HANDBOOK FOB BIO-CHEMICAL LABORATORY. 29 



Properties. Bilirubin occurs partly amorphous and partly 

 crystalline, as rhombic plates whose obtuse angles are often 

 rounded. It is insoluble in water, almost insoluble in ether, 

 and very sparingly soluble in alcohol; easily soluble in chloro- 

 form, especially in the warmth, and less soluble in benzol, carbon 

 disulphide, amyl alcohol, fatty oils, and glycerin. Its solutions 

 show no absorption-bands and have, even on diluting greatly 

 (1 to 50,000), a decided yellow color. The combinations with 

 alkalies are insoluble in chloroform. Bilirubin forms com- 

 pounds with bases such as sodium, calcium, barium, lead, and 

 silver in ammoniacal solution. On allowing an alkaline solu- 

 tion of bilirubin to stand in contact with the air it gradually 

 absorbs oxygen, and green biliverdin is formed. 



Biliyerdin, C 16 H 18 N,0 4 or C 33 H S6 ]S\0 8 . 



Preparation. 1. Biliverdin is readily prepared by expos- 

 ing a thin layer of an alkaline solution of bilirubin to the air or 

 by passing a current of oxygen through the alkaline solution 

 until it has acquired a bright green color. Add hydrochloric 

 acid, which precipitates the biliverdin, filter, and wash the pre- 

 cipitate with water until no reaction for HC1 is obtained in the 

 filtrate. Dry the precipitate, dissolve in alcohol, and separate 

 the pigment by the addition of water to the alcoholic solution. 

 Any bilirubin present may be removed by extracting with 

 chloroform. 



2. Add Pb0 2 to an alkaline solution of bilirubin and stir. 

 The liquid assumes a dark green color in a few minutes; now 

 acidify with acetic acid, which precipitates a compound of bili- 

 verdin with lead. This combination is decomposed by means 

 of alcohol containing sulphuric acid in solution. The alcoholic 

 solution containing the biliverdin is separated from the lead 

 sulphate by filtration and the filtrate poured into water, which 

 precipitates the biliverdin. Collect the precipitate on a filter 



