A second polymorph of 2-aminopyridinium dihydrogenphosphate.

In the title compound, beta-C5H7N2+.H2PO4-, the tetrahedral dihydrogenphosphate moieties are linked into double chains by O-H...O hydrogen bonds, and the organic species crosslink the chains into sheets by way of N-H...O bonds. The resulting structure is quite different from that of the previously described alpha polymorph of this stoichiometry [Czapla, Dacko & Waskowska (2003). J. Phys. Condens. Matter, 15, 3793-3803].