=Soda Silicate= is made from a fusion of 100 parts of sand with 50 parts of soda carbonate and 5 parts of charcoal. The charcoal is added to facilitate the decomposition. The fused mass when cool is transparent and of a pale, bluish, sea-green colour. Upon boiling it in water it dissolves and gives a thick viscid solution called “Water Glass.” This is extensively used in the various arts and manufactures. Textile fabric and woodwork saturated with this solution and dried are rendered fireproof. In the manufacture of artificial stone it forms, with lime and other basic oxides, very stable cements. Mixed with silicious or ganister it forms the well-known fire cements for repairing the cracks in retorts, muffles, etc. Water glass is also used in soap, and colour making, and for preserving eggs. =Potash Silicate= is less used, being more expensive. It is produced from a fusion of 100 parts sand, 60 parts potash carbonate, and 6 parts charcoal. =Lead Silicate= is composed of 100 parts sand and 66 parts of red lead fused together. This silicate is mostly used in the manufacture of soft enamels and artificial gems, and goes under the names of “Rocaili flux,” “strass metal,” and “diamond paste.” There is another form of soluble glass which is a combination of the soda and potash silicates. This is really a double silicate and may be produced by fusing sand 100 parts, soda carbonate 25 parts, potash carbonate 30 parts, and 6 parts of charcoal. This silicate is used in soap making. Soluble glass can also be formed by using sulphate of soda as the alkali. In this case, a larger proportion of the alkaline salt has to be used, also a larger amount of carbon, in order to complete the decomposition of the sulphate. A mixture of sand 100 parts, saltcake 70 parts, and carbon 16 parts would produce sodium silicate. The boron silicate and borate of alumina are two other forms of soluble glass used in their simple states. =The Compound Glasses= may be flint or crystal glass, soda-lime glass, Bohemian glass, pressed glass, and sheet glass. These are the general type of glasses used in the manufacture of domestic glasswares. =Crystal Glass=, which is a silicate of lead and potash, is made from best sand 100 parts, red lead 66 parts, potash carbonate 33 parts, cullet 50 parts, to which a small proportion of potash nitre, arsenic, and manganese dioxide is added. The bulk of English cut-glass table ware and fancy goods are made from this type of glass. It gives very brilliant and colourless results, more especially when cut and polished. A second-rate quality of crystal glass for table ware may consist of a silicate of lead and soda, as follows: sand 100 parts, red lead 66 parts, soda carbonate 25 parts, cullet 50 parts; with small proportions of Chili nitre, arsenic, and manganese.