THE BLOOD. 77 



juices on oxyhaemoglobin, and is therefore also found in the faeces 

 after hemorrhage in the intestinal canal, and also after a meat diet 

 and food rich in blood. It is stated that haematin may occur 

 in urine after poisoning with arseniuretted hydrogen. As shown 

 above, the haematin is formed by the decomposition of oxyhaemo- 

 globin, or at least of haemoglobin, in the presence of oxygen. 



The constitution of haematin may, according to HOPPE-SEYLEK, 



be expressed by the formula C^H^N^FeOg. According to NENCKI 



and SIEBER it has the formula C 32 H b2 N 4 re0 4 , and they claim that 



- haematin consists of a body not yet isolated, haemin, C^HgoN^FeOs > 



with 1 mol. H 2 0. 



Haematin is amorphous, dark brown or bluish black. It may 

 be heated to 180 C. without decomposition; on burning it leaves a 

 residue consisting of iron oxide. It is insoluble in water, dilute 

 acids, alcohol, ether, and chloroform, but it dissolves slightly in 

 warm glacial acetic acid. Haematin dissolves in acidified alcohol 

 or ether. It easily dissolves in alkalies, even when very dilute. The 

 alkaline solutions are dichroitic; in thick layers they appear red by 

 reflected light, and in thin layers greenish. The alkaline solutions 

 are precipitated by lime- and baryta-water, as also by solutions of 

 neutral salts of the alkaline earths. The acid solutions are always 

 brown. 



An acid haematin solution absorbs the red part of the spectrum 

 less and the violet part more. The solution shows a rather sharply- 

 defined band between C and D whose position may change with the 

 variety of acid used as a solvent. Between D and F a second, much 

 broader, less sharply-defined band occurs which by proper dilution 

 of the liquid is converted into two bands. The one between b and F y 

 lying near F, is darker and broader, the other, between D and E, 

 lying near E, is lighter and narrower. Also by proper dilution a 

 fourth very faint band is observed between D and E lying near D. 

 Haematin may thus in acid solution show four absorption-bands; 

 ordinarily one sees distinctly only the bands between C and D 

 and the broad, dark band or the two bands between D and F. 

 In alkaline solution the haematin shows a broad absorption-band, 

 which lies in greatest part between C and D, but reaches a little 

 over the line D towards the right in the space between D and E. 



Haematin is dissolved by concentrated sulphuric acid in the 



