Sodium dithiophosphate

Sodium dithiophosphate is the salt with the formula Na₃PS₂O₂. It is usually supplied as the hydrated solid or as an aqueous solution together with other thiophosphates such as sodium monothiophosphate 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.

Sodium dithiophosphate

Identifiers
CAS Number	13721-37-4 Y
3D model (JSmol)	Interactive image monohydrate: Interactive image
ChemSpider	monohydrate: 32818081
PubChem CID	20430759 monohydrate: 118856075
InChI InChI=1S/3Na.H3O2PS2/c;;;1-3(2,4)5/h;;;(H3,1,2,4,5)/q3*+1;/p-3 Key: OFLNOEMLSXBOFY-UHFFFAOYSA-K monohydrate: InChI=1S/3Na.H3O2PS2.H2O/c;;;1-3(2,4)5;/h;;;(H3,1,2,4,5);1H2/q3*+1;;/p-3 Key: ZBHVOFQECIYLFG-UHFFFAOYSA-K
SMILES [O-]P(=S)([O-])[S-].[Na+].[Na+].[Na+] monohydrate: O.[O-]P(=S)([O-])[S-].[Na+].[Na+].[Na+]
Properties
Chemical formula	Na3PS2O2
Molar mass	196.072 g mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation

The compound has been prepared in a multistep process starting with the base hydrolysis of phosphorus pentasulfide:^[1]

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.^[2][3]

Applications

This salt is used as a flotation agent in the purification of molybdenite (MoS₂) from other components of the ores, where it is usually known as "Nokes reagent" (after Charles M. Nokes, who patented it in 1948^[4]). 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.^[5][6]

See also

• Diethyl dithiophosphoric acid
• Zinc dithiophosphate