Observations on the texture of the products of the dehydration of calcium sulphate dihydrate

Abstract

Studies of the topography of the surfaces of grains of hexagonal calcium sulphate and calcium sulphate hemihydrate, and of the systems of pores they contain, have been made by electron microscopy and the sorption of oxygen, nitrogen, and argon. As the hemihydrate ages, the area of the apparent surface falls and geometric features develop. Hysteresis loops for the sorption of oxygen contract, showing that the finer pores tend to disappear. The topography and area of the surfaces of grains of hemihydrate are not greatly affected by cycles of dehydration and rehydration, showing that these processes are of the zeolitic type.