Redetermination of (NH₄)₂HAsO₄

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 (NH₄)₂HPO₄. The structure of the title compound consists of slightly distorted AsO₃(OH) and NH₄ tetra­hedra, linked into a three-dimensional structure by an extensive network of O—H...O and N—H...O hydrogen bonds.