Purification and Analysis of Bilirubin.

Pure crystalline bilirubin was isolated from human, calf, hog, and dog gallbladder bile and compared with commercially-available materials. All may be purified by recrystallization from pyridine. The extinction coefficient in chloroform is 60,000-61,000 at 450-453 mit. Standardization of the analytical “azobilirubin” (van den Bergh) reaction may be based on aqueous alkaline solutions of bilirubin. Paper chromatography of azobilirubins derived from various sources of bilirubin showed identical patterns.