Thermal Investigations on Alunite and Its Mixtures with Quartz and Dickite

M.-A. Kashkai and I. A. Babaev
Ulitsa Husi Hadzhieva II, apt. 6, Baku-5, U.S.S.R.

Summary: The thermal decomposition of alunite and of mixtures of alunite with dickite or quartz or both has been studied, and X-ray determinations of the products at various stages of the decomposition have been made. Between 600 and 700°C the product from alunite is a mixture of anhydrous alum and amorphous alumina; between 700 and 770°C the anhydrous alum breaks down into aluminium sulphate and alkali sulphate; then in the prominent 850°C endothermic reaction three-quarters of the sulphate is lost, leaving a mixture of alkali sulphate and γ-alumina. The area of the 850°C endothermic peak may be used as a measure of the percentage of alunite in alunitized rocks (alunite-quartz-dickite mixtures).

Mineralogical Magazine; March 1969 v. 37; no. 285; p. 128-134; DOI: 10.1180/minmag.1969.037.285.13
© 1969, The Mineralogical Society
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