This International Standard specifies a method for the determination of basic constituents in petroleum products by potentiometric titration with perchloric acid in glacial acetic acid. The constituents that may be considered to have basic characteristics include organic and inorganic bases, amino compounds, salts of weak acids (for example soaps), basic salts of polyacid bases, and salts of heavy metals. Two variations of the method are described, Procedures A and B, using different titration solvent volumes and test sample masses.