INFLUENCE OF pH 



197 



can be influenced by the oxidation-reduction process only if they are 

 concerned in formation of polymers (Section 3.3.) and if the degree 

 of polymerization is affected by the valency change. 



7.2. Influence of pH 



The earlier studies established the fact that in general both the 

 heme-hematin system and the hemochrome-hemrchrome system 

 follow the relationship:* 



= 0.06 



ApH 



The studies of Clark and collaborators showed that this relationship 

 holds for all compounds with pyridine bases above a certain pH 



bj 



10 



11 



12 



pH 



Fig. 9. Base iron coproporphyrin systems — relation of potential to pH 

 (after Vestling, 2872). 



* A later statement by Barron (18S) that the slope for the heme-hematin system 

 is given by the relationship, — A£^/^pH = — 0.06, is erroneous. 



