320 THE SPECTRUM OF GMELIN'S REACTION. [BOOK II. 



The green tint is due to the production of biliverdin, which as will 

 be afterwards shewn is the first stage in the oxidation of bilirubin. 

 The blue tint is due to an imperfectly studied body termed bili- 

 cyanin ; the final reddish- orange colour is due to choletelin. 



Maly in commenting on the nature of the action exerted by nitric acid 

 on bilirubin makes the following remarks : 



" Nitric or nitrous acid can oxidize, form nitro-compounds, give rise to 

 isomers, effect decompositions, substitute hydroxyl- for amido-groups, 

 convert amido-acids into diazo-compounds, &c., so that from biliverdin 

 onwards no conception as to the nature of the colouring matters formed 

 in Gmelin's reaction could be formed were it not for choletelin, the 

 analysis of which settles the question, shewing that in Gmelin's reaction 

 no N is given off, but that a progressive oxidation occurs 1 . 



Carbon. Nitrogen. Oxygen. 



. Bilirubin contains in 100 pts. 67'1 9'8 16'8 



Biliverdin 63'6 9-3 21-2 



Choletelin 55-5 9-1 30-0 



It is no improbable conclusion that the yet unisolated blue and red 

 bodies are intermediate oxidation products." 



The spec- In 1886 Jaffe 2 made a series of interesting observa- 



trum of Gme- ^ ons on fc ne spectroscopic characters of the colouring 

 reaction. matters produced in Gmelin's reaction, shewing that 

 the different tints corresponded with characteristic alterations in the 

 spectrum. He found that with the commencement of the blue 

 colour (2nd stage of Gmelin's reaction) a broad absorption band 

 appears which extends between C and D, but nearer to the latter 

 than the former, and which extends half way between D and E. By 

 diluting the solution or examining a somewhat thinner layer the 

 broad absorption band above described, appears composed of two 

 bands within defined edges, separated by a clear interspace at D. 

 Jaffe designated these two bands, the a and ft bands. Almost at 

 the same time, but really somewhat later, than the bands just 

 described, a third band 7 became perceptible which is situated 

 between b and F but nearer F. This band increases in distinctness 

 as the bands a and ft gradually fade. 



In 1871 the late Prof. Heynsius of Leyden in association with 

 Dr J. F. F. Campbell 3 made a research in which they confirmed and 

 extended the observations of Jaffe'. They assigned the name of 

 cholecyanin to the blue body which occasions the bands a and ft 

 and shewed that the band 7 is caused by the presence of choletelin 

 which Maly had described. We may then speak of the spectrum of 



1 Article ' Galle,' Hermann's Handbuch, Vol. vn. p. 164. 



2 Jaffe, Centralblatt f. d. med. Wissenschaften (1868), p. 241. 



3 Prof. A. Heynsius und Dr J. F. F. Campbell, 'Die Oxydations-producte der 

 Gallenfarbstoffe und ihre Absorptionsstreifen ' (with a plate). Pfliiger's Archiv, Vol. iv. 

 (1871), p. 497546. 



