The crystal structure of magnesium chloride dodecahydrate, MgCl 2 .12H 2 O

Abstract

Magnesium chloride dodecahydrate crystallizes in the monoclinic space group P21/c with unit-cell dimensions a= 8.59, b= 14-40, c= 8.75 A, fl= 129"6 °, D~= 1.241 g.cm-3, Z=2. The phase problem was solved by the direct method. The positions of all atoms except the hydrogen atoms were deduced from the three-dimensional Fourier synthesis, and refined by anisotropic least squares. All the hydrogen atoms are involved in hydrogen bonding and their approximate positions could be deduced from geometrical considerations. The structure consists of [Mg+(H20)6] and [C1-(H20)6] octahedra which are corner-linked in layers and hydrogen-bonded together between these layers. The ionic-bonded cationic octahedra are regular, while the larger hydrogen-bonded anion octahedra are considerably distorted.