76 PHYSIOLOGICAL CHEMISTRY. 



is obtained which is called by HOPPE-SEYLER hwmochromogen, by 

 other investigators (STOKES) reduced hoematin. In the presence 

 of oxygen, haemochromogen is quickly oxidized to haematin, and 

 we obtain in this case as a colored decomposition product 

 another coloring matter, Jicematin. As haemochromogen is easily 

 converted by oxygen into haematin, so this latter may be reconverted 

 into haemochromogen by reducing substances. 



Hsemochromogen was discovered by HOPPE-SEYLER to whom of 

 all investigators we are more indebted for our knowledge in regard 

 to the blood-coloring matters and their decomposition products. He 

 has also lately been able to obtain this coloring matter as crystals. 

 Haemochromogen is, according to HOPPE-SEYLER, the colored 

 atomic group of haemoglobin and its combination with gases, 

 and this atomic group is combined with albumin in the coloring 

 matter. The characteristic absorption of light depends on the 

 haemochromogen, and it is also this atomic group which binds in 

 the oxyhaemoglobin 1 mol. oxygen and in the carbon monoxide 

 haemoglobin 1 mol. carbon monoxide with 1 atom iron. HOPPE- 

 SEYLER has observed a combination between haemochromogen and 

 carbon monoxide, and this combination shows the spectral appear- 

 ance of carbon monoxide haemoglobin. 



An alkaline haemochromogen solution has a beautiful red color. 

 It shows two absorption-bands, first described by STOKES, of which 

 the one is darker and lies between D and E, and the other, broader 

 but not so dark, covers the lines E and b. In acid solution haemo- 

 chromogen shows four bands, which according to JADERHOLM de- 

 pend on a mixture of haemochromogen and haematoporphyrin (see 

 below), this last formed by a partial decomposition resulting from the 

 action of the acid. 



Haemochromogen may be obtained as crystals by the action of 

 caustic soda on haemoglobin at 100 C. in the absence of oxygen 

 (HOPPE-SEYLER). By the decomposition of haemoglobin by acids 

 (of course in the absence of air) we obtain haemochromogen con- 

 taminated with a little haematoporphyrin. An alkaline haemochro- 

 mogen solution is easily obtained by the action of a reducing sub- 

 stance (STOKES* reduction liquid) in an alkaline haematin solution. 



Haematin, also called Oxyhaematin, is sometimes found in old 

 transudations. It is formed by the action of gastric or pancreatic 



