25 o HAEMOGLOBIN. 
methsemoglobin " ; they are almost certainly caused by a mixture of de- 
composition products of oxyhemoglobin, brought about by the action of H 2 S 
upon it. 
Kk.matix (C 34 H 35 N 4 Fe0 5 , Hoppe-Seyler) ; (C 32 H 30 N 4 FeO 3 , Nencki 
and Sieber). 
As has been already stated, luematin is the colouring matter 
which results from the decomposition of oxyhemoglobin 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 examined with the spectroscope, which 
were originally described by Stokes as those of " reduced hcematin," now 
known as " heemochromogen" (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 " haemin " (see p. 252), the latter 
body should invariably be employed in the preparation of pure haematin. 
Pure crystallised liaeinin (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 lioceulent- 
brown precipitate is washed with hot distilled water imtil the washings 
give no turbidity with silver nitrate. The haematin thus precipitated is 
first dried at the temperature of 100°, and then at 115°, or even higher. 
Physiccd and chemical properties. — Haematin has not hitherto been 
crystallised. In the condition of utmost purity it possesses a bluish-black 
colour, and a very pronounced metallic lustre. AYhen 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. 
Hamiatin forms a crystalline compound with hydrochloric acid 
(haematin hydrochloride, or haemin), 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 haematin 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. 
Haematin 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 haematin incinerated. 
When boiled with concentrated potassium hydrate, luematin 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 lxxxi. p. 477 : V. D. Harris, 
Journ. Physiol., Cambridge and London, 1885, vol. v. p. 209 ; D. Axenneld, Centralbl. 
f. d. med. Jf'issensch., Berlin, 1S85, No. 47. 
