 In water chlorination, sodium bisulfite is used to reduce the residual 'chlorine' which can have a negative impact on aquatic life.In organic chemistry, "sodium bisulfite" is a routine reagent but its composition is imprecisely known.Sodium bisulfite is used interchangeable with sodium metabisulfite, which is Na2S2O5 as a solid but dissolves to give a solution of Na+HSO3-.