This standard describes sodium chlorite, in either solid (granular, flake, or powdered) or aqueous-solution form, for use in making chlorine dioxide for use in the treatment of potable water, wastewater, and reclaimed water. Sodium chlorite must be packaged, labeled, and registered according to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) as administered by the US Environmental Protection Agency (USEPA). State regulations may also apply. This standard can be referenced in documents for purchasing and receiving sodium chlorite and can be used as a guide for testing the physical and chemical properties of sodium chlorite samples. The stipulations of this standard apply when this document has been referenced and then only to sodium chlorite used in the treatment of potable water, wastewater, and reclaimed water.