GB477518A - Process of making alkali sub-silicates - Google Patents

Abstract

Solid sodium or potassium silicates are obtained by mixing together powdered silica and solid caustic alkali in such proportions that the ratio Alk2O : SiO2 is at least one and in the absence of sufficient water to dissolve the alkali, and reacting the mixture at a temperature below the fusion point of the alkali, for example by heating to 175--250 DEG C. Water, if added, should not in general exceed 7 per cent of the reaction mixture. The plastic mass first formed during the reaction is stirred until a granular product is obtained, and the silicate formed may be further heated to 300--600 DEG C. to render it technically anhydrous. By using caustic soda and silica in the ratios 1,25 to 1, 1,5 to 1, and 2 to 1, the meta-, sesqui-, and ortho-silicates respectively are obtained, but their composition may be adjusted if necessary by a treatment with waterglass followed by drying at say 200 DEG C. The silica used may be opal, diatomaceous earth, rock crystal, sand, flint, sandstone, or bye-product amorphous or crystalline forms thereof, hydrated or otherwise. Tri- or di-sodium phosphate, or sodium carbonate or bicarbonate may be incorporated with the silicates when they are to be used as detergents. Specifications 391,407 and 477,578 are referred to.