ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 44, (3) 104 - 108 (2000)


PRODUCTION OF CALCIUM SULPHATE α-HEMIHYDRATE FROM CITROGYPSUM IN UNHEATED SULPHURIC ACID SOLUTION
 
Kostić-Pulek Aleksandra, Marinković Slobodanka, Logar Vesna, Tomanec Rudolf, Popov Svetlana
 
Faculty of Mining and Geology, University of Belgrad, Djućina 7, 11000 Belgrade, Yugoslavia

Alpha-hemihydrate of calcium sulphate can be obtained by suspending gypsum in boiling or almost boiling aqueous solution of an inorganic acid salts or sulphuric acid at atmospheric pressure. Our task was to try to obtain it from citrogypsum in unheated solution of this acid. The experiment proved it possible if 10, 15, 20, 30, or 40 wt.% solution was used, and that the resulting alpha-hemihydrate developed at various ratios and had different properties, depending on the acid solution concentration and the gypsum/acid solution mixing ratio. An alpha-hemihydrate composed of smooth, compact, acicular monocrystals, which according to reference data promises the best utilitarian aspect, was obtained using 20 wt.% acid solution at 0.25 g cm⁻³ mixing ratio.


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