BILE PIGMENTS AND THEIR DERIVATIVES. 387 



In the presence of bilirubin it is soluble in chloroform, although diffi- 

 cultly soluble in this solvent alone ; hence, after treatment with chloroform in 

 preparing bilirubin, both substances come into solution. When the chloroform 

 solution is concentrated, and excess of alcohol added, the bilirubin is pre- 

 cipitated, while the bilifuscin remains soluble, and is found in the alcoholic 

 filtrate along with some cholesterin and higher fatty acids. After removal of 

 the alcohol by evaporation, the residue is treated with ether, which dissolves 

 out these impurities, and chloroform, which removes any traces of bilirubin 

 left behind. The almost black, dark brown residue so obtained, was termed 

 bilifuscin by Sta'deler ; l who made incomplete analyses of it, from which he 

 deduced the formula C 1G H 20 N 2 4 (?). When quite pure, bilifuscin does not 

 give Gmelin's reaction ; 2 it is found in very old post-mortem bile 3 as well as 

 in gallstones, but not in fresh bile. Bilifuscin has only been obtained in an 

 amorphous form ; it is soluble in alcohol and in alkalies ; almost insoluble in 

 water, ether, and chloroform ; its relationship to bilirubin is unknown. The 

 biliprasin of Sta'deler 4 is probably only a mixture of bilifuscin and biliverdin. 

 Bilihumin is a name used by the same observer to designate a black mass 

 taken up by strong solution of ammonia, from the residue of gallstones 

 which have been thoroughly exhausted with chloroform, alcohol, and ether; 

 it does not give Gmelin's reaction. 



Hydrobilirubin (C 32 H 40 N 4 7 ), a reduction product of bilirubin, is an 

 important substance, from the connection it makes between the bile 

 pigments, those of the urine and the products of disintegration of 

 haemoglobin. 



Maly 5 first obtained it by the action of nascent hydrogen (from sodium 

 amalgam) on an alkaline solution of bilirubin ; biliverdin similarly treated 

 also yields it, being first converted into bilirubin. At the end of the reaction 

 the light brown coloured fluid is decanted from the mercury, and acidified 

 with hydrochloric acid. On the addition of the acid the solution becomes 

 much darker in colour, and abundant dark brown flocks of hydrobilirubin 

 separate out; these are separated from the solution, dissolved in ammonia, 

 reprecipitated with hydrochloric acid, and washed with water. After so 

 washing away all the salts the pigment becomes less soluble in water. After 

 drying it forms a dark reddish-brown powder, easily soluble in alcohol, or a 

 mixture of alcohol and ether ; not so soluble in ether alone. These solutions 

 have, when concentrated a reddish brown, when dilute a rose colour. 

 Chloroform dissolves it to form a yellowish-red solution. In alkalies it 

 dissolves to a pale yellow solution, becoming red on the addition of an acid. 

 Maly ascribes the yellow colour to a compound with the alkali, the red to 

 the free substance. 



Hydrobilirubin in solution has an absorption spectrum, showing a 

 dark band between I and F. On addition of ammonia this band fades 

 out, but reappears a little to the left on the addition of a trace of zinc 

 chloride to the solution. This solution containing zinc chloride and 

 ammonia has a rose colour and a green fluorescence. Hydrobilirubin 

 once formed does not readily give Gmelin's test ; that is to say, it is not 

 easily oxidisable again to bilirubin or biliverdin. 



Maly recognised his new substance as identical with a urinary 



1 Vrtljschr. d. naturf. Gesellsch. in Zurich, 1863, Bd. viii. 



2 Briicke, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1860, Bd. vi. S. 173. 



3 Simony, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1876, Bd. vi. S. 75. 



4 Loc. cit. 



5 Jahresb. u. d. Fortschr. d Thier-Chem., Wiesbaden, 1872, Bd. ii. S. 232. 



