Sodium dithiophosphate is the

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

with the formula Na₃PS₂O₂. It is usually supplied as the hydrated solid or as an aqueous solution together with other

thiophosphate Thiophosphates (or phosphorothioates, PS) are chemical compounds and anions with the general chemical formula (''x'' = 0, 1, 2, or 3) and related derivatives where organic groups are attached to one or more O or S. Thiophosphates feature tetrahedr ...

s such as

sodium monothiophosphate Sodium monothiophosphate, or sodium phosphorothioate, is an inorganic compound with the molecular formula Na3PO3S(H2O)x. All are white solids. The anhydrous material (x = 0) decomposes without melting at 120-125 °C. More common is the dode ...

and sodium trithiophosphate. It is a colorless compound, but commercial samples can appear dark owing to the presence of impurities. It is used to facilitate the isolation of molybdenum from its ores.

Preparation

The compound has been prepared in a multistep process starting with the

base hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysi ...

phosphorus pentasulfide Phosphorus pentasulfide is the inorganic compound with the formula (monomer) or (dimer). This yellow solid is the one of two phosphorus sulfides of commercial value. Samples often appear greenish-gray due to impurities. It is soluble in carbon d ...

: :P₂S₅ + 6 NaOH → 2 Na₃PO₂S₂ + H₂S + 2 H₂O The salt is isolated as the hydrate Na₃PO₂S₂^.(H₂O)₁₁. It is prone to hydrolysis, especially when it is heated as an aqueous solutions: :Na₃PO₂S₂ + 2 H₂O → Na₃PO₃S + H₂S Its structure has been examined by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

Applications

This salt is used as a flotation agent in the purification of

molybdenite Molybdenite is a mineral of molybdenum disulfide, Mo S2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum ato ...

(MoS₂) 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

with

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...

, often using impure reagents to obtain a mixture of the desired salt and related thiophosphates and oxidized species. Molybdenite particles, which are normally

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...

, 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.

References

Phosphorothioates Sulfides Sodium compounds Metallurgical processes {{inorganic-compound-stub

Preparation

Applications

See also

References