Redetermination of (NH(4))(2)HAsO(4).

In comparison with the original determination based on Weissenberg film data [Khan et al. (1970 ▶). Acta Cryst. B26, 1889-1892], the current redetermination of diammonium hydrogenarsenate(V) reveals all atoms with anisotropic displacement parameters and all H atoms localized. This allowed an unambiguous assignment of the hydrogen-bonding pattern, which is similar to that of the isotypic phosphate analogue (NH(4))(2)HPO(4). The structure of the title compound consists of slightly distorted AsO(3)(OH) and NH(4) tetra-hedra, linked into a three-dimensional structure by an extensive network of O-H⋯O and N-H⋯O hydrogen bonds.