Sodium tungstate dihydrate: a redetermination

There have been two previous structure determinations of the title compound, Na2WO4·2H2O: in 1969 [Mitra & Verma (1969). Indian J. Chem. 7, 598–602] and in 1974 [Okada et al. (1974a). Bull. Tokyo Inst. Technol. 120, 7–11]. However, both structures are incorrect according to their entries in the Inorganic Crystal Structure Database [(2007), URL: http://www.fiz-karlsruhe.de/ecid/Internet/en/DB/icsd/index.html]. Despite the high absorption coefficient, the H-atom positions could be observed and refined in the present study. Owing to the accurate analytical absorption correction, all non-H atoms could be refined satisfactorily with anisotropic displacement parameters. There are hydrogen-bonding inter­actions between all H atoms and the O atoms of the tungstate dianion.