1. Pseudo-dihydrothiamine was found to possess hydroxyl and imino groups from the infrared absorption spectrum. 2. Normal-, iso-, and pseudo-dihydrothiamines give the same benzoyl-pseudo-dihydrothiamine. 3. It was concluded from foregoing results that pseudo-dihydrothiamine possessed a structure entirely different from that of normal- and iso-dihydrothiamine.
