Abstract
The use of sodium hydrosulfide and Na_2HPO_4,respectively, for removing lead after lead salt treatment gave similary good results for the determination of niacin content of foodstuffs. The blank values were however usually higher in the case of phosphate. For assaying the vitamin in vegetable tissues the use of H_2SO_4 rather than HCl is generally preferrable, because the filtrate gave less color due to non-vitamin impurities. The hydrolysis with NaOH was often proved to be unsuitable in the case of vegetable tissues owing to the coloration due to impurities. In some samples it was shown to be necessary to make blank tests for bromide correction as well as color correction in addition to that for amine correction. The contents of niacin in the blood of Japanese were found generally to be somewhat higher than the values hitherto reported even after the above corrections.
