Sodium hypophosphite (NaPO₂H₂, also known as sodium phosphinate) is the sodium salt of

hypophosphorous acid Hypophosphorous acid (HPA), or phosphinic acid, is a phosphorus oxyacid and a powerful reducing agent with molecular formula H3PO2. It is a colorless low-melting compound, which is soluble in water, dioxane and alcohols. The formula for this ...

and is often encountered as the monohydrate, NaPO₂H₂·H₂O. It is a solid at room temperature, appearing as odorless white crystals. It is soluble in water, and easily absorbs moisture from the air. Sodium hypophosphite should be kept in a cool, dry place, isolated from oxidizing materials. It decomposes into

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

which is irritating to the respiratory tract and

disodium phosphate Disodium phosphate (DSP), or disodium hydrogen phosphate, or sodium phosphate dibasic, is the inorganic compound with the formula Na2HPO4. It is one of several sodium phosphates. The salt is known in anhydrous form as well as forms with 2, 7, 8, ...

. :2 NaH₂PO₂ → PH₃ + Na₂HPO₄

Uses

Like other hypophosphites, sodium hypophosphite can reduce metal ions back into base metal. This forms the basis for

electroless nickel plating Electroless nickel-phosphorus plating is a chemical process that deposits an even layer of nickel-phosphorus alloy on the surface of a solid substrate, like metal or plastic. The process involves dipping the substrate in a water solution containi ...

(Ni-P), which is its main industrial application. With this method, a durable nickel-phosphorus film can coat objects with irregular surfaces, such as in avionics, aviation and the petroleum field. Sodium hypophosphite is capable of reducing nickel ions in solution to metallic nickel on metal substrates as well as on plastic substrates.D. Rich & M. Smith, Electroless Deposition of Nickel, Cobalt and Iron, IBM Corp (1971) The latter requires that the substrate is activated with fine particles of palladium. The resulting nickel deposit contains up to 15% phosphorus. It has been investigated as a

food additive Food additives are substances added to food to preserve Taste, flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), sal ...

DEA List I status

The United States

Drug Enforcement Administration The Drug Enforcement Administration (DEA; ) is a United States federal law enforcement agency under the U.S. Department of Justice tasked with combating drug trafficking and distribution within the U.S. It is the lead agency for domestic en ...

designated sodium hypophosphite as a List I chemical under 21 CFR 1310.02 effective November 17, 2001, specifically mentioning the compound together with several other salts of hypophosphorous acid.66 FR 52670—52675.
17 October 2001.
/ref>

References

{{Sodium compounds Sodium compounds Phosphinates Inorganic phosphorus compounds Reducing agents