Thermography of Gypsum

Abstract

A study of gypsum was made using the differential thermal analysis technique. Gypsum and mixtures of gypsum with silica, alumina, iron oxide, dialyzed kaolin, or carbon were analyzed. Furnace atmospheres of air, nitrogen, carbon dioxide, and carbon monoxide were used. Gases evolved at the decomposition temperature of gypsum were analyzed chemically and sample residues were anelyzed by X‐ray diffraction A slight amount of decomposition was observed when gypsum passed from the beta to alpha mineral form of CaSO 4 , but decomposition was not complete even after fusion had started. The addition of 20% carbon to the gypsum and heating in a nitrogen atmosphere caused decomposition, with evolution of CO 2 to start at a temperature as low as 615°C.