CHEMICAL BASIS OF THE ANIMAL BODY. 233 



compound of haemochromogen with carbon-monoxide exhibiting the 

 absorption bands of carbon-monoxide haemoglobin and containing the 

 same amount of carbon-monoxide united to each atom of iron as does 

 that body, whereas haematin in alkaline solution will not unite with 

 carbon-monoxide. He therefore considers that haemoglobin is a 

 compound of a proteid with this haemochromogen, to which it owes 

 its colour, and that it is with the haemochromogen group rather 

 than with haemoglobin as a whole that the gases are united in the 

 formation of such compounds as oxy-haemoglobin and carbon-monoxide 

 haemoglobin. Further investigation, more particularly of the crystal- 

 line haemochromogen, is needed for the final establishment of these 

 views. 



9. Hsematin. Cg^^FeOs. 1 



When oxy-haemoglobin is decomposed by either acids or alkalis it 

 yields a proteid and a coloured substance known as haematin. This 

 decomposition may take place in old blood-clots or extravasations and 

 is readily produced by the action of either gastric or pancreatic juice 

 on oxy-haemoglobin, so that haematin is frequently found in the contents 

 of the alimentary canal and in the faeces, more especially with a flesh 

 diet. It has also been found in urine as the result of poisoning with 

 sulphuric acid or arseniuretted hydrogen. 



Preparation. The following method slightly modified after Kiihne 2 may be 

 advantageously employed, and yields not only solutions which show strikingly the 

 spectroscopic appearances of hasmatin in acid and alkaline solution, but also finally 

 a fairly pure and typical specimen of hsematin itself. Defibrinated blood is made 

 into a thin paste by mixture with potassium carbonate, and is then evaporated to 

 dryness on a water-bath. The dry residue is powdered, placed in a flask and 

 extracted with about four times its bulk of strong alcohol by boiling on a water- 

 bath. The deeply-coloured extract thus obtained is poured off and the residue 

 again extracted as before with alcohol, the process being repeated as long as any 

 colouring matter is extracted. The extracts are mixed and filtered and form a 

 strong solution (a) of haematin in alkaline alcohol. A portion of this extract may 

 be kept for spectroscopic examination. The remainder is strongly acidulated by 

 the careful addition of sulphuric acid, any precipitate which is formed is removed 

 by filtration, and the filtrate (b) provides a typical solution of haematin in acid 

 alcohol. A portion of this may as before be kept for spectroscopic examination. 

 The remainder is made alkaline by the addition of an excess of ammonia and filtered ; 

 the filtrate (c) is, as in the case of (a), a solution of haematin in alkaline alcohol, but 

 now the extraneous salts present are chiefly those of ammonium. The filtrate (c) is 

 finally evaporated to dryness on a water-bath, extracted with several portions of boiling 

 water and the undissolved residue consists of fairly pure hasmatin. This should 

 finally be washed with alcohol and ether and then dried for a prolonged period at 

 130150. 



1 Hoppe-Seyler, Med.-chem. Untersmh. 1871, Hft. 4, S. 523. 



2 Physiol. Chem. 1868, S. 202. 



