Dicaesium magnesium bis-(dihydrogen phosphate(V)) dihydrate.

The title compound, Cs(2)Mg(H(2)P(2)O(7))(2)·2H(2)O, is isostructural with the related known isoformular phosphates. The crystal framework consists of corner-sharing MgO(6) and H(2)P(2)O(7) polyhedra, leading to tunnels parallel to the b-axis direction in which Cs(+) ions are located. The H(2)P(2)O(7) unit shows a bent eclipsed conformation. The Mg(2+) ion lies on an inversion center. The water molecules form hydrogen bonds to O atoms of two different dihydrogenphosphate ions, which are further hydrogen bonded to symmetry-equivalent dihydrogenphosphate ions.