564 LECTURE XXIV. 



The iron in hematin may be removed easily by the action of acid. A 

 product free from iron is thus obtained which is known as hematopor- 

 phyrin and is given the formula Ci6Hi 8 N 2 O 3 . Thus, for example, we 

 may allow hydrobromic acid to act upon hematin: 



C 32 H 32 N 4 FeO4-f-2 H 2 O + 2 HBr = 2 Ci 6 H 



Hematin Hematoporphyrin 



By reduction of hematoporphyrin, mesoporphyrin Ci6Hi 8 N 2 02 is ob- 

 tained, or if the reducing agent is more energetic, hemopyrrole, C 8 Hi 3 N, is 

 formed. This last substance is methyl-propyl-pyrrole : 



HC - -C CH 2 . G 2 Ii5 



II II 

 HC X/ C-CH 3 



N 

 H 



By oxidizing hematin, Kiister obtained two crystalline acids, which he 

 designated as hematinic acids. One of these is a dibasic acid with the 

 empirical formula CgHgNO^ while the other is to be regarded as the 

 anhydride of a tribasic acid, C 8 H 8 O 5 . The formation of these two hema- 

 tinic acids is illustrated by the following schema: 



=C . CH 3 , CO C . CH 3 



HN( | -- HN; n 



x CH = C . CH 2 . CH 2 . CH 3 N CO C . CH 2 . COOH 



Hemopyrrole or Methylpropylpyrrole Dibasic hematinic acid 



00 C.CH 3 



o: ii 



x CO C . CH 2 . CH 2 . COOH 

 Partial anhydride of tribasic hematinic acid. 



The last compound, by losing carbon dioxide, goes over into the anhy- 

 dride of methyl-ethyl-maleic acid, C 7 H 8 O 3 . 



If we assume that hematin is a simple substance and not a mixture, 

 and that its transformation into hematoporphyrin takes place quanti- 

 tatively according to the equation, 



C 32 H 32 N 4 Fe04 + 2 H 2 O - Fe = 2 Ci 6 Hi 8 N 2 O 3 , 



then it is very easy to go a step farther and assume that hematin is con- 

 structed of two symmetrical halves connected together by means of an 

 atom of iron. Now, as we have seen above, hematin and hematopor- 

 phyrin, by undergoing an oxidation and hydrolysis, both give rise to the 

 same acids and to the same extent. As these cleavage-products each 

 contain eight atoms of carbon, it may be safely assumed that hemato- 

 porphyrin likewise is composed of two equal parts. As was mentioned, 



