The ZnSO4.3Zn(OH)2-H2O system. I. Phase formation

The bzs-watersystem, where bzs is an abbreviation for ZnSO4.3Zn(OH)2, has been investigated by chemical, X-ray and thermal analyses. The bzs.5H2O was precipitated from solution. Four discrete lower hydrates, namely, the tetra-, tri-, mono- and hemi-hydrates, and an anhydrate were derived from the pentahydrate . The tetra- and tri-hydrates could be prepared by dehydration of the pentahydrate, either thermally or over desiccants; the monohydrate could only be prepared by dehydration of the higher hydrates over desiccants; the hemihydrate and anhydrate could only be prepared by thermal dehydration. Thermal dehydration of the pentahydrate to compositions between the tri- and hemihydrates resulted in the formation of intergrowth structures. Evidence is provided that the layer structure of the pentahydrate persists throughout the series until dehydroxylation of the anhydrate commences. X-ray powder data for the discrete phases have been indexed.