Part 188

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.'