It is recently said that the chemical determination of vitamin C content of plant and animal tissues must be carried out after the separation of the interfering reducing substance like glutathione, ferous salts, cystein, ergothioneine etc. Emmerie and Eekelen have modified the titration technique against the indicator 2, 6 Dichlorophenolindophenol to take place in acid medium after the treatment by mercuric acetate or barium acetate, because the substances like glutathione and ferrous salts dose not interfere in acid medium, and cysteine, ergothioneine can be precipitated by mercuric acetate or barium acetate, whereas the vitamin does not precipitated but remains in solution in the reversibly oxidised state. The author have observed the reducing capacity of certain plant tissues obtained in the following three cases, depending on the titration against 2, 6 Dichlorophenolindophenol. (1) determination in trichloracetic acid solution before the precipitation. (2) determ. in trichloracetic acid solution after mercuric acetate pfecipitation. (3) determ. in trichloracetic acid solution after barium acetate precipitation. It was led to the result, (1)>(3)>(2) and was found that a qualitative and quantitative difference between the precipitate by mercuric acetate and barium acetate. Secondly, the author have tested biologically on the solution treated with mercuric acetate or barium acetate precipitation, and reached to the result that the solution has antiscorbutic activity. Lastly, analysing urine, the urinary output of vitamin C in normal human subject is about 20mg. daily and it varies with the dietary intake of fruits and vegetable.