Hydro­nium (3-oxo-1-phosphono-1,3-dihydro­isobenzofuran-1-yl)phospho­nate

In the title compound, H(3)O(+)·C(8)H(7)O(8)P(2) (−), the anions form inversion dimmers by way of pairs of O—H⋯O hydrogen bonds involving the phospho­nic functions and via the hydro­nium cation. Further O—H⋯O links involving the hydronium cation play a prominant part in the cohesion of the crystal structure by building bridges between bis­phospho­nate pairs, forming infinite ribbons along the b-axis direction and by cross-linking these ribbons perpendicularly along the a-axis direction, forming an infinite three-dimensional hydrogen-bond network. The benzene ring and the C=O atoms of the furan ring are disordered over two sets of positions of equal occupancy.