ASTM D2896 - Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration

Significance and Use

5.1 New and used petroleum products can contain basic constituents that are present as additives. The relative amounts of these materials can be determined by titration with acids. The base number is a measure of the amount of basic substance in the oil, always under the conditions of the test. It is sometimes used as a measure of lubricant degradation in service; however, any condemning limits must be empirically established.

1. Scope

1.1 This test method covers the determination of basic constituents in petroleum products by titration with perchloric acid in glacial acetic acid.

1.2 Procedures A and B use different titration solvent volumes and sample weights.

NOTE 1: A round robin on a series of new and used oils and additive concentrates has shown that the two procedures give statistically equivalent results.

1.3 Appendix X2 provides the use of an alternative solvent system which eliminates the use of chlorobenzene in this test method. The use of the alternative solvent gives statistically equivalent results; however, the precision is worse. Paragraph X2.5.5 provides guidance when comparing results using the two different solvents.

1.4 The constituents that may be considered to have basic characteristics include organic and inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of polyacidic bases, and salts of heavy metals.

NOTE 2: This test method is applicable to both fresh oils and used oils as described in Sections 16, 17, and 19 and Appendix X1.

1.5 This test method can be used to determine base number >300 mg KOH/g. However, the precision statement in Section 19 has been obtained only on base number ≤300 mg KOH/g.

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

Extracted, with permission, from ASTM D2896-21 - Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be purchased from ASTM International, astm.org