Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration

1.1 This test method covers procedures for the determination of acidic constituents in petroleum products and lubricants soluble or nearly soluble in mixtures of toluene and propan-2-ol (Note 1). It is applicable for the determination of acids whose dissociation constants in water are larger than 10-9; extremely weak acids whose dissociation constants are smaller than l0 -9 do not interfere. Salts react if their hydrolysis constants are larger than 10 -9 .