Crystal structures of sodium magnesium selenate decahydrate, NaMg(SeO)·10HO, a new selenate salt, and sodium magnesium selenate dihydrate, NaMg(SeO)·2HO.

Metal selenates crystallize in many instances in isomorphic structures of the corresponding sulfates. Sodium magnesium selenate decahydrate, NaMg(SeO)·10HO, and sodium magnesium selenate dihydrate, NaMg(SeO)·2HO, were synthesized by preparing solutions of NaSeO and MgSeO·6HO with different molar ratios. The structures contain different Mg octahedra, i.

Similarities and peculiarities between the crystal structures of the hydrates of sodium sulfate and selenate.

The crystal structures of the two hydrates Na2SeO4·10H2O and Na2SeO4·7.5H2O are studied for the first time. The structures of Na2SO4·10H2O and Na2SO4·7H2O are reinvestigated as a function of temperature with respect to the degree of disorder of the O atoms of SO4(2-) in the decahydrate and the O atom of water in the heptahydrate.