250 HAEMOGLOBIN. 



methsemoglobin " ; they are almost certainly caused by a mixture of de- 

 composition products of oxy haemoglobin, brought about by the action of H 2 S 

 upon it. 



H^MATIN (C 34 H 35 N 4 Fe0 5 , Hoppe-Seyler) ; (C 32 H 30 N 4 Fe0 3 , Nencki 



and Sieber). 



As has been already stated, hsematin is the colouring matter 

 which results from the decomposition of oxyhsemoglobin by acids and 

 alkalies. In acid and alkaline solutions the body is characterised by 

 certain spectroscopic appearances, and especially by yielding, under 

 suitable conditions, when treated with reducing agents, a body possessing 

 the optical characters, when examine?!, with the spectroscope, which 

 were originally described by Stokes as those of " reduced hcematin" now 

 known as " JicemocJiromogen " (Hoppe-Seyler). 



Mode of preparation. As we are now in possession of an easy and in 

 all respects admirable method of preparing, in a state of great purity, the 

 crystalline hydrochlorate of haematin or " httanin " (see p. 252), the latter 

 body should invariably be employed in the preparation of pure haematin. 



Pure crystallised hsemin (prepared by Schalfijew's process) is dissolved 

 in a highly dilute solution of potassium hydrate, and the alkaline solution 

 is precipitated by means of dilute hydrochloric acid. The rlocculent- 

 brown precipitate is washed with hot distilled water until the washings 

 give no turbidity with silver nitrate. The hsematin thus precipitated is 

 first dried at the temperature of 100, and then at 115, or even higher. 



Physical and chemical properties. Hsematin has not hitherto been 

 crystallised. In the condition of utmost purity it possesses a bluish-black 

 colour, and a very pronounced metallic lustre. When finely powdered it 

 appears as a dark brown powder, which is distinctly pleochromatic. 



It is insoluble in water, alcohol, ether, and chloroform, but slightly 

 soluble in glacial acetic acid ; also in acidulated alcohol, but absolutely 

 insoluble in aqueous solutions of acids. It is very readily soluble in all, 

 even highly dilute, alkaline solutions. 



Hsematin forms a crystalline compound with hydrochloric acid 

 (hsematin hydrochloride, or hsemin), which, because of its importance, 

 will be separately described, and also others with hydrochloric and 

 hydrobromic acids. 1 



It combines with potassium and sodium, as well as with calcium, 

 barium, and other metals. The calcium and barium compounds are 

 obtained by precipitating ammoniacal solutions of hsematin by means 

 of solutions of calcium or barium chloride, but they have not been yet 

 obtained in a state of purity, and have not been analysed. 



Hsematin may be strongly heated to 180 C. without undergoing 

 decomposition. When heated further it is carbonised without previously 

 melting or taking fire, and liberates hydrocyanic acid, leaving a 

 residue of pure oxide of iron, which amounts to 12'6 per cent, of 

 the hsematin incinerated. 



When boiled with concentrated potassium hydrate, hsematin under- 

 goes no perceptible change ; when fused with caustic potash, it is very 

 slowly decomposed, and evolves ammonia. It is only attacked by 



1 M. C. Husson, Compt. rend. Acad. d. sc., Paris, tome Ixxxi. p. 477 ; A r . D. Harris, 

 Journ. Physiol., Cambridge and London, 1885, vol. v. p. 209; D. Axenfield, Centralbl. 

 f. d. med. Wissensch., Berlin, 1885, No. 47. 



