This International Standard specifies the reference method for the determination of the fat content of liquid skimmed milk, whey and buttermilk. It is a particularly accurate gravimetric method especially for the purpose of establishing the operating efficiency of cream separators. This International Standard also specifies the reference method for establishing correction tables for procedures with skimmed milk butyrometers. NOTE When a high accuracy of determination is not required, the method specified in ISO 1211.IDF 1[2] is suitable.