Cadmium copper tetrachloride tetrahydrate

The double salt [CuCl₂(H₂O)₂{CdCl₂}]·2H₂O crystallizes in the triclinic rather than the monoclinic system as reported previously. The structure consists of sheets in the ac plane with slightly distorted octahedral CdCl₆ [Cd—Cl 2.5813 (8)–2.6943 (8) Å] connected by Cd—Cl—Cd bridges in the Cd equatorial plane along a , and by Cd—Cl—Cu bridges to layers of square‐planar CuCl₂(H₂O)₂ along c . There are long axial Cu—Cl interactions of 2.8623 (7) Å and additional water of hydration is hydrogen bonded to coordinated water and chloride ligands. The additional water connects the ac sheets into a three‐dimensional network. Both Cd and Cu occupy different sites. The Cu?Cu and Cd?Cd distances are 3.8274 (6) Å.     

Polymorphism of potassium-sodium tartrate tetrahydrate

A geometric model of phase equilibria between NaKC₄H₄O₆ · 4H₂O crystal hydrate polymorphs was suggested. An analytic equation for its thermodynamic potential was obtained, and the temperature dependences of heat capacity and polarization were found. An analytic form of the interrelation between the anisotropic characteristics of NaKC₄H₄O₆ · 4H₂O was obtained, and their temperature dependences were calculated over a wide temperature range including polymorphic transition points.