Glass, Sol′uble

Syn. Water gla ; Vitrum solubile , L. An impure alkaline silicate. Prep. Silica, 1 part; carbonate of pota ium or of sodium, 2 parts; fused together. Carbonate of sodium (dry), 54 parts; carbonate of pota ium (dry), 70 parts; silica, 192 parts; as last. Soluble in boiling water, yielding a fine, transparent, semi-elastic varnish. Carbonate of pota ium (dry), 10 parts; powdered quartz (or sand free from iron and alumina), 15 parts; charcoal 1 part; fused together. Soluble in 5 or 6 times its weight of boiling water; and the filtered solution, evaporated to dryne , yields a transparent gla , permanent in the air. 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 , and silicate of potash, from farine fo ile (an infusorial earth), has published an account of his researches in ‘Dingler’s Polytechnic Journal.’ [334] [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 cheapne with flint (where this latter is abundant) for the preparation of the alkaline silicates, he states that it po e es the advantage over flint of being much more soluble, and of yielding a far more neutral gla ; added to which the production of the silicate is said to be effected with much le 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 nece ary 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 di olves 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 pre ure reaches about three atmospheres, and at the end of about three hours the silica is completely di olved. “For the preparation of silicate of potash for surgical purposes the farine fo ile 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 , with an addition of 10 to 15 per cent. of farine.” Uses. . Soluble gla , in solution, has been used to render textile fabrics le 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 pota a compound (silicate of pota ium) 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 , .