AbstractThree new structural phase transformations in the Cs amidosulfonate were detected and studied by means of DSC, X‐ray diffraction, infrared spectroscopy and by measuring the temperature dependence of the dielectric constant of monocrystalline platelets. In the temperature range from 325 to 345 K a second‐order phase transition occurs. After completion of the second order‐phase transformation, a first‐order phase transformation proceeds. At higher temperatures (435 K) a lambda‐transition occurs. The transition temperatures, enthalpies and entropies of the above reactions as well the melting temperature and the heat of melting of the CsSO3NH2were obtained. By means of the methods of H. KISSINGER and T. OZAWA the activation energies of the first order phase transformation were d