Morphology and dehydration mechanism of transition metal sulfate heptahydrates

Abstract

Processes and thermodynamic parameters of dehydration of transition metal (Ni, Co, and Fe) sulfate heptahydrate crystals grown in aqueous solutions have been investigated by optical thermomicroscopy, X-ray analysis, and differential scanning calorimetry. Values of temperature and specific heat of the first stage of dehydration have been determined, as well as the conditions under which the process was reversible. The morphology of the common topochemical reaction, as well as the mechanism of this reaction, has been characterized. The dehydration process has been shown to depend on multiple physical parameters and to consist in the growth of non-oriented crystals of the new phase with concomitant exudation of the water of crystallization.