Dibromothymol-sulfonphathalein process for detecting acid value of oil

The present invention is assaying analysis method of determining acid value of oil and is especially Dibromothymol-sulfonphathalein process. The acid components in sample are extracted with ethanol and titrated with standard ethanol solution of potassium hydroxide. The indicator has color changing area of pH 6.0-7.6, is sensitive in the titration inside oil and water solution and the color changes from yellow to verdurous in the end point of titration. The indicator has stable chemical property in different weather condition, and the present invention has short test period, low cost, simple analysis process, high experiment precision and good data repeatability.