Differential scanning calorimetry (DSC) and X-ray diffraction measurements have been performed on cesium sulfamate CsNH 2 SO 3 single crystal. Two distinct endothermic peaks in the DSC curves are observed at 330 and 436 K. It is pointed out that the peak at 330 K is attributed to the structural phase transition, and the other peak at 436 K is associated with the thermal decomposition of the crystal. The structures in room-and hightemperasture phases are determined, and the space group of the sample crystal is found to change from monoclinic P2 1 /c to orthorhombic Pnma. The structure of the room-temperature phase consists of two different types of N-H···O hydrogen bond, but in the high-temperature phase there is no specific hydrogen bond between the NSO 3 pseudo-tetrahera.

Crystal Structure and Phase Transition of Single Crystalline CsNH 2 SO 3 . -Single crystals of the title compound are prepared at room temperature by slow evaporation of aqueous solutions containing stoichiometric amounts of Cs 2 CO 3 and NH 2 SO 3 H. CsNH 2 SO 3 crystallizes in the monoclinic space group P2 1 /c with Z = 4 at 297 K and in the orthorhombic space group Pnma with Z = 4 at 352 K. The phase transition occurs at 330 K. The structure of the room-temperature phase contains CsX 9 (X: O,N) polyhedra, whereas the high-temperature structure contains CsX 8 polyhedra. There are two different types of N-H···O hydrogen bonds in the room-temperature phase and no hydrogen bond in the high-temperature phase. The crystal decomposes at 436 K. -(FUKAMI*, T.; KYAN, T.; NAKANO, K.; CHEN, R. H.; Cryst. Res. Technol. 46 (2011) 3, 287-291, http://dx.doi.org/10.1002/crat.201000623 ; Dep. Phys. Earth Sci., Fac. Sci., Univ. Ryukyus, Okinawa 903-02, Japan; Eng.) -W. Pewestorf 22-002