Titrimetric determination with addition of iodine solution and reverse titration of unused iodine with sodium thiosulphate.
Larger concentrations of sulphide and nitrite ions interfere.
The method can be used for the analysis of sea water.
For determination of dithionite (hydrosulphite) please ask for our special instruction.
(Reaction principle analogous to APHA 4500-SO₃^2- B)

Sulphite ions are not present in natural unpolluted waters, however they often appear in large quantities in industrial waste waters (e. g. paper mills, dye works).