244 BILIVERDIN. 



chloride is added ; this precipitates the pigment as a compound 

 with barium (?). The precipitate is then collected on a filter, 

 washed with water and alcohol, and decomposed with dilute 

 hydrochloric acid ; this liberates the biliverdin which is simultan- 

 eously precipitated as a fiocculent mass, and is then washed with 

 ether to remove all fat and dissolved in alcohol. The alcoholic 

 solution is finally filtered and by spontaneous evaporation yields 

 a dark-green glittering residue of impure biliverdin. To obtain 

 the pigment pure it must be prepared from bilirubiu. The con- 

 version may be effected in several ways. 1 (i) Bilirubin is dissolved 

 in a dilute alkali and exposed for some time to the air in thin 

 layers, 'whereby it is slowly oxidised into biliverdin. When the 

 conversion is complete, the pigment is precipitated by the addition 

 of hydrochloric acid, thoroughly washed with water, dissolved in 

 absolute alcohol, and precipitated by an excess of water or by 

 spontaneous evaporation of the alcoholic solution, (ii) By en- 

 closing bilirubin solutions in tubes with glacial acetic acid and 

 heating to 100. (iii) By the action of monochloracetic acid and 

 gentle heating at intervals for one or two days, (iv) Also by the 

 action of caustic potash on tribromobilirubiu. 2 



Apart from its colour biliverdin differs most characteristically 

 from bilirubin in its solubilities. It is (like bilirubin) soluble in 

 alkalis but insoluble in water and ether, whereas (unlike bilirubin) 

 it is insoluble in either chloroform, carbon bisulphide or benzol, 

 but readily soluble in alcohol and in glacial acetic acid. It has 

 further never been obtained in a crystalline form, and like bili- 

 rubin it shows no absorption bands but a somewhat strong absorp- 

 tion of the violet end of the spectrum. Treated with fuming 

 (yellow) nitric acid it gives Gmelin's reaction, starting now witli 

 a blue colour as a product of the first stage of its oxidation. It 

 also yields Huppert's reaction. (See above sub bilirubin.) 



Like bilirubin the quantitative determination of biliverdin is 

 dependent upon spectrophotometric methods. 3 



The formula assigned above to biliverdin represents its forma- 

 tion from bilirubin by simple oxidation. 4 This is undoubtedly 

 correct as against the older view of Staedeler that the change 

 consists not only in the assumption of oxygen but also of a mole- 

 cule of water. 



Bilifuscin, bilihumin, and biliprasin ars the names given by Staede- 

 ler to ill-defined and probably impure products obtained during his 

 investigations on bile-pigments as obtained from gall-stones. Bili- 

 prasiu is apparently only impure biliverdin (Maly). 



1 Maly, Sitzb. d. k. Akad. Wien, Bd. LXX. 3 Abth. 1874. Juli-Hft. 



2 Maly, Ibid. Bd. LXXII. 3 Abth. 1875. Oct.-Hft. 



3 See references sub bilirnbin. 



4 Maly, loc. cit. Thudichum, Jl. Chem. Soc. July, 1876. 



