232 H^EMOCHROMOGEN. 



either of these solvents showing two absorption bands between D and E very 

 similar to, though not identical with, the bands of oxy-hsemoglobin and a third 

 faint broad band at F. It is not however a respiratory pigment. 



8. Hsemochromogen. C 34 H 36 N 4 Fe0 5 (?). 



When (reduced) haemoglobin is treated with acids, or, better still, 

 with alkalis in the entire absence of oxygen it is decomposed into a 

 proteid and a coloured substance to which the name haemochromogen 

 was first given by Hoppe-Seyler 1 . When alkalis are used in its 

 preparation the solution obtained is of a brilliant purplish-red colour 

 and is characterised by two marked absorption bands, the stronger 

 lying halfway between D and E, the other and fainter between E and 

 b. These are identical with the bands of Stokes' reduced haematin in 

 alkaline solution (see Fig. 37, No. 3). When exposed to the air (oxygen) 

 the solution rapidly loses its brilliant colour, becomes dichroic, viz. : 

 red in thick and greenish in thin layers (cf. sub haematin) and now 

 yields an absorption spectrum, which exhibits one not very strongly 

 marked band in the yellow, to the red side of D and touching the 

 latter line. This is the spectrum of haematin in an alkaline solution 

 (see Fig. 37, Nos. 1 and 2). When the decomposition of the haemoglobin 

 is brought about by acids instead of alkalis, the coloured product is 

 similarly haemochromogen, but in this case unless special precautions 

 are taken some of the haemochromogen is itself further decomposed and 

 yields haematoporphyrin or iron-free haematin (see below). The mixture 

 thus obtained probably accounts for the four-banded spectrum as first 

 described by Hoppe-Seyler 2 . When a solution of haematin in alkali is 

 reduced with Stokes' fluid (see sub oxy-haemoglobin) or ammonium 

 sulphide the solution obtained shows two absorption bands identical 

 with those already described as characteristic of haemochromogen. 

 From these facts it would at first sight appear that reduced haematin 

 in alkaline solution and haemochromogen in a similar solution are 

 identical substances, and this is indeed the view which has been most 

 generally adopted. From a spectroscopic point of view they do appear 

 to be the same, but Hoppe-Seyler maintains that they are not 3 . 

 According to him haemochromogen is a simple product of the decompo- 

 sition of haemoglobin, while haematin is an oxidised product which 

 differs from true oxy-haemochromogen by being united to a smaller 

 amount of oxygen than is the former. He has further succeeded in 

 obtaining not only haemochromogen in a crystalline form 4 , but also a 



1 Med.-chem. Unters. Hft. iv. (1871), S. 540. Quoted in detail by Gamgee, 

 Physiol. Chem. Vol. i. p. 118. See also later Hoppe-Seyler, Zt. f. physiol. Chem. 

 Bd. i. (1877), S. 138. 



2 Loc. cit. Cf. Jaderholm (Swedish), Abstr. in Maly's Jahresb. 1874, S. 104, 

 1876, S. 86. But see Hoppe-Seyler, Physiol. Chem. 1881, S. 394. 



3 Zt. f. physiol. Chem. Bd. xra. (1889)', S. 477. 



4 By the action of strong caustic soda at 100 in the entire absence of oxygen. 



