The influence of temperature and storage time of polymeric sulfur from different producers on its behaviour in rubber compounds was studied. Also, the influence of activation by neutron irradiation on a quantity of an insoluble fraction in polymeric sulfur was investigated. To better understand the reason of the small difference in properties of tested polymeric sulfur, its topological structures were evaluated using a thermomechanical method. It was confirmed by a previous conclusion that these kinds of polymeric sulfur have very similar topological structure, and as a result, their behavior in rubber compounds should be practically the same. Studying the reason of blooming in the mineral sulfur it was found that at normal storage conditions, sublimation and oxidative degradation of soluble sulfur could be negligible. For these measurements radioisotopic methods were used.