Process for making phosphorus pentasulfide

In a process for making phosphorus pentasulfide, wherein a phosphorus melt and a sulfur melt are introduced through separate feed pipes from storage vessels into a reactor, reacted therein under nitrogen at temperatures between 300.degree. C. and 400.degree. C., and the resulting phosphorus pentasulfide melt is taken from the reactor through a discharge pipe and delivered to a cooling means, the improvement which comprises:

• introducing gaseous nitrogen into at least one of the said feed pipes for the phosphorus and the sulfur running to the reactor, and into the reactor discharge pipe for the phosphorus pentasulfide melt, the nitrogen being introduced into the pipes at a level lower than the liquids level of the melts in the respective storage vessels or in the reactor and under a pressure lower than the static pressure exerted in the pipes by the quantity of melt upstream of the gas inlets.