122 



P. George, J. Beetlestone and J. S. Griffith 



applied magnetic field, necessitates corrections of the magnitude quoted 

 above (Griffith, 1958). 



The Visible Region, 480 to 650 w// 



Using the extinction coefficients for ferrimyoglobin and ferrihaemoglobin 

 hydroxide given in Fig. 10, and without applying any corrections, the 



650 



600 



550 



500 



A(m;j) 



Fig. 13. Visible spectra for the high and low-spin hydroxides calculated from 



the data for ferrimyoglobin and ferrihaemoglobin hydroxides. No A or £mM 



corrections: Hi = 1-lA, fih = 5-92. 



absorption curves in Fig. 13 are obtained. The remarkable extent to which 

 these spectra show the predominant features expected of high- and low-spin 

 complexes is immediately apparent. 



Reference to the spectra for the fluoride and cyanide derivatives in Figs. 5 

 and 6 shows that the extinction coefficients are so very similar for myoglobin 

 and haemoglobin that no correction on this account need be considered. 

 On the other hand, the absorption bands of the ferrimyoglobin derivatives 

 are all displaced toward longer wavelengths by a few millimicrons relative 

 to haemoglobin. Calculations allowing for a 2 m/ti, 3 mw and 5 m,M displace- 

 ment have been carried out with the following results. The main absorption 

 bands are little affected either in position or in intensity, as shown by com- 

 paring the data in lines b, c and d with those in line a of Table 4. However, 

 minor improvements in the spectra are obtained. The extinction coefficients 

 for the low-spin form take on small positive values, e^^i «:; 1, in the range 



