Method of producing persilicates of increased stability with high content of hydrogen peroxide or active oxygen

摘要

Persilicates or persilicic acid of increased stability are obtained by practically fully dehydrating the hydrous compounds in vacuo, if desired in the presence of stabilizers such as chloride, sulphide, cyanide, urea, or barbituric acid. Practically fully dehydrating is defined to mean dehydration to a water content of about 1 per cent. The hydrous compounds may be prepared by precipitation from silicate solutions, by adding silicon dioxide hydrate to a metal peroxide, by crystallization from a solution of a silicon compound in hydrogen peroxide, by anodic oxidation, or by cathodic reduction of oxygen. In examples: (1) Hydrogen peroxide is poured over freshly produced silicic acid and the mixture distilled in vacuo to obtain the compound SiO2.H2O2. 2H2O. By continuing the distillation in vacuo on a water bath at higher temperatures, first the monohydrate and finally the anhydrous compound is obtained; (2) Lithium silicate is dissolved in hydrogen peroxide solution and the solution distilled to obtain the compound Li2SiO3.H2O2.H2O, which is then dehydrated in vacuo; (3) Sodium silicate is dissolved in hydrogen peroxide solution and the cooled solution treated with barium chloride to precipitate the compound BaSi2O5.2H2O2 3H2O, which is then dehydrated in vacuo; (4) Lithium peroxide and silicon dioxide hydrate are ground together to a fine powder and the mixture carefully warmed to obtain the persilicate for dehydration; (5) A concentrated solution of sodium metasilicate is subjected to anodic oxidation using platinum foil electrodes. A high current density is employed and the solution cooled. The persilicate produced is dehydrated; (6) A solution of sodium silicate in a solution of hydrogen peroxide is electrolyzed using a lead peroxide anode and a copper amalgam cathode, the current density being very low. Oxygen or gases containing it are blown against the cathode and a negative catalyst such as gelatine is added to avoid production of oxygen. The persilicate produced is dehydrated. In examples 5 and 6, diaphragms may be used, if desired, consisting of asbestos with adhesive and filling materials, or cement materials, or a mixture of aluminium oxide and silicic acid.