Sodium magnesium sulfate decahydrate, Na(2)Mg(SO(4))(2).10H(2)O, a new sulfate salt.

The structure of synthetic disodium magnesium disulfate decahydrate at 180 K consists of alternating layers of water-coordinated [Mg(H(2)O)(6)](2+) octahedra and [Na(2)(SO(4))(2)(H(2)O)(4)](2-) sheets, parallel to [100]. The [Mg(H(2)O)(6)](2+) octahedra are joined to one another by a single hydrogen bond, the other hydrogen bonds being involved in inter-layer linkage. The Mg(2+) cation occupies a crystallographic inversion centre. The sodium-sulfate sheets consist of chains of water-sharing [Na(H(2)O)(6)](+) octahedra along b, which are then connected by sulfate tetrahedra through corner-sharing. The associated hydrogen bonds are the result of water-sulfate interactions within the sheets themselves. This is believed to be the first structure of a mixed monovalent/divalent cation sulfate decahydrate salt.