Abstract
Oxidation of thiamine by alkaline ferricyanide solution always yielded thiochrome and thiamine disulfide (TDS) in different proportions according to pH of the reaction-media. 0.2% solutions of thiamine were first adjusted to different pH between 8.7 and 13.1 by buffers and immediately followed by addition of ferricyanide and after standing for 0〜30 minutes, aliquot portions from the solutions were separately taken to determine TDS by thiochrome method with cysteine-reduction after adsorption to Amberlite IRC-50 column. The formation of TDS was most favorable at pH 11.6 (Fig.1). If the thiamine solutions were kept for standing still more than 5 minutes at pH 11.6 before the addition of ferricyanide, yields of TDS were nearly quantitative but at pH lower than 11 or higher than 12,formation of TDS was decreasing. Oxidation of thiamine or its derivatives at pH 11〜12 in higher concentraions gave better yields and purer crystals of TDS or its derivatives than other preparative procedures using alkaline iodine or hydrogen peroxide. The formation of thiochrome was highest at pH 13.1 but it decreased so rapidly to increase the yield of TDS predominantly, by standing the strongly alkaline thiamine solution for a while before the addition of ferricyanide.
