Based on the cyanidine reaction, a quantitative electrocolorimetric method for the estimation of hesperidin is described. The main steps of the procedure are as follows:Extraction: The sample is washed successively with 95% alcohol and ether until the washings are free from yellow color when alkali is added. The washed sample is then extracted under re fluxing for 90 minutes with 50% alcohol (the best ratio between the sample and alcohol ia 1:100 by weight), filtered while hot, and the filtrates is kept at 70℃ until used.Color producing and comparison: Five ml of the above extract are added into a test tube containing 250 mg of magnesium powder. The tube thus prepared is placed into warm water of 15℃ and 2 ml of cone. HCl are added slowly (0.2 ml for every 2 minutes) with gentle shaking. After the addition of HC1 is completed, the content of the tube is shaken and incubated at 37℃ for 1 hour. The extract is then cooled, filtered and its optical density is determined. The error introduced by the colored sample solution is corrected by setting the optical density reading of the blank at zero before the reading of the unknown. The blank was prepared similarly as the unknown except that the reaction of magnesium powder with added HCl was completed before the addition of sample solution.The hesperidin content of the sample is determined by interpolation of the optical density values on a standard curve prepared by a series of gradient concentration of hesperidin.An amount of 0.025 mg hesperidin in 5 ml solution can be determined quantitatively by this method and the recovery was 97.1-100.3%.