Abstract
The oxidation of vitamin B_<12> with hydrogenperoxide and hydrochloric acid was applied to the estimation of the so-called alkali stable factor in the bioassay of vitamin B_<12> using Lactobacillus leichmannii. The true vitamin B_<12> value might be obtained from the difference between the apparent vitamin B_<12> value and the activity remaininng after the treatment, since vitamin B_<12> is destroyed by the oxidation according to Beiler, while the alkali stable factor is left unchanged by the treatment. Sodium chloride produced in the treatment was found to exert no toxic effect on Lactobacillus leichmannii within the range of the determination. The satisfactory results were obtained also with several natural materials.
