Mg2Na2V10O28·20H2O and Mg3V10O28·28H2O

The crystal structures of dimagnesium disodium decavanadate icosahydrate, Mg2Na2V10O28·20H2O, (I), and trimagnesium decavanadate octacosahydrate, Mg3V10O28·28H2O, (II), have been determined by single‐crystal X‐ray diffraction. They crystallize with monoclinic (C2/c) and triclinic () symmetry, respectively. All the Mg2+ cations in (I) and (II) are octahedrally coordinated by six water mol­ecules. The Na+ cations in (I) are coordinated by three water mol­ecules and three O atoms of the decavanadate anions, and link the latter into a three‐dimensional network. The decavanadate anions in (II) are not linked to one another.