Abstract: Phosphorus pentasulfide of low reactivity is made by solidifying molten phosphorus pentasulfide on a cooling cylinder that delivers the solidified product at a temperature of 150.degree. to 220.degree. C., and that product is immediately introduced into a heat-insulated container and freed therein from its immanent or sensible heat by cooling at a rate of at most 30.degree. C. per hour without the expenditure of any energy to control the cooling.

Abstract: The invention relates to an apparatus for making P.sub.2 S.sub.5 comprised of a plurality of reactors connected by pipe structures to a collecting tank which is common to all of them. By means of partitions, the cooling tank is subdivided into a plurality of separate chambers. Outlet pipes open thereinto and terminate in collecting devices. The pipe structures running to the collecting tank are pivotably arranged above the various chambers and permit liquid P.sub.2 S.sub.5 to be introduced thereinto at will.

Abstract: The invention provides a process wherein a mixture prepared from starting materials comprised of P.sub.2 S.sub.5 of high reactivity and low reactivity, respectively, is converted to phosphorus pentasulfide of predetermined reactivity lying between that of the high reactivity P.sub.2 S.sub.5 and that of the low reactivity P.sub.2 S.sub.5 starting materials. To this end, the starting materials are mixed in quantitative proportions which are selected in accordance with the respective reactivity of the starting materials and the resulting mixture is ground.