiocy, is in some countries more particularly frequently associated with goitre. Both these maladies prevail in Wurtemberg, Saxony, Silesia, the Tyrol, Carynthia, Galicia, Austria, and Switzerland. In England, goitre seems principally confined to the magnesian limestone district extending from Nottingham to the Tyne; it also prevails in a smaller degree in Derbyshire, Norfolk, Cambridge, and Somersetshire, where a few scattered cases of cretinism are to be met with. Goitre is very much more general than is usually supposed in France. In Asia, it is to be found amongst the inhabitants of Chinese Tartary, Thibet, and Ceylon, and in India amongst the dwellers in the valleys and extensive plains that lie at the foot of the Himalayan mountains.

The disease is likewise known to exist in many parts of Africa; goitre is also far from uncommon in certain districts of North America; whilst in South America it is met with amongst the people inhabiting the plateaus of New Grenada, which comprise localities differing so greatly in climatic conditions, as deep and humid valleys, and arid plains almost or entirely destitute of verdure.

Goitre is a disease that may be very rapidly and readily set up. Bally says he has known certain waters in Switzerland produce it even in eight or ten days; and the French medical journals contain many similar instances of its early development.

=GOLD.= Au. _Syn._ AURUM; OR, Fr.; GOLD, Ger.) Gold is the most valuable and, probably, the longest known of all the metals. From the remotest period it has been esteemed for its beauty and permanence, and has been taken as the standard measure of value amongst all civilised nations. An account of the uses of gold in the arts, and its influence on society in all ages, as a symbol of wealth and an article of ornament and utility, would embrace the whole history of mankind. At the present day it alike contributes to the conveniences, comforts, and luxuries of life; as often exciting the baser passions of the human heart as promoting the cause of benevolence and virtue.

Gold is found almost invariably in the metallic state. It occurs as gold dust in the sands of various rivers, and in the alluvial soil of auriferous districts, from both of which it is obtained by the simple process of washing. Traces of it are constantly found in the iron and other pyrites of the more ancient rocks. Sometimes it occurs beautifully crystallised in the cubic form, associated with quartz, oxide of iron, and other substances, in regular veins. In the gold fields of California and Australia lumps of nearly pure gold have been discovered in abundance during the last few years. In the former country a mass of gold weighing 28 pounds was found, whilst in our own colonies one weighing 106 pounds was dug out of a quartz rock, near Bathurst. The latter contained upwards of 91% of pure gold, and nearly 8-1/2% of silver; being as pure as the English sovereign, or, in trade language, '22 carats fine.'

_Prep._ This consists merely in the separation of the gold and its subsequent purification. Formerly, the auriferous sulphides, if very poor, were first roasted, then fused into 'mattes' and again roasted; they were next melted with lead, and the alloy thus obtained was refined by cupellation. When the ores were very rich, the preliminary calcination and fusion were omitted, and the alloy of lead at once formed. This method (by fusion) does not answer well with auriferous copper pyrites or ores very poor in gold. At the present time the method of amalgamation is principally followed. When a 'vein-stone' is to be wrought for gold, it is reduced to powder (on the small scale by hand, on the large scale in stamping mills), and is shaken in a suitable apparatus with water and mercury; an amalgam of gold is formed, which is then separated from the mixture, and its mercury removed by distillation. The gold is next cast into 'ingots.'

_Refining._--Gold obtained by the first method usually contains a little copper and silver, and frequently tin or iron. Tin may be removed by adding a little corrosive sublimate or nitre to the gold melted in a crucible. The process by amalgamation commonly leaves no other alloy than silver. This metal is removed either in the 'dry way,' by fusing the gold with sulphur or sulphide of antimony; or in the 'wet way,' by 'quartation' and 'parting.' At the Royal Mint, "when gold ingots contain a certain quantity of silver" (say 2% or 3%), "instead of leaving it, as formerly, to constitute a part of the standard alloy, it pays to extract it, and to substitute copper in its place. To get the silver out of the said ingots, they are melted with about 3 parts of silver--the resulting alloy is granulated and boiled with sulphuric acid--the gold remains untouched, and all the silver is dissolved and converted into sulphate.... The sulphate of silver is then decomposed by the immersion of copper plates; the silver is precipitated in a fine, crystalline powder, washed, pressed into masses, and melted, and so affords PURE SILVER, which is afterwards made standard by alloying it with copper, and is used for coinage. The resulting sulphate of copper (which exists in the solution) is then crystallised, and sold." (Brande.) "By first exhausting the gold with nitric acid, and then boiling it in sulphuric acid, some two or three thousandth part of silver which escaped the action of the nitric acid is dissolved out, and perfectly pure gold is obtained." (Ure.)

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 99-1/2% 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 1/10th 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.

[Greek: a]. 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.

[Greek: b]. 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.

[Greek: g]. 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 2-1/2 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 1-1/2 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.

[Greek: d]. 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.

[Greek: e]. 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 (1-1/2 × 5 inches), twisted on a quill, and submitted to parting with 2-1/2 oz. and 1-1/2 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_, 1/4 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:--=