THE CHEMICAL CONSTITUTION OF H^LMIN 517 



It combines with 2 molecules of hydrobromic acid ; in this reaction the 

 firm combination of the iron is loosened and the molecule undergoes an 

 alteration probably consisting in a change in the mode of combination of two 

 of the nitrogen atoms. The addition compound is hydrolysed and converted 

 into haematoporphyrin, two bromine atoms being replaced by two OH groups. 

 Haematoporphyrin is a dihydroxy-dibasic acid : 



Oil 



X 



COOH 



In the conversion of haematoporphyrin into haemoporphyrin by heating with 

 methyl alcoholic potash in pyridine solution reduction takes place as well as 

 loss of water : 



CggHggOg^ + H<J = CggHggO^ + aHjjO. 



Haemoporphyrin is also a dibasic acid : 



.COOH 



4 \COOH. 



By heating it with soda lime, it loses 2 molecules of carbon dioxide and is 

 converted into aetioporphyrin : 



C 3 iH 36 N 4 . 



Haemin is reduced by methyl alcoholic potash in pyridine solution to meso- 

 haemin. Mesohaemin is converted by hydrobromic acid through addition 

 products to mesoporphyrin which is a dibasic acid isomeric with haemopor- 

 phyrin. 



Aetioporphyrin (p. 523) has probably the formula : 



HC = CH 

 CH, H 





Aetioporphyrin, C 31 H 36 N 4 . 



The probable formula of haemoporphyrin is derived from this by introducing 

 two COOH groups into two of the ethyl groups ; 



HC=CH 



HOOC-CH 9 -CH 9 f=< 



O NH 



CH 



CH 



H 2 - CH.y COOH 

 CH 



Haemoporphyrin, C 83 H 36 O 4 N 4 . 



Haematoporphyrin contains two hydroxyl groups ; one of these is attached to 

 the third ethyl group, the other to the vinyl grouping, which no longer forms 

 a cyclobutene ring : 



