1893.] on Turacin, a remarkable Animal Pigment. 45 



on several pigments extracted from feathers, has not submitted the in- 

 teresting substances he has described to quantitative chemical analysis. 



I must not, however, dwell further upon these preliminary mat- 

 ters. I have introduced them mainly in order to indicate how little 

 precise information has yet been gathered as to the constitution of the 

 greater number of animal pigments, and how difficult is their study. 



And now let me draw your attention to a pigment which I had 

 the good fortune to discover, and to the investigation of which I have 

 devoted I am afraid to say how many years. 



It was so long ago as the year 1866 that the solubility in water of 

 the red colouring matter in the wing-feathers of a plantain- eater was 

 pointed out to me. [One of these feathers, freed from grease, was 

 shown to yield its pigment to pure water.] I soon found that alkaline 

 liquids were more effective solvents than pure water, and that the 

 pigment could be precipitated from its solution by the addition of an 

 acid. [The pigment was extracted from a feather by very dilute 

 ammonia, and then precipitated by adding excess of hydrochloric 

 acid.] The next step was to filter off the separated colouring matter, 

 and to wash and dry it. The processes of washing and drying are 

 tedious and cannot be shown in a lecture. But the product obtained 

 was a solid of a dark crimson hue, non-crystalline, and having a 

 purple semi-metallic lustre. I named it turacin (in a paper published 

 in a now long-defunct periodical ' The Student and Intellectual 

 Observer,' of April, 1868). The name was taken from " Touraco,'" 

 the appellation by which the plantain-eaters are known — the most 

 extensive genus of this family of birds being Turacus. 



From the striking resemblance between the colour of arterial 

 blood and that of the red touraco feathers, I was led to compare 

 their spectra. Two similar absorption bands were present in both 

 cases, but their positions and intensities differed somewhat. Naturally 

 I sought for iron in my new pigment. I burnt a portion, dissolved 

 the ash in hydrochloric acid, and then added sodium acetate and 

 potassium ferrocyanide. To my astonishment I got a precipitate, 

 not of Prussian blue, but of Prussian brown. This indication of the 

 presence of copper in turacin was confirmed by many tests, the metal 

 itself being also obtained by electrolysis. It was obvious that the 

 proportion of copper present in the pigment was very considerable — 

 greatly in excess of that of the iron (less than ■ 5 per cent.) in the pig- 

 ment of blood. 



Thus far two striking peculiarities of the pigment had been 

 revealed, namely, its easy removal from the web of the feather, and 

 the presence in it of a notable quantity of copper. Both facts 

 remain unique in the history of animal pigments. The solubility 

 was readily admitted on all hands, not so the presence of copper. It 

 was suggested that it was derived from the Bunsen burner used 

 in the incineration, or from some preservative solution applied to the 

 bird-skins. And it was asked " How did the copper get into the 

 feathers?" The doubters might have satisfied themselves as to 



