Spectra and Redox Potentials of Metalloprophyrins and Haemoproteins 79 



cn\ 



( Fe^— P) log K= +10-94 



Fig. 1 . Pyridine and cyanide haemochrome equilibrium constants in 

 aqueous solution at room temperature. 



log K 7 =+6-34 



CN\o 



F|i—PJ|ogKg:+ 14-45 

 Py/ 



logK8=-l-77 



Fig. 2. Pyridine and cyanide ferrihaemochrome equilibrium constants in 

 aqueous solution at room temperature. 



Figs. 1 and 2 



Log K refers to the logarithm to the base ten of the formation constant in the 



direction of the solid arrow calculated from the data of Clark et al. (see text). 



The subscripts 1 or 2 outside the brackets refer to the monomeric or dimeric 



nature of the complex. 



Clark, W. M. e/a/.,y. Wo/. C/j^/w. (1940). 135,543; (1940). 135,623; (1940). 135, 

 643; (1947). 171,143; (1952). 198,33; (1953). 205,617. 



