The crystal structure of magnesium chloride dodecahydrate, MgCl2.12H2O

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.