BILE PIGMENTS AND THEIR DERIVATIVES. 387 
In 1 lie 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 Stadeler ; l who made incomplete analyses of it, from which he 
deduced the formula C,,.l I ,.,X. J (J 4 (?). When quite pure, bilifuscin does not 
give Gmelin's reaction :- 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 Stadeler i 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\,,H 4(l X 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 ' 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 b 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. naiurf. Gesellsch. in Zurich, 1863, Bd. viii. 
2 Briicke, Untersuch. z. Naturl. d. Mensch. v.. d. Thiere, I860, Bd. vi. S. 173. 
3 Simony, Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1S7G, Bd. vi. S. 75. 
4 Loc. cit. 
5 Jahresb. ii. d. Fortschr. d Thier-Chem., Wiesbaden, 1872, Bd. ii. S. 232. 
