ISO 787-4:1981 "General test methods for pigments and fillers, Part 4: Determination of acidity or alkalinity of aqueous extracts" specifies a general method for the determination of acidity or alkalinity of aqueous extracts of pigments or fillers. This standard aims to provide a uniform test method for the performance evaluation of pigments and fillers, ensuring conformity and Reliability of the test results. Chemical Stability and Suitability of a sample can be assessed by determining the acidic or alkaline reaction produced during water extraction. This method is suitable for a wide range of pigments and fillers and cross-referenced guidance is provided in international standards for appropriate adjustments and modifications in practical applications.