x NATURALLY OCCURRING COLOURING MATTERS 529 



formed when haemopyrrol is oxidised by the air. 1 If rabbits be fed 

 on haemopyrrol they excrete urobilin. It contains, as does hsematin, 

 four molecules of haemopyrrol (Nencki and Zaleski), 1 and possesses, 

 according to Maly, 2 the formula : 



BILIRUBIN. This colouring matter of the bile is also a derivative 

 of haematoporphyrin, for Virchow, 3 Jaffe, 4 and Salkowski 5 have shown 

 that bilirubin greatly resembles haematoidin or mesoporphyrin, if it is 

 not identical with it, and Maly 2 has further prepared urobilin or 

 hydrobilirubin by a simple reduction of bilirubin. Ku'ster, 6 finally, 

 has succeeded in getting the same hsematinic acids from bilirubin as he 

 obtained from hsematin. (For a fuller account of these pigments see 

 Roscoe and Schorlemmer's Handbook of Organic Chemistry, 9. 309 (1901).) 



H/EMOCYANIN. Instead of the iron - containing haemoglobin, 

 cephalopods possess in their blood a proteid containing copper. 

 This copper-albuminate the discoverer, Fredericq, 7 has called haemo- 

 cyanin. Subsequently it has been very thoroughly investigated by 

 Henze, 8 who was the first to prepare it in a pure state. Haemocyanin 

 may be obtained in well -formed crystals by using the Hofmeister- 

 Hopkins method of salting out (see p. 325). Henze obtained the 

 following percentage composition : 



It gave all the colour- and precipitation tests of albumins and the 

 biuret reaction, without copper having to be added. It is soluble in 

 water, in salt solutions, and in alkalies. Magnesium sulphate does 

 not salt out, and the limits for ammonium sulphate lie between 3 '5, 

 and 10. Its coagulation -temperature lies between 68 and 72. 

 Towards acids it is as sensitive as is haemoglobin, becoming decom- 

 posed into albumin and copper, but haemocyanin is not a copper salt, 

 as it does not give the reactions of copper-ions without having been 

 decomposed. 



Haemocyanin binds oxygen, and gives off the latter, when a stream 

 of hydrogen, carbonic oxide, and especially carbon dioxide 7 is passed 



1 M. Nencki and J. Zaleski, Ber. d. deutsch. chem. Ges. 34. I. 997 (1901). 



2 R. Maly, Zentralbl. f. d. med. Wiss. 1871, No. 54 ; Liebig's Annalen, 161. 368 

 (1872) ; 163. 77 (1872) ; Pfluger's Archiv, 2O. 331 (1879). 



3 R. Virchow, Virchow's Archiv, 1. 379 and 411 (1847). 



4 M. Jaffe, Virchow's Archiv, 47. 405 (1869) ; Zentralbl. f. d. med. Wiss. 1869, p. 

 177. 5 E. Salkowski, Hoppe-Seyler's Med.-chem. Unters. p. 436 (1871). 



6 W. Kiister, Ber. d. deutsch. chem. Ges. 35. II. 1268 (1902). 



7 L. Fredericq, Arch, de Zool. exper. 7- 535 (1878). 



8 M. Henze, Zeitschr. f. physiol. Chem. 33. 370 (1901). Here the older literature. 



2 M 



