This standard applies to all types of water (both filtered and unfiltered) with a potassium permanganate consumption of at least 1.5 mg/l. The volume of water to be processed (see 7) may not contain more than 100 mg chloride (Cl") (see also Appendix A). Interference due to iron(ll), sulfide, sulfite and nitrite is prevented by oxidation and boiling with sulfuric acid. Note If the chloride content is too high, the method described in Annex B can be followed. This alkaline method is not affected by chloride but gives results that are not comparable to those of the actual standard
NEN 6491-1984 history
1984NEN 6491-1984 Water - Titrimetric determination of the potassium permanganate demand and/or permanganate index