Simple method for the determination of gypsum, with some observations on the solubilities of gypsum, anhydrite, calcite and dolomite

Abstract

A rapid method is presented for the determination of gypsum and related minerals in natural and synthetic materials, based on the extraction of calcium from the matrix material using slightly ammoniacal water as a solvent with subsequent complexometric titration of the calcium using EDTA. The results compare reasonably well with those obtained by the conventional gravimetric procedure. The interferences due to other sparingly soluble calcium compounds, such as calcite and dolomite, commonly found in conjunction with gypsum were examined, as were the solubilities of anhydrite, calcite and dolomite in both water and sodium chloride solution. The method is particularly suitable for industrial control and deposit assessment purposes.