ISO 1389-9:1977

Phthalic anhydride for industrial use — Methods of test — Part 9: Determination of impurities oxidizable in the cold by potassium permanganate — Iodometric method

This method is not specific for maleic anhydride. The polarographic method specified in part 7 should be used. The principle is based on the oxidation of unsaturated organic acids and anhydrides in a test portion with an excess of cold standard volumetric potassium permanganate solution in the presence of sulphuric acid, followed by iodometric determination of the potassium permanganate remaining. – ISO 1389, Parts 1 to 11, replace ISO Recommendation R 1389-1970.