494 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Cyanhaemoglobin. 



A solution of methaemoglobin piepared from horse's blood is treated with 

 5 per cent, hydrogen cyanide solution till the colour changes to red. One 

 quarter of its volume of alcohol is added. On cooling to o, crystals of cyan- 

 haemoglobin separate out. 



Cyanhsemoglobin forms long prisms which are hygroscopic and contain 

 5*7 per cent, of water. They dissolve in water giving a red solution which 

 has a shade of yellow. They contain '158 per cent, of cyanogen. * Its spectrum 

 in neutral or faintly alkaline solution shows a broad absorption band in the 

 green towards the violet end. It is converted by hydrogen sulphide into 

 haemoglobin. 



Haematin. 



Haemaiin is most easily prepared from hsemin, its hydrochloride. Hoppe- 

 Seyler obtained it from blood by the action of strong acetic acid in the pre- 

 sence of ether. The filtered ethereal solution deposits haematin in an amorphous 

 form. 



It is prepared from haemin by dissolving it in cold 10 per cent, sodium 

 hydroxide solution and carefully adding dilute hydrochloric acid to the solu- 

 tion. The precipitate is filtered off and washed. 



Haematin forms an amorphous blue-black solid which is insoluble in water, 

 alcohol, chloroform, or aqueous solutions of acids. It dissolves in acetic 

 acid, alcoholic solutions of acids and alkalies and pyridine. The acid solutions 

 are brown-red in colour, the alkaline solutions are dull green and dichroic. 

 Calcium and barium salts are obtained by adding the chlorides of these metals 

 to an ammoniacal solution. 



Solutions of haematin show the typical absorption spectra. 



Haemin. 



Several methods have been described for the preparation of haemin ; of 

 these, that of Schalfejeff gives the best yield and is the most convenient. 1 



200 c.c. of defibrinatcd blood are slowly added with stirring to i litre of 

 glacial acetic acid saturated with sodium chloride and heated to 90-95. 

 Tne temperature falls and is again raised to 90. The hot filtered solution 

 deposits crystals on cooling. They are filtered off, washed with water and 

 65 per cent, alcohol and dried in vacuo. They are recrystallised by dissolving 

 in 50 c.c. of a mixture consisting of 15 parts of 95 per cent alcohol, 4 parts of 

 water and i part of ammonia of sp. gr. "91, a process which takes about 30 

 minutes at room temperature. 



This solution is added to 4-6 times its volume of glacial acetic acid 

 saturated with sodium chloride at a temperature of 1 10. The crystals which 

 separate out on cooling are washed with 2 per cent, hydrochloric acid and 

 dried in vacuo. 3-4 gm. are obtained from a litre of blood. 



Willstatter has improved the Srlulfcjrff method : 



(i) Defibrinated blood or "filtered blood is allowed to drop in a stream 

 from a dropping funnel into 3 litres of glacial acetic acid containing some 

 solid sodium chloride, or i c.c. of saturated sodium chloride solution per litre, 

 contained in a 4 litre round-bottom flask and heated so that its temperature is 

 95. The end of the funnel is so high that the vapours do not come into 

 contact with the blood so as to cause coagulation and the acetic acid is stirred 

 continuously, avoiding contact of the blood with the sides of the vessel. The 

 li|ui 1 is heated for 15 minutes. H;L- nin crystallises and after 2-3 days is 

 fil errd off on cloth, washed with acetic arid, v.ater, alcohol and ether. 4-5- 

 5*5 gm. of pure luemin are obtained from i litre of blood. 



1 Other methods are given in the Zeit. Physiol. Chem., 30, 126 and 384 ; 29, 187 ; 49, 



47* 



