330 CHOLETELIN. [BOOK II. 



Bilirubin is suspended in alcohol and the mixture 

 treated with nitrous acid, evolved by the action of 

 nitric acid on arsenic. The liquid assumes successively all the 

 colours of Gmelin's reaction, the bilirubin dissolves and a clear liquid 

 is obtained of a yellowish red colour and possessed of slight tinctorial 

 power. When this liquid is poured into water, choletelin separates 

 in the form of flakes having the colour of ferric oxide ; these, when 

 dried, furnish a brown powder. Choletelin has not been crystallised ; 

 it is soluble in alkaline solutions, from which it is precipitated on 

 the addition of acids ; it is soluble in chloroform, alcohol, ether 

 and acetic acid. 



Acid solutions containing choletelin, as for example the yellow 

 liquid which is obtained in the final stage of Gmelin's reaction, 

 exhibit an absorption band between 6 and F; this absorption band 

 is generally visible at the same time as the two bilicyanin bands, 

 though it does not, as Heynsius and Campbell believed, belong to 

 that substance. 



According to the observations of Maly and of Liebermann 1 , 

 neutral alcoholic solutions of choletelin exhibit no definite absorption 

 band, and the accuracy of their statements is placed beyond doubt 

 by the very complete spectro-photometric determinations of Vierordt 2 , 

 who made the interesting additional observation that an alkaline 

 solution of biliverdin left to itself for 56 days yielded results on 

 spectro-photometric analysis, which corresponded exactly with those 

 which would be yielded by a solution containing a mixture of pure 

 biliverdin and choletelin. 



Relations of We have already referred to the fact (p. 320) that 



choletelin to the action of nitric and nitrous acids on bilirubin, as 

 the bile colour- determined by a comparison of the elementary com- 

 position of bilirubin, biliverdin and choletelin, is one of 

 progressive oxidation and that the amount of nitrogen remains 

 unchanged. 



C N 



Bilirubin contains 67'IJ 9'8g 16'8J 



Biliverdin 63'6,, 9'3,, 21'2,, 



Choletelin 55'5,, 91 30'0,, 



Relying on the very misleading fact that the band observed in 

 acid solutions of choletelin occupies very nearly the position of the 

 well-marked band of hydrobilirubin, Stokvis, as well as Heynsius 

 and Campbell, expressed the belief that the products of the action 

 of nascent hydrogen, on the one hand, and of nitric and nitrous 



1 Leo Liebermann, ' Ueber Choletelin und Hydrobilirubin," Pfliiger's Archiv, 

 Vol. x. (1874), p. 246. 



2 K. Vierordt, ' Physiologische Spectralanalysen, ' Zeitschrift fiir Biologic, Vol. x. 

 (1874), pp. 2158 and Vol. x. 399409. A very complete abstract of the part of this 

 paper which deals with the spectro-photometry of the bile-colouring matters is given in 

 Maly's Jahresbericht, Vol. iv. p. 76 85. A table giving the spectro-photometric 

 constants of choletelin is to be found in Kriiss's ' Kolorimetrie, <fec.' p. 221. 



