Cooley's Cyclopaedia of Practical Receipts Volume I Part 265

M. F. Capitaine, who, acting upon a suggestion made by Liebig, some twenty years since, has recently taken up the subject of the manufacture of soluble gla.s.s, 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 gla.s.s; 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 122 to 124 which were found to be most advantageous. A reservoir furnished with mechanical agitators, was about two thirds filled with lye, and the necessary quant.i.ty 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 28 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 gla.s.s, with an addition of 10 to 15 per cent. of farine."

_Uses. &c._ Soluble gla.s.s, 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-subst.i.tute 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 Lancas.h.i.+re. The pota.s.sa compound (silicate of pota.s.sium) 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.

=Gla.s.s, Toughened.= _Syn._ VERRE TREMPe. M. de la Bastie's process for converting ordinary, into toughened, tempered, or hardened gla.s.s, may in general terms be said to consist in heating the gla.s.s 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 gla.s.s 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 const.i.tute 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 gla.s.s 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 gla.s.s 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 quant.i.ty 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 gla.s.s, 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 gla.s.s is subjected to M. de la Bastie's process are variable. In some cases the articles subjected to it possess great toughness, and the gla.s.s bears a blow without experiencing any fracture. In other instances, however, a slight fall or blow s.h.i.+vers it to atoms. When the toughened gla.s.s under any circ.u.mstances breaks, it possesses a disadvantage over ordinary broken gla.s.s, in distributing itself into a great number of small, sharply angular fragments.

Another process for toughening gla.s.s, which has been patented by Herr F.

Siemens, consists in heating, and then pressing, and suddenly cooling the gla.s.s 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 gla.s.s 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 gla.s.s consists in heating ordinary gla.s.s 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 gla.s.s is liable to rupture under circ.u.mstances that have not yet been accounted for.

M. de la Bastie conceives that the fragile nature of gla.s.s 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 gla.s.s while in a plastic or fluid condition, but without success; and it was only after various experiments that he was enabled to harden the gla.s.s, 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 gla.s.sy; any fact.i.tious, s.h.i.+ning 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 gla.s.s, 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 ma.s.s flows into a clear gla.s.s; 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 ma.s.s formed by heating together the materials of which gla.s.s 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 alb.u.menoid 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 const.i.tute 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 pa.s.ses 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 brus.h.i.+ng 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 ca.s.sia 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 Wohler, 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 pota.s.sium, 3 parts; expose the mixture to a strong red heat for half an hour, dissolve the calcined ma.s.s 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 quant.i.ty 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 cla.s.sed with the earths. The beryl contains 14% of this substance.

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

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

_Prep._ Glue is princ.i.p.ally 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 const.i.tutes 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 ma.s.s. The clear portion is then run off into another vessel, and a very small quant.i.ty 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 ma.s.ses are turned out upon boards wetted with water, and are cut horizontally into thin cakes with a stretched piece of bra.s.s 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.