The principle consists in reaction of a test portion, under specified conditions, with an excess of potassium permanganate solution in the presence of dilute sulphuric acid. Iodometric titration of the residual potassium permanganate. The method is applicable to products having permanganate indexes equal to or greater than 10 mg/100 ml. It has also been approved by the International Union of Pure and Applied Chemistry (IUPAC). ISO 753/1 to ISO 753/11 cacel and replace ISO Recommendation R 753-1968.