Specifies a method for a visual comparison of the turbitity obtained by adding a barium chloride solution to a solution of a test portion acidified with hydrochloric acid, with that similarly obtained from a sulphate solution of known concentration. Using a test portion of 100 g, the method is applicable directly to products having inorganic sulphate contents in the range 0,001 % (m/m) to 0,1 % (m/m). This range can be extended by adjusting the mass of the test portion. It has also been approved by the International Union of Pure and Applied Chemistry (IUPAC). ISO 753/1 to ISO 753/11 cancel and replace ISO Recommendation R 753-1968.