scope:

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.

NOTE 1 Round-robin tests on a series of unused and used oils and additive concentrates have shown the Procedures A and B to give statistically equivalent results.

The ranges of base number values for which precision values for the method have been established are:

unused oils - base numbers from 6 to 70;

additive concentrates - base numbers from 5 to 300;

used oils on which were employed the forward titration - base numbers from 5 to 27.

NOTE 2 During the development of the original test method (Procedure A) and the test method using reduced titration solvent volume (Procedure B), cooperative testing was done on samples covering a wide range of types of oils, of additive concentrates which are used to prepare these oils, and of service conditions of the oils. Nevertheless it was not possible to cover the complete range of base numbers. It is reasonable to suppose that interpolation within and extrapolation, from the ranges actually tested will not introduce serious errors in the precision.