Describes a method for the determination of the esterrified acid content in raw materials for coating materials whereby free acids and acid anhydrides are necessarily included. The method is not applicable to those mnaterials which show further reaction with alkalis beyond normal saponification. The principle consists in dissolving the test portion in a measured volume of a unsaponifiable solvent, addition of a specified or agreed volume of a potassium hydroxide solution. Heating of the contents of the flask to boiling under reflux for 1 h or as specified, titration of the hot solution with standard volumetric hydrochloric acid solution acid solution against phenolphthalein as indicator.