A calorimetric method for the determination of a partial phase composition in calcined gypsum is presented. The method is based on the separation of the reaction heat of the transformation of β-anhydrite III to β-hemihydrate from the main hydration reaction transforming β-anhydrite III to dihydrate. Using the known hydration heats of β-anhydrite III to dihydrate and β-hemihydrate to dihydrate, the content of β-calcium sulfate anhydrite III and β-calcium sulfate hemihydrate as well as the amount of non-hydrating parts in gypsum can be determined. Practical application of the method is illustrated on three industrial products.
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