Preparation of crystalline hydrates for low-temperature physics

A number of crystalline hydrates, including two new compounds, RbNiCl3 center dot H2O and RbNiBr3 center dot 6H(2)O, were prepared through spontaneous crystallization in aqueous solutions by evaporating the solvent and were characterized by x-ray diffraction and thermal analysis. The lattice parameters of CsMnCl3 center dot 2H(2)O were found to depend on the CsCI : MnCl2 ratio in the solution. It is shown that even a small (similar or equal to 3%) amount of water sorbed by a dry mixture of NH4Cl and MgCl2 center dot 6H(2)O is sufficient for carnallite formation to reach completion during long-term storage of powder compacts at room temperature.