326 HYDROBILIRUBIN. [BOOK II. 



The precipitated body to which Maly assigned the name of 

 hydrobilirubin is, like the bilirubin from which it is derived, soluble 

 in solutions of ammonia and the alkaline hydrates, from which it is 

 precipitated on the addition of acids. Unlike bilirubin, the reduction 

 product is very readily soluble in alcohol, and its alkaline brown 

 solutions, when concentrated, assume a garnet-red tint on the addition 

 of acids or, if dilute, appear of a rose-red colour. Solutions of hydro- 

 bilirubin are incapable of assuming a green tint under the circum- 

 stances which cause solutions of bilirubin to become green. Chloro- 

 form dissolves hydrobilirubin, acquiring an orange colour, and gives 

 up the pigment to alkaline solutions when treated with these. 



Hydrobilirubin has not hitherto been crystallised. It appears to 

 form readily soluble compounds with the alkalies and alkaline earths, 

 and sparingly soluble or insoluble compounds with the heavy metals 1 , 

 From the results of his analyses, Maly assigned to hydrobilirubin the 

 empirical formula C^H^N^, and explains its relation to bilirubin 

 by the following equation : 



CJB^NA + H 2 + H 2 = C 32 H 40 N 4 7 



Bilirubin. Hydrobilirubin. 



Abel determined the molecular weight of hydrobilirubin by 

 Eaoult's method and obtained results which agree with Maly's 

 formula 2 . 



When treated with one drop of sulphuric acid and a tiny grain of 

 saltpetre, hydrobilirubin exhibits the variegated tints characteristic 

 of Gmelin's reaction. This reaction of hydrobilirubin may be con- 

 veniently referred to as 'Liebermanris reaction,' after its discoverer 3 . 



Amongst the most striking characteristics of hydrobilirubin are 

 its properties of fluorescence, when treated with zinc chloride, and its 

 absorption spectrum under various conditions. 



Whereas solutions of bilirubin and biliverdin exhibit no absorption 

 bands, acid (red) solutions of hydrobilirubin exhibit a dark band 

 between b and F, which fades on the addition of ammonia, but 

 becomes again much darker, and shifts a little towards the red end, 

 when the ammoniacal solution is treated with a couple of drops of 

 zinc chloride. The zinc chloride solution, when examined by trans- 

 mitted light, is of a rose-red or a garnet-red colour according to 

 concentration, and exhibits a beautiful green fluorescence which 

 disappears on the addition of acids and reappears on the addition of 

 ammonia. 



1 For a more recent research on Hydrobilirubin than Maly's consult the 

 following: Ludwig Disque", ' Ueber Urobilin ' (aus dem physiol.-chem. Institut zu 

 Strassburg). Zeitschr. f. phys. Chemie, Vol. n. (1879), pp. 259272. 



2 John J. Abel 'Bestimmung des Moleculargewichtes der Cholalsaure, des Choles- 

 terins und des Hydrobilirubins nach dem Raoult'schen Methode' (Nencki's Laby. 

 Bern.). Monatsch. f. Chemie, Vol. xi. (1891), pp. 6170. 



3 Leo Liebermann, 'Ueber Choletelin und Hydrobilirubin,' Pfliiger's Archiv, Vol. x. 

 (1874), p. 246. 



