A high-frequency microtitration method is described for the determination of total acid number in new and used lubricating oils. The sample, dissolved in tolueneethanol (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 a t 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.

The determination of total sulphur in naphthas and other volatile hydrocarbons is reported. The method developed involves the combustion of the sample in oxygen and conductimetric high-frequency micro-titration of the sulphate ions in the absorbing solution of hydrogen peroxide with standardised barium perchlorate solution. An aliquot is prepared by controlled evaporation to dryness (-0.5 ml) and then diluted with ethanolwater mixture (3 + 2). The method has been established for samples containing 0.4-50 p.p.m, mlm of sulphur.