524 CHEMISTRY OF THE PROTEIDS CHAP. 



While, according [ to Hoppe-Seyler, haemochromogen is the iron- 

 containing radical which, by its union with an albuminous substance, 

 forms haemoglobin and then becomes enabled to absorb oxygen, 1 

 Gamgee 2 stated, in 1898, that " probably haemochromogen does not 

 exist preformed in haemoglobin and its compounds." He has promised 

 to throw more light on this question. 



Hsematoporphyrin 



The methods of preparing haematoporphyrin from haematin have 

 already been referred to on p. 509. Mulder's 3 iron-free haematin, or 

 haematoporphyriri, to use Hoppe-Seyler's terminology, may be obtained by 

 either the action of concentrated H 2 S0 4 on haematin ; by treating haemin 

 with a saturated solution of hydrobromic acid in glacial acetic acid ; by 

 the reduction of acid alcoholic haematin solutions ; by acting on haemo- 

 chromogen or haemoglobin with dilute mineral acids (see p. 508). The 

 haematoporphyrin prepared from haematin with strong H 2 S0 4 is the 

 anhydride of the preparation obtained with hydrobromic acid, accord- 

 ing to Nencki and Sieber. 4 The H 2 S0 4 preparation is almost insoluble 

 in alcohol, ether, and dilute acids, but readily soluble in alkalies ; the 

 Br-preparation is readily soluble in fixed alkalies and their carbonates, 

 and also in dilute mineral acids and alcohol, but only slightly soluble 

 in ether, amyl-alcohol, benzene, and chloroform, somewhat more 

 soluble in acidified amyl-alcohol and acetic ether, and almost insoluble 

 in water and dilute acids. 



The reconversion of haematoporphyrin into haematin by the in- 

 corporation of iron has also been accomplished : Struck by the ease 

 with which iron is removable from reduced hsematin or haemo- 

 chromogen, Laidlaw attempted to replace the iron and was successful. 

 To 1 gramme of haematoporphyrin prepared by Nencki's method, dis- 

 solved in dilute ammonia and warmed on the water-bath in a flask, to 

 exclude air as much as possible, were added some Stoke's fluid 

 prepared from 2 grammes of ferrous sulphate (see p. 478) and a few 

 drops of a 50 per cent solution of hydrazin-hydrate. After one to 

 two hours, care having been taken to replace the evaporated ammonia 

 and to keep the mixture thoroughly reduced by hydrazin, a solution 

 is obtained which shows the absorption-bands of haemochromogen. 

 On shaking the solution with air it is converted into alkaline haematin. 



1 Hoppe-Seyler, Zeitschr. f. physiol. Chem. 13. 492-493 (1889). 



2 A. Gamgee, Schdfers Textbook of Physiol. 1. 258 (1898). 



3 Mulder, 'Uber eisenfreies Hsematin,' Journ. f.prakt. Chem. 32. 186 (1844). 



4 Nencki and Sieber, Sitzb. d. kais. Akad. de Wiss. Wien. 1889, year 1888, vol. 

 97, p. 80 ; and Arch. f. experim. Pathol u. Pharm. 24. 430 (1888). 



