High-frequency microtitrimetric determination of acidic and basic constituents in lubricating oils. Part 1. Determination of total acid number

Abstract

A high-frequency microtitration method is described for the determination of total acid number in new and used lubricating oils. The sample, dissolved in toluene-ethanol (7 + 3), is titrated with standard alcoholic tetramethylammonium hydroxide solution. A study of solvents, titrants, sample size and other experimental parameters is reported. This method provides sharp breaks at the end-point and more repeatable results faster than those obtained with the standard potentiometric method. The method can be expanded to the macro-scale using a commercially available titrator and offers an alternative to the ASTM and IP methods for the determination of total acid number.