The temperature dependence of solubility in the NiCl-HO system in the temperature range of 25–60°C has been studied. The temperature ranges of crystallisation of NiCl·6HO and NiCl·4HO compounds have been determined. Single crystals of nickel chloride hexahydrate and tetrahydrate have been obtained, the size and quality of which have allowed the equilibrium faceting and optical spectra to be estimated. A comparative analysis of the thermal stability of the crystal hydrates obtained was carried out. It was found that the transparency band in the short wavelength range for nickel chloride crystals is shifted to the long wavelength range compared to the nickel sulphate crystal.
Komornikov et al. (Wed,) studied this question.