Potentiometric titration test method for acid value of esterified esters

The invention relates to a potentiometric titration test method of acid value in an ester, which is characterized in that (1) 0.2500g plus or minus 0.0001g of sample powder is precisely weighted and placed into a 250ml ground conical flask, 50ml of N and N-dimethyl formamide is added, the heating on an electric furnace is carried out for 15 minutes for the dissolution, then the mixture is cooled to the room temperature and is fully transferred into a 100ml beaker in tall form, and 3 or 4 drops of phenolphthalein indicator are added; (2) the method TAN of the acid value of the ester is selected on a potentiometric titrimeter, 0.05mol/L of KOH and CH3OH standard solution is used for titrating till the potential transition point that is the finish point, a blank test is carried out under the same conditions, and the acid value is calculated by a formula, thus having comparatively small error and high accuracy.