Sodium Chlorite

NaClO2

IUPAC name: Sodium chlorate (III)
Other names: Sodium chlorite; chlorous acid sodium salt..
CAS number: 7758-19-2

Sodium chlorite is a sodium salt of chlorous acid and a powerful oxidant. It is more stable than sodium chlorate, and indeed it does not decompose by friction. The anhydrous salt is not hygroscopic and is stable over several years if properly stored. In a dry state, chlorites are stable at room temperature; they decompose violently when heated above 100 C.

Manufacture

The main compounds used to manufacture sodium chlorite are chlorine dioxide and sodium hydroxide.
The chlorine dioxide is made to bubble through a caustic soda solution, yielding sodium chlorite and sodium chlorate in approximately equal quantities. A reducing agent (hydrogen peroxide is used industrially) is utilised to decrease the production of sodium chlorate. The compound is purified by fractional crystallisation, taking advantage of the different solubility of the chlorate and chlorite. A product of very high purity is obtained by this method.

Principal uses

Sodium chlorite is utilised in many sectors.

    • Disinfection: water disinfectant to prevent microbial and bacterial growth, the formation of unpleasant odours (sodium chlorite slowly releases chlorine dioxide, a very reactive compound that allows the removal of iron and manganese ions, the oxidation of halogenated hydrocarbons, and, consequently, bad smells.)
    • Textile industry: as a textile bleaching agent, sodium chlorite reacts with many fibres. It can be utilised on cotton as well as on vegetable and synthetic fibres such as nylon, perlon, rhovyl, and dralon.
    • Paper industry: its oxidising action causes the destruction of pectins in the cellulose fibres, making them more soluble and pliable. It is also utilised to remove colour without attacking the fibres themselves.
    • It is also utilised:
      to produce chlorine dioxide in the laboratory; in the scrubbers, because it is a very strong oxidant; to wash fruits and vegetables, and as an anti-mould because of its fungicide action.