The paths to the discovery of vitamins A and D.

The previous work reported from this laboratory on the chemical nature of vitamin C has been continued, particularly in the study of the solubility of the active material in organic solvents, leading towards its isolation by crystallization. This paper deals with (a) the precipitation of the active material as the lead salt, and (b) the isolation of a crystalline compound which is active in preventing scurvy in guinea pigs. The properties of this active crystalline substance correspond with those given for the "hexuronic acid" studied by Szent-Györgyi as an oxidation-reduction factor in adrenal cortex, oranges, and cabbage. We believe that the two substances are identical, as stated in a previous communication.