CAROTIN, THE PRINCIPAL YELLOW PIGMENT OF MILK FAT 429 



in carbon bisulphide and alcohol, the solution in the first solvent 

 showing three distinct bands. This shows that the lipochrome which 

 Krukenberg extracted from ox serum was the pigment which we 

 have identified as carotin. On addition of alcohol to the other mixtures 

 the solvents in each case completely extracted the pigment on shaking. 



2. Five c.c. portions were dessicated with plaster of Paris and 

 shaken with ether, petroleum ether, and carbon bisulphide, respectively. 

 A mere trace of color was extracted in each case. When a little 

 absolute alcohol was added however, in all cases the solvents became 

 well colored. 



3. Five c.c. of serum was diluted with twenty volumes of water, 

 without causing any precipitation of the pigment. 



4. Twenty-five c.c. of serum was treated with successive por- 

 tions of saturated (NH 4 ) 2 SO 4 solution to the following per cent 

 saturations : 28-35, 36-40, 45-46, and finally to one-half saturation. The 

 fractionally precipitated globulins were in every case practically free 

 from carotin, and the half saturated globulin free serum was golden- 

 yellow. The color was entirely precipitated from a portion of this 

 solution on complete saturation with (NH 4 ) 2 SO 4 . The remainder 

 was acidified with a few drops of i^ per cent acetic acid and heated 

 to about 80 C. The coagulated albumins carried down only a small 

 part of the color. The entire pigment was precipitated from the 

 filtrate, however, on complete saturation with (NH 4 ) 2 SO 4 in sub- 

 stance, the light precipitate which came down being deep yellow in 

 color. This deep yellow precipitate was readily soluble in water 

 giving a clear yellow aqueous solution from which neither ether nor 

 petroleum ether would extract any color until the protein in the solu- 

 tion had first been coagulated with alcohol. 



5. Five c.c. of serum was diluted to 25 c.c. with distilled water 

 and the solution saturated with Mg SO 4 in substance. The globulins 

 were filtered off. The filtrate was golden-yellow. Acetic acid was added 

 to a concentration of I per cent. The precipitated albumins were 

 bright yellow, leaving the solution colorless. Petroleum ether and 

 carbon bisulphide extracted a slight amount of color from this pre- 

 cipitate on long contact. After the addition of a little alcohol, how- 

 ever, both solvents readily extracted the color. 



6. One hundred c.c. of serum from Jersey Cow No. 25 was 

 diluted with several volumes of water, a pinch of NaCl and a few 

 drops of glacial acetic acid added and the solution heated quickly to a 

 temperature just below the boiling point. The coagulum which formed 

 contained a very little pigment but the filtrate was golden-yellow. No 

 color could be extracted from the filtrate by carbon bisulphide, or by 



