The principle of the method consists in weighing of a test portion and dispersing in a suitable volume of water. The dispersion is poured through a sieve. Washing of the test portion until the washings passing through the sieve are clear and free of dispersed material. Treatment of the residue on the sieve with water and drying in an oven at 105 °C 2 °C. Allow to cool and weigh to the nearest 1 mg. Alternative procedures for the treatment of residue: Washing of the residue into a previously heated and weighed sintered crucible, into a previously heated and weighed 50 ml beaker or into a previously heated and weighed weighing bottle. - Cancels and replaces ISO Recommendation R 787/7-1968.