The crystal structure of the ice‐like form of sulphur trioxide (γ‐modification)

The crystal structure of the γ‐modification of sulphur trioxide has been completely determined. The cell is orthohombic, with cell constants a = 12.3 Å, b = 10.7 Å and c = 5.3 Å and contains 12 units of SO 3 ; the X‐ray density is 2.29. The structure is a molecule lattice built up of molecules S 3 O 9 ; a [001] projection is seen in fig. 7, the atomic positions are given on p. 806, 807. The molecule S 3 O 9 contains a puckered (SO) 3 ring (fig. 4b), in agreement with the latest results of Raman and infrared investigation.