Monoclinic polymorph of poly[aqua(μ(4)-hydrogen tartrato)sodium].

A monoclinic polymorph of the title compound, [Na(C(4)H(5)O(6))(H(2)O)](n), is reported and complements an ortho-rhom-bic form [Kubozono, Hirano, Nagasawa, Maeda & Kashino (1993 ▶). Bull. Chem. Soc. Jpn, 66, 2166-2173]. The asymmetric unit contains a hydrogen tartrate anion, an Na(+) cation and a water mol-ecule. The Na(+) ion is surrounded by seven O atoms derived from one independent and three symmetry-related hydrogen tartrate anions, and a water mol-ecule, forming a distorted penta-gonal-bipyramidal geometry. Independent units are linked via a pair of inter-molecular bifurcated O-H⋯O acceptor bonds, generating an R(2) (1)(6) ring motif to form polymeric two-dimensional arrays parallel to the (100) plane. In the crystal packing, the arrays are linked by adjacent ring motifs, together with additional inter-molecular O-H⋯O inter-actions, into a three-dimensional network.