Sodium dithiophosphate is the

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

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 chemical formula . It is a sodium salt of monothiophosphoric acid (). Sodium monothiophosphate forms hydrates . The anhydrous form and all hydrates are white s ...

and

sodium trithiophosphate Sodium is a chemical element; it has symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope i ...

. 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 (empirical) or ( molecular). 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 ...

: :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 of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

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 at ...

(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 . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...

, 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 chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thu ...

, 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