Ceramics-Silikáty 39 (3) 87-91 (1995)

REACTIONS OF SILICA WITH ALKALI CHROMATES

J. Hlaváč, K. Marušková

On the basis of experience gained with melting glasses containing chromates in the batch, the authors assume that alkali chromates react at high temperatures in air spontaneously with silica, forming Cr₂O₃ and alkali silicate, and liberating oxygen. The assumption was experimentally verified on mixtures of SiO₂ with sodium and potassium chromates, at 2:1 and 4:1 ratios, using DTA, GTA, X-ray diffraction and gas chromatography of the gaseous reaction products. It has been proved by GTA that the reaction of SiO₂ with Na₂CrO₄ takes place over the range of 1073 to 1120°C, and that with K₂CrO₄ at 1220 to 1360°C.