This part of ISO 787 specifies a general method of test for determining the acidity or alkalinity of the aqueous extract of a Sample of Pigment or extender. NOTE - When this general method is applicable to a given Pigment or extender, only a Cross-reference to it should be included in the International Standard relating to that Pigment or extender, with a note of any detailed modification which may be needed in view of the special properties of the material in question. Only when this general method is not applicable to a particular material should a special method for determination of acidity or alkalinity be specified.