Mechanism of dehydration of calcium sulphate dihydrate. Application of the helium pyknometric technique

Abstract

A technique involving helium diffusion has been applied to a study of the dehydration of CaSO₄·2H₂O in vacuo. New evidence supports arguments that removal of water from the β-hemihydrate is ‘zeolite-like’ and that small amounts of tightly held water block entrances to microspace in the β-hemihydrate structure. An appraisal is given of density measurements and changes due to dehydration processes.