羟基在吡啶溶液中被醋酸酐酯化。多余的醋酸酐用水水解。酯化过程中出现的酸度和水解过程中形成的乙酸在酚酞作为指示剂的情况下用氢氧化钠溶液中和。羟基值是由用于滴定空白的氢氧化钠溶液和试验溶液的体积之间的差值来计算的。

The hydroxyl group is esterified by acetic anhydride in pyridine solution. The excess of acetic anhydride is hydrolized with water. The acidity which appears during the esterification and the acetic acid formed during the hydrolysis are neutralized by sodium hydroxide solution in the presence of phenolphthalein as indicator. The hydroxyl value is calculated from the difference between the volume od sodium hydroxide solution used for the titration of the blank and of the test solution.