Fluosilicates

salts of fluosilicic acid, H₂SiF₆. They decompose upon heating—for example, CaSiF₆=CaF₂ + SiF₄. The sodium, potassium, rubidium, cesium, and barium salts are only slightly soluble in water; the characteristic crystals formed are used in quantitative and microchemical analysis. Sodium fluosilicate has found widest practical application, particularly in the manufacture of acid-resistant cement and enamel. A substantial proportion of Na₂SiF₆ is converted into NaF. Sodium fluosilicate is produced from the waste products of superphosphate plants containing SiF₄. Fluosilicates of magnesium, zinc, and aluminum (industrial name, Fluoate) are used to waterproof building stone, since they are readily water-soluble. All fluosilicates, as well asH₂SiF₆, are toxic.