Under controlled conditions cobyric acid is obtained directly (10%) by the action of concentrated hydrochloric acid on vitamin B₁₂. The hydrolysis is complicated not only by the expected formation of other corrinoids of the normal series, but also by the formation of a second series of compounds which are darker than the normal derivatives, and which are related to Factor Ia. Cobinamide and Factor Ia may conveniently be obtained by the action of trifluoroacetic acid upon vitamin B₁₂.