1.1 This International Standard specifies the methods to be used for the evaluation of natural calcium carbonate (chalk or limestone) ground to a dry powder for use in the rubber industry. NOTE 1 Classification of natural calcium carbonate according to fineness and chemical purity and typical physical and chemical properties for use in the rubber industry are given in informative annex D. NOTE 2 This International Standard does not cover calcium carbonates prepared by precipitation from solution. 1.2 There are two sets of analytical methods listed in this International Standard. In the body of the text (4.8.2 to 4.8.4), the traditional spectrophotometric methods are given; these are obsolescent, time-consuming and use a chlorinated solvent. It is recommended that these methods be phased out and replaced by the atomic absorption methods listed in annexes A, B and C.