Abstract: Acid value is an important index to measure the quality and performance of lubricating oil products. The influence of single factors, such as titrating solvent, sample volume, titrating rate and titrating mode, on acid value determination of lubricating oil by potentiometric titration was discussed. In view of the existing problems, the response surface method was used to characterize the synergetic effect of each single influencing factor, screen the optimal test conditions, and avoid the influence of the improper selection of test conditions on the test results. The results showed that the predicted results by response surface method were basically consistent with the actual test results, which could optimize test conditions, shorten test time and reduce the number of test error.

Key words: potentiometric titration, lubricating oil, acid value, response surface methodology, influencing factors