In (NH4)H2P02 [Cmma, a = 7.515(6), b = 11.50(1), c = 3.988(4) A, Z = 4 J the anion has accur,ately C2v symmetry, with P-O 1.500 A and a o-P-Q angle of U5.1°. In (CH6N3)H2P02 [Pnam, a = 9.561(8), b = 7.401(5), c = 8.541(5) A, Z = 4 J the anion occupies a site of symmetry m, with similar dimensiori. In botli compounds a hydrogen-bond network extends throughout the crystal (N .. O 2.84 to 3.02 A) and involves all H atoms of the cation. Structures were solved from, respectively, diffractometer data (R 0.074 for 210 reflections) and photographic data (R 0.074 for 488 reflections). The cell parameters of (N2H6)(H2P02)2 are: P21/c, a = 7.74(1), b = 6.44(1), c = 6.77.(1) A, (3 = 98.1(1)°.


T J R WEAKLEY ,