BILIRUBIN. 431 



in chloroform depends, according to KUSTER, on the fact that in its 

 preparation, derivatives which are readily soluble and contain chlorine 

 or other transformation products are formed, or perhaps the bilirubin 

 goes over into polymeric modifications having different solubilities. In 

 cold dimethylaniline it dissolves in the proportion of 1 : 100, and in hot 

 dimethylaniline much more readily. Its solutions show no absorption- 

 bands, but only a continuous absorption from the red to the violet end 

 of the spectrum, and they have a decided yellow color, even on diluting 

 greatly (1:500000), in a layer 1.5 cm. thick. The combinations of 

 bilirubin with alkali are insoluble in chloroform, and the bilirubin in solu- 

 tion in chloroform can be removed from this solution by shaking with 

 dilute alkali (differing from lutein). Solutions of bilirubin-alkali in 

 water are precipitated by the soluble salts of the alkaline earths and also 

 by metallic salts. If a dilute solution of alkali bilirubin in water is 

 treated with an excess of ammonia and then with a zinc-chloride solution, 

 the liquid is first colored deep orange and then gradually olive-brown 

 and then green. This solution first gives a darkening of the violet and 

 blue part of the spectrum, and then the bands of alkaline cholecyanin 

 (see below), or at least the bands of this pigment in the red between 

 C and D, close to C. This is a good reaction for bilirubin. The fol- 

 lowing reaction has been suggested by AucHls l . Treat 5 cc. of an alcoholic 

 solution of bilirubin (1:20000) which contains 1 drop of ammonia in 

 100 cc., with 5 to 6 drops of an alcoholic zinc acetate solution (1:1000) 

 and then 1 drop alcoholic iodine solution (1:100) when a beautiful bluish- 

 green coloration with a beautiful garnet-red fluorescence is obtained on 

 shaking. The spectrum shows a dark band between B and C, and a 

 pale band at D. If a few drops of hydrochloric acid are added to the 

 solution the color becomes violet, the fluorescence disappears and the 

 two JAFFE'S cholecyanin bands appear. This reaction is extremely 

 delicate. 



As EHRLICH first showed, bilirubin forms combinations with diazo 

 compounds, which have been closely studied by PROSCHER, ORNDORFF 

 and TEEPLE. 2 A test suggested by EHRLICH for bilirubin is based upon 

 this behavior with sulphodiazobenzene. 



If an alkaline solution of bilirubin be allowed to stand in contact 

 with the air, it gradually absorbs oxygen, and green biliverdin is formed* 

 This process is accelerated by warming. According to KUSTER, in this 

 case the alkali also has a splitting action upon the pigment, and among 

 the products formed we find haematinic acid. Biliverdin is formed only 



1 Compt. rend. soc. biol., 64. 



2 Ehrlich, Zeitschr. f. anal. Chem., 23; Proscher, Zeitschr. f. phyeiol. Chem., 39; 

 Orndorff and Teeple, 1. c. 



