This method is for determining the acid number of petroleum products, petroleum distillates, and
similar materials by potentiometric titration. Inorganic acids, organic acids, mercaptans and
thiophenols respond to this analysis, but their respective salts do not. For naphthenic acids, it is frequently desired to include the salts in the measurement. Therefore, a procedure is also included for the determination of sodium naphthenate salts. The typical range for acid number determination is 0.002 to 5 mg KOH/g of sample, although higher concentrations can be accommodated.