Once the constitution and chemical nature of vitamin C (cevitamic acid) were established, it became possible to develop strictly chemical methods for determining this dietary essential in food materials, tissues and body fluids. The most widely used method employs the readily reduced organic compound 2,6 dichlorophenol indophenol as an indicator; the specificity of the reaction as well as the comparison of the results so obtained with the time-consuming bio-assay on guinea-pigs has received careful attention. The wide usefulness of the titration method has been demonstrated. Thus, not only is it possible to note changes in the vitamin C content of foods as a result of processing— cooking, pasteurization, storage—but the localization of cevitamic acid in certain animal tissues and the variations in its concentration in blood and urine can be determined in a relatively short time.
That the content of this dietary essential in the plasma parallels its content in