Hydrated water soluble silicates powders

Sodium Aluminosilicate occurs as a fine, white, amorphous powder, or as beads. It is a series of hydrated sodium aluminum silicates having Na20 Al203 Si02 molar ratios of approximately 1 1 13, respectively. It is insoluble in water and in alcohol and other organic solvents, but at 80° to 100°, it is partially soluble in strong acids and solutions of alkali hydroxides. 

The most important property of sodium and potassium silicate glasses and hydrated amorphous powders is their solubility in water. The dissolution of vitreous alkali is a two-stage process. In an ion-exchange process between the alkali-metal ions in the glass and the hydrogen ions in the aqueous phase, the aqueous phase becomes alkaline, due to the excess of hydroxyl ions produced while a protective layer of silanol groups is formed in the surface of the glass. In the second phase, a nucleophilic depolymerization similar to the base-catalyzed depolymerization of silicate micelles in water takes place. 

Hydrated magnesium silicate (Talc, 3Mg0 4Si02 H20, CAS No. 14807-96-6) is a magnesium silicate commonly referred to as "soapstone". It is obtained from natural sources and may contain a small amount of aluminum silicate. It is composed of MgO (31.7%), Si02 (63.5%), and H2O (4.8%). It is a crystalline nonhygroscopic, odorless, tasteless powder which is practically insoluble in water, dilute mineral acids, dilute solutions of alkali halides, and alkaline hydroxides but is soluble in hot concentrated sulfuric acid. 

Some of the available quaternary ammonium silicates have been listed by Weldes and Lange (19), although the nature of the ion was not disclosed. Molar ratios of Si0j (NR4)20 range from 1,2 1 to 30 1 and silica contents of the solutions from 10 to 45%. Hydrated amorphous powders are also listed with ratios of 15.6 1 and 19.7 1. These dissolve rapidly in water and are remarkably soluble in mixtures of water and water-miscible organic solvents such as acetone and the lower alcohols. 

---