text: This salt is used as a flotation agent in the purification of molybdenite (MoS) from other components of the ores, where it is usually known as "Nokes reagent" (after Charles M. Nokes, who patented it in 1948).  The salt is generated by the reaction of phosphorus pentasulfide with sodium hydroxide, often using impure reagents to obtain a mixture of the desired salt and related thiophosphates and oxidized species.  Molybdenite particles, which are normally hydrophobic, become hydrophilic in the presence of this salt.  In this context, the Nokes reagent is called a "depressant," because it suppresses the flotation tendency of the solids other than molybdenite.