title: Hydrogen 4-ammonio-phenyl-phospho-n-ate.
abstract: The title compound, C(6)H(8)NO(3)P, is isostructural with p-arsanilic acid. It exists as the zwitterion H(3)N(+)C(6)H(4)PO(3)H(-). In the crystal, mol-ecules are linked by O-H⋯O and N-H⋯O hydrogen-bond bridges, giving a three-dimensional network structure. The strongest hydrogen bonds are formed between adjacent PO(3)H groups with O⋯O distances of 2.577 (2) Å.
authors.affiliation: Institut für Chemie, Naturwissenschaftliche Fakulät II, Martin-Luther-Universität Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120 Halle,  Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Thiele
authors.forename: Christoph
authors.initials: C
authors.lastname: Wagner
authors.forename: Kurt
authors.initials: K
authors.lastname: Merzweiler