THE CHEMICAL ASSAY OF CHINESE LIQUORICE ROOT

1. A brief review of the assay processes of liquorice root is made. 2. After investigating the more important stages in the processes of Houseman and Fahmy, the following improvements are made to obtain a more complete separation of glycyrrhizic acid: (1) duration for the precipitation of glycyrrhizic acid is prolonged from 2 1/2 hours employed by Houseman to 24 hours; (2) concentration of the sulphuric acid usad for the precipitation of glycyrrhizic acid is changed from 0.3 per cent employed by Houseman to 1.4 per cent; (3) temperature for the precipitation of glycyrrhizic acid is lowered from room temperature employed by Fahmy to 6-7°C. 3. Benedict's quantitative solution is used in place of Fehling's solution in the titration of reducing sugars, because the former solution is more stable and has better keeping properties. 4. An improved process for the assay of liquorice root is described. Five samples of Chinese liquorice root have been assayed by this method. The results obtained are as follows: water-soluble extractives, 26.17—35.59 per cent; glycyrrhizic acid 5.49—10.04 per cent; total reducing sugars, 4.70—10.97 per cent; starch and gummy matter, 4.17—5.92 per cent; water, 8.04—8.93 per cent; ash, 3.06—4.24 per cent; acid-insoluble ash, 0.25—0.65 per cent. The above results showed that the samples assayed fully conform with the requirements of the pharmacopoeias of most countries.