328 BILICYANIN. [BOOK n. 



bands, of organic fluids or extracts, and of the changes which they exhibit 

 under the influence of certain reagents. Such a study should only afford 

 hints for investigations to be conducted by the recognised methods of 

 chemical investigation. It is only by a spectro-photometric study of a 

 large number of spectral regions that the identity of, or the optical 

 differences existing between two bodies can be established. So great are 

 the modifications in light absorption introduced by comparatively trivial 

 circumstances that the greatest caution should be exercised in concluding 

 as to differences between otherwise related bodies on the ground of some 

 variation in their powers of absorbing light. 



Bilicyanin, 



It has already been stated that when bilirubin is subjected to the 

 oxidising action of nitric and nitrous acids, one stage in the reaction 

 which ensues (Gmelin's reaction) is characterized by a beautiful blue 

 colour and by a somewhat characteristic absorption spectrum. Several 

 observers have attempted to separate the body upon which the blue 

 colour depends and. although it has never yet been obtained in a 

 state to admit of scientific research, it has already received various 

 names. 



Stadeler 1 was the first to attempt to separate this 

 Preparation. co } ourm g ma tter. He added concentrated nitric acid, 

 containing some nitrous acid, drop by drop, to a dilute ammoniacal 

 solution of bilirubin, adding from time to time ammonia in quantity 

 sufficient nearly to neutralise the excess of acid ; there is thus 

 obtained a green flocculent precipitate which gradually turns blue. 

 After washing with water, the green pigment is extracted by means 

 of alcohol, which leaves a dark blue powder undissolved. The 

 quantity of this substance obtained by Stadeler did not permit of its 

 investigation. 



JafFe' 2 modified Stadeler's method somewhat. An alcoholic 

 solution of biliverdin, or a mixed ammoniaca] and alcoholic solution 

 of bilirubin, is treated exactly as Stadeler recommended. As soon 

 as the blue colour has been developed, the liquid is mixed with 

 chloroform and distilled water and shaken. The blue chloroform 

 solution is repeatedly shaken with distilled water, any biliverdin 

 which has separated is filtered off, and the chloroform solution allowed 

 to evaporate spontaneously. The residue is freed from traces of 

 biliverdin by repeated solution in chloroform. 



Stokvis 3 , and afterwards Heynsius and Campbell 4 , attempted to 



1 Stadeler, 'Ueber die Farbstoffe der Galle,' Annalen der Chemie u. Pharrn. 

 Vol. cxxxn. (1864), p. 333. 



2 Jafte, 'Zur Kenntniss der Gallen und Harnpigmente,' Centralblatt f. d. med. 

 Wissenschaft, 1868, p. 242. 



3 B. J. Stokvis, 'Ueber Gallenfarbstoffe,' Ber. d. d. Chem. Gesellsch. Berlin, 1872, 

 p. 583. Maly's Jahresbericht, Vol. n. 239; 'Das Gmelin'sche (blaue) Oxydations- 

 product der Gallenfarbstoffe.' Centralblatt f. d. med. Wissenschaft, . 1872, no. 50. 

 Maly's Jahresbericht, Vol. n. p. 239. 



4 Heynsius and Campbell, ' Die Oxydationsproducte der Gallenfarbstofife und ihre 

 Absorptionsstreifen,' Pfliiger's Archiv, Vol. iv. (1871), pp. 529 et seq. 



