The Chemistry of the Lipids of Tubercle Bacilli Exev. the Constitution of Phthiocol, Thie Pigment Isolated from the Human Twercle

In Paper XXXIV of this series (1) we described the isolation of a pigment from the ether-soluble constituents obtained on saponification of the acetone-soluble fat. The present report deals with the determination of the chemical constitution of the pigment. In order to indicate its origin, we propose to designat,e the pigment by the name phthiocol. Phthiocol crystallizes in yellow prisms which melt at 173-174”. It is volatile with steam and soluble in all common organic solvents except petroleum ether. It forms deep red, water-soluble salts with alkalies and other bases. In fact, a red color develops so easily in the presence of alkali that the heated portions of the melting point tubes become red as do also filter papers after filtering solutions of phthiocol. The elementary composition of phthiocol agrees with the formula CnH808. On direct acetylation a light yellow monoacetate is obtained and this compound, on reductive acetylation by refluxing with zinc dust and acetic anhydride, is converted into a colorless triacetate. This indicates a quinone linkage in the original substance and thus the 3 atoms of oxygen are accounted for, 1