Provides certain indications relating to the sampling and indicates the conditions under which the test sample should be prepared The special properties which make particular precautions essential such as hygroscopic characteristics, absorption of carbon dioxide, corrosive action on containers, should be stressed. The preparation of the main solution is carried out by dissolution of the test portion in distillated water or by transfer of the liquid test portion directly and quantitatively in a one-mark volumetric flask. Cancels and replaces ISO Recommendation R 988-1969 and ISO recommendation R 989-1969.