THE RED BLOOD-CORPUSCLES 933 



temperature has fallen to 60 C. the liquid is again warmed, and then allowed 

 to cool. Crystals are formed which are allowed to stand for twelve hours and 

 are then separated and washed by decantation, first with distilled water and 

 then with graduated strengths of alcohol. In order to purify these crystals 

 the crude material is shaken for fifteen minutes with a mixture of chloroform 

 and pyridine. The solution is filtered and then thrown into glacial acetic acid 

 previously saturated with sodium chloride and heated to 105 C. A few drops 

 of concentrated hydrochloric acid are then added and the mixture allowed to 

 stand for twenty-four hours. The crystals which separate out are filtered off, 

 washed with dilute acetic acid, and then dried. 



Haemin crystals have been regarded as hydrochloride of haematin. 

 Elementary analysis shows that they have the following formula 

 (Kiister): C 34 H 33 4 N 4 Cl.Fe. By dis- 

 solving haemin in alkalies and throwing * "^-^x* 

 the solution into an excess of acid a I/ \ "^ * " 



Tp 



precipitate is obtained which is hsematin. J V H 



SK ^ H 



Hsematin forms a brown powder of bluish- /Js -^ ^ \ 



3$ ^Bt^ v * *. T 



black colour and metallic lustre. It js \ * v *V \-\NX 



insoluble in water, alcohol, or ether, but "^ V ^ 

 is slightly soluble in glacial acetic acid / \; 



and in absolute alcohol. It is easily \- 

 soluble in concentrated sulphuric acid, 



but undergoes decomposition, losing its ^ 



atom of iron and being transformed into ~L 



hfsmatoporphyrin, which forms a deep FIG. 358. Hsemin crystals, 

 purple solution. The formula of haematin 



has not yet been ascertained with certainty. It is either C 34 H 34 N 4 O.Fe 

 or 34 H 32 N 4 5 Fe. Its compounds with acids and alkalies are 

 spoken of as acid and alkaline haematin, and each gives a charac- 

 teristic absorption spectrum (Fig. 359). The alkaline solutions exhibit 

 one indistinct absorption band between C and D, the acid solutions 

 an absorption band also between C and D but nearer to C, and 

 resembling somewhat the band presented by methaemogiobin. Accord- 

 ing to Hoppe-Seyler and Gamgee perfectly pure solutions of haematin 

 in alkalies are quite unaffected by reducing agents ; in the presence of 

 certain foreign matters, however, alkaline haematin, when treated 

 with reducing agents, exhibits a spectrum known as that of reduced 

 alkaline haematin, which is practically identical with that of 

 haemochromogen. The same change is further observed when alkaline 

 haematin made by the action of alkalies on ordinary blood is treated 

 with reducing agents such as ammonium sulphide. Since this sub- 

 stance haemochromogen is responsible for the respiratory functions of 

 the haemoglobin, i.e. the power of its molecule to form unstable com- 

 pounds with oxygen, its preparation merits fuller consideration. 

 Hcemochromogen is prepared by the action of caustic alkalies on 



