x H^MATIN-DERIVATIVES 509 



haemin has the tendency of crystallising with portions of such solvents 

 as amylalkohol, acetic acid, etc., as believed by Nencki and Sieber, 

 and Schalfejew, 1 but is due to impurities, according to Kiister (see 

 p. 517). Schalfejew had also observed the presence of an impurity 

 which could only be removed by repeated recrystallisation. 



Hcematoporphyrin. By the action of acids under certain conditions 

 described below, haematin is decomposed into a ferrous salt and the 

 iron -free compound called hsematoporphyrin. On dissolving, for 

 example, haematin or haemin in strong sulphuric acid, and then filtering 

 the mixture through asbestos, a clear purple-red solution is obtained. 

 Another method of preparing haematoporphyrin, namely, that of Hoppe- 

 Seyler, 2 is to enclose haematin or haemin dissolved in strong HC1 in 

 a sealed tube and to heat the latter up to 130. Nencki and Sieber 3 

 act on haernin, first at room-temperature and then on the water bath, 

 with glacial acetic acid saturated with hydrobromic acid. According 

 to Schulz 4 and Hoppe-Seyler-Thierfelder, 5 haemochromogen, i.e. reduced 

 hsematin, passes readily into hsematoporphyrin on being treated with 

 dilute acids. By these means are obtained purple or deep red solutions, 

 which deposit hsematoporphyrin on being diluted with water and on 

 being neutralised with caustic soda till the reaction is only faintly acid. 

 (See also p. 468.) 



The simplest and best method for preparing hsematoporphyrin is, 

 however, that of Laidlaw. 6 It is based on the observation that 

 " whereas oxyhaemoglobin yields hsematin to all strengths of mineral 

 acids (except concentrated sulphuric acid), reduced haemoglobin treated 

 in the same manner gives hsematoporphyrin." "The presence of 

 oxygen confers stability to the iron of blood pigments, and the simplest 

 explanation seems to be that the oxygen of oxyhsemoglobin is in 

 direct relation to the iron," for while 2 per cent hydrochloric acid can 

 split off the iron from the pigment in the reduced condition, it requires 

 the strongest hydrochloric acid, aided by heat and pressure, to effect the 

 cleavage in the oxidised pigment. By acting on reduced haemoglobin 

 with acids there is formed in the first instance hsemochromogen, and 

 the latter is then converted into the iron-free haematoporphyrin. 

 For reducing oxyhsemoglobin Laidlaw uses hydrazin-hydrate, as its 



1 M. Schalfejew, Chem. ZentralU. 18. 232. (1885) ; Maly's Jahresb. 15. 138 (1885). 



2 F. Hoppe-Seyler, ZentralU. f. d. med. Wiss. 1864, p. 261 ; and in Med.-chem. 

 Untersuch. p. 523 (1870). 



3 M. Nencki and N. Sieber, Monatsh. f. Chem. 9. 115 (1889). See also Schmiede- 

 berg's Arch./, experiment. Path. u. Pharm. 24. 430 (1888). 



4 A. Schulz, Arch.f. (Anat. u.) Physiol. 1904, Suppl. p. 271. 



5 Hoppe-Seyler-Thierfelder, Handbuch d. physiol. u. pathol. Analyse, 1903, p. 282 

 (seventh edition). 6 P. P. Laidlaw, Journ. of Physiol. 31. 465 (1904). 



