232 ILEMATIN. 



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 com- 

 pounds as oxy-haemoglobin and carbon -monoxide haemoglobin. 

 Further investigation, more particularly of the crystalline haemo- 

 chromogen, is needed for the final establishment of these views. 



9. Hsematin. C 34 H 36 N 4 Ee0 5 . 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 extrav- 

 asations 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 Klihne 2 

 may be advantageously employed, and yields not only solutions which 

 show strikingly the spectroscopic appearances of haematin in acid and 

 alkaline solution, but also finally a fairly pure and typical specimen 

 of haematin 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 ex- 

 tracts are mixed and filtered and form a strong solution (a) of haematin 

 in alkaline alcohol. A portion of this extract may be kept for spectro- 

 scopic examination. The remainder is strongly acidulated by the care- 

 ful 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 con- 

 sists of fairly pure haematin. This should finally be washed with 

 alcohol and ether and then dried for a prolonged period at 130-150 . 



To obtain pure haematin it is probably better to prepare it from 

 haemin whose purity as a mother substance can be ensured at the out- 



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



2 Physiol. Chem. 1868, S. 202. 



