Crystal structure of sodium di­hydrogen arsenate

Single crystals of the title compound, Na(H(2)AsO(4)), were obtained by partial neutralization of arsenic acid with sodium hydroxide in aqueous solution. The crystal structure of Na(H(2)AsO(4)) is isotypic with the phosphate analogue and the asymmetric unit consists of two sodium cations and two tetra­hedral H(2)AsO(4) (−) anions. Each of the sodium cations is surrounded by six O atoms of five H(2)AsO(4) (−) groups, defining distorted octa­hedral coordination spheres. In the extended structure, the sodium cations and di­hydrogen arsenate anions are arranged in the form of layers lying parallel to (010). Strong hydrogen bonds [range of O⋯O distances 2.500 (3)–2.643 (3) Å] between adjacent H(2)AsO(4) (−) anions are observed within and perpendicular to the layers. The isotypic structure of Na(H(2)PO(4)) is comparatively discussed.