506 CHEMISTRY OF THE PROTEIDS CHAP. 



The spectrum is that of a reduction-product of CN-haematin, and is 

 not that of haemochromogen, as asserted by Szigeti. 



Cyan-methaemoglobin, according to Haldane, gives a spectrum 

 resembling that of reduced haemoglobin. It is not changed at first 

 visibly by the addition of ammonium sulphide, but on warming the 

 solution and allowing it to stand, the cyan-methsemoglobin is gradually 

 reduced to haemoglobin. 



Cyanhaematin and cyan-methsemoglobin agree in not being affected 

 in any way by a vacuum (Haldane). 



v. Zeynek 1 has obtained cyan-methsemoglobin in crystals, and 

 has also examined it spectro-photometrically. In neutral and alkaline 

 solutions it shows a broad band in the green which possesses 

 its greatest intensity of absorption at A535, while reduced haemo- 

 globin shows the maximum absorption at A547, according to Robert 

 and v. Zeynek. The absorption-coefficient measured at Hiifner's 

 place equals 1'29, according to Bock and v. Zeynek. 



Cyan-methsemoglobin contains one molecule of HCN ( = 0*158 per 

 cent) for one molecule of haemoglobin. It is converted into hsemo- 

 globin not only by reducing agents, but also by putrefaction. 



Azo-imide Methsemoglobin 



L. Smith and C. Gr. L. Wolf 2 have studied the action of azo-imide 



N \ 



or hydrogen nitride || /N H, which is the only substance known, the 



N X 



an-ion of which is composed of a single N-atom. It resembles hydro- 

 cyanic acid in its properties, and forms with methaemoglobin a com- 

 pound resembling that formed by HCN. 3 



Acetylen-hsemoglobin 



This compound has been described by Liebreich and Bistrow 4 in 

 1868, but probably does not exist, according to Gamgee. 5 



1 E. v. Zeynek, Zeitschr. /. physiol. Chem. 33. 426 (1901). 



2 Smith and Wolf, Journ. of Med. Research, 12. 451 (1904). 



3 Abstract by Alsberg in Zentralbl. f. Physiol. 19. 41 (1905). 



4 0. Liebreich and A. Bistrow, Ber. d. deutsch. chem. Ges. 1. I. 220 (1868). 



5 Gamgee, Schafer's Text-book of Physiology, 1. 242 (1898). 



