Factors affecting the solubility of gypsum. The effect of lime and temperature in different media

The effect of lime on the solubility of gypsum in water and in sodium hydroxide solution at 30, 60 and 100°C has been studied turbidimetrically and by means of X‐ray diffraction analysis. Lime depressed the solubility of gypsum in water only slightly at 30°C and a rise of temperature minimised its effect until its complete elimination. In the absence of alkali the minimum sulphate ion concentration in a supersaturated lime solution and at temperatures in the range 30–100°C is about 1.2gdm −3 . In sodium hydroxide solution neither lime nor temperature played a significant role and the solubility of gypsum was clearly promoted. At temperatures in the range 30–100°C, 0.5g of gypsum dissolved in 100cm 3 of 0.2MNaOH solution.