Identification of the low-temperature phase transition of some solid cadmium crystallohydrates

Abstract

The cadmium crystallohydrates CdBr2·4H2O and 3 CdSO4·8H2O were investigated in regard to phase and structural changes appearing in the dehydration process. Besides phase changes corresponding to transition to a crystallohydrate of lower hydration degree, the low-temperature phase transition of these samples at about 310 K was especially followed. This phase transition was identified as the congruent melting of these crystallohydrates. The results obtained by IR spectroscopy were compared to those of thermal analysis (DSC, TG). It was shown that in certain cases, where by thermal analysis it was not possible to register this type of crystallohydrate phase transition, IR spectroscopy could be applied. © 1985.