Redetermination of MgCrO₄·5H₂O

The CCD-data based redetermination of the crystal structure of the title compound, magnesium chromate(VI) penta­hydrate, confirms in principle the previous study based on precession film data [Bertrand et al. (1971). C. R. Hebd. Seances Acad. Sci. Serie C, 272, 530–533.], but with all atoms refined with anisotropic displacement parameters and with all H atoms localized. This allowed an unambiguous assignment of the hydrogen-bonding pattern. MgCrO₄·5H₂O adopts the MgSO₄·5H₂O structure type. It contains two Mg²⁺ sites on special positions with site symmetry -1, one tetra­hedral CrO₄ group and five water mol­ecules. Four of them coordinate to the Mg²⁺ cation, and one is an uncoordinating lattice water mol­ecule. The octa­hedral environment of the Mg²⁺ cation is completed by two axial O atoms of CrO₄ tetra­hedra. This arrangement leads to the formation of chains parallel to [011]. Adjacent chains are linked through O—H...O hydrogen bonds (one of them bifurcated), involving both the coordi­nating and lattice water mol­ecules, into a three-dimensional network.