Sodium dithiophosphate

Sodium dithiophosphate

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Identifiers
CAS Number	13721-37-4 Y
Properties
Chemical formula	Na3PS2O2
Molar mass	196.072 g mol−1
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium dithiophosphate is the salt with the formula Na₃PS₂O₂, although the solid is usually encountered as the hydrate. It is also supplied as an aqueous solution together with other thiophosphates. 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 of phosphorus pentasulfide to give dithiophosphate, which is isolated as its barium salt:

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

Applications

This salt is used as a flotation agent in molybdenite mineral concentration from ores, where it is usually known as "Nokes reagent." 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," since it suppresses the flotation tendency of the solids.

See also

• Diethyl dithiophosphoric acid
• Zinc dithiophosphate