Abstract
By an alkaline ferricyanide solution, thiamine was oxidized into thiochrome and thiamine disulfide in different proportions which were variable according to pH of the solution. Moreover, dissolved oxygen in the solution gave a considerable influence to stimulate formation of thiamine disulfide and inhibit oxidation to thiochrome. But at pH between 11-12 formation of thiamine disulfide was predominant even at the exclusion of oxygen by saturating N_2 in the solution. At pH over 13,formation of thiochrome from 10μg thiamine was 83% to the theoretical value in the N_2-saturated solution and 58% in the O_2-saturated solution. If the O_2-saturated solution of thiamine was replaced by N_2,the yield of thiochrome was recovered as high as that of the initially N_2-saturated solution. Dissolved oxygen or its exclusion by N_2-saturation gave no influence to the absorption at 340mμ of an alkaline thiamine solution. So an assumed intermediate showing absorption at 340mμ would not be a key substance to formation of thiochrome, however dissolved oxygen will push the reaction to form thiamine disulfide and exclusion of oxygen makes it favorable to form thiochrome.
