Synthesis and complete structural characterization by X-ray diffraction, DTA, GTA and IR are given for a new cyclohexaphosphate: (1,6-NH 3 C 6 H 1 2 NH 3 ) 2 (1-NH 3 C 1 0 H 7 ) 2 P 6 O 1 8 .2H 2 O. This compound is monoclinic P2 1 /c with the following unit-cell parameters: a = 11.861(2) 9, b = 10.104(1) 9, c = 19.664(6) 9, β = 96.44(2) o , and Z = 2. The crystal structure has been solved and refined to R = 0.033 using 3928 independent reflections. The atomic arrangement can be described as layer organisation. Layers built by P 6 O 1 8 ring anions and water molecules spread in the plans (100). Between these layers are located the organic groups which form hydrogen bonds with oxygen atoms of P 6 O 1 8 rings and water molecules. Geometrical characteristics of hydrogen bonds are described. The reported IR study is supported by a delaited theoretical group analysis applied to P 6 O 1 8 with D 6 h ideal local symmetry.