本方法用于通过电位滴定法测定石油产品、石油馏分和类似材料的酸值。无机酸、有机酸、硫醇和硫酚对该分析有反应，但它们各自的盐对该分析没有反应。对于环烷酸，通常需要在测量中包括盐。因此，还包括测定环烷酸钠盐的程序。酸值测定的典型范围为0.002至5 mg KOH/g样品，尽管可以容纳更高的浓度。该方法包括三个步骤。样品的酸值可以根据收到的样品或不含硫醇和硫酚的样品进行测定。该方法也可用于测定碱洗碳氢化合物中的环烷酸，包括环烷酸钠（肥皂）。对于130的估计相对分子质量，环烷酸的定量范围为5至500质量- ppm。后两种程序几乎完全适用于轻质煤油和柴油，其中假定有机酸完全是环烷酸。如果没有电位滴定仪，且样品颜色较浅，则可采用比色法进行滴定；见附录。

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.There are three procedures included in the method. The acid number of a sample can be determined on an as-received basis or on a mercaptan- and thiophenol-free basis. The method can also be used to determine naphthenic acids including sodium naphthenates (soaps) in caustic-washed hydrocarbons. For an estimated relative molecular mass of 130, the range of quantitation for naphthenic acids is 5 to 500 mass-ppm. The latter two procedures apply almost exclusively to light kerosines and gas oils where it is assumed that the organic acids are entirely naphthenic.If no potentiometric titrator is available, and the sample is light in color, the titration may be performed colorimetrically; see the APPENDIX.