The oxidation of phosphorus by sulfur at low temperatures (<100 degrees C) has been shown to produce complex mixtures that include 12 of the 17 known binary phosphorus sulfides. Two of these 17 sulfides have been observed in these mixtures for the first time, The rate-determining and first step in the reaction appears to be the formation of the Ss diradical, This proposal is supported by the observed rate at which the sulfides are formed and the distribution of the sulfide product stoichiometries. Photoinitiation of this oxidation at O degrees C produces a similar array of sulfides, The differences in the product distributions between the thermal and photochemical processes facilitate the understanding of the mother-daughter relationships between the products. The effects of oxidation by sulfur and reduction by phosphorus have been determined for several of the known phosphorus sulfides. The characterizations of phosphorus compounds in molten mixtures of phosphorus and sulfur were performed by P-31 NMR and Raman spectroscopy directly on the reaction mixtures.