126 



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



extinction coefficients for ferrimyoglobin hydroxide by the average of the 

 values given above, namely, 1-08, gives the curves shown in Fig. 17. These 

 are now seen to exhibit the characteristic features of high- and low-spin 

 complexes. The Soret bands are at 405 m/u with e^^^ = 116, and 417 m/i 

 with Sj^^ = 104, respectively: these positions and relative intensities com- 

 pare very favourably with those for the fluoride and cyanide derivatives. 



450 



400 



350 



300 



7^(mjj) 



Fig. 17. Ultra-violet spectra of the high- and low-spin hydroxides calculated 



from the data for ferrimyoglobin and ferrihaemoglobin hydroxides. 



The absorption curve of ferrimyoglobin hydroxide has been corrected by a 



5 m/i displacement toward the red, and all extinction coefficients multiplied by 



1-08: /<j = 2-24, /<ft = 5-92. 



Furthermore, in the region 330 to 370 m/<, the low-spin form has two distinct 

 bands at about 340 and 360 m/<, whereas the high-spin form has an unresolved 

 shoulder at about 350 m/t, like the cyanide and fluoride derivatives respec- 

 tively (see Fig. 8). It is to be noted, however, that the band width of the high- 

 spin form is larger than usual, and that of the low-spin form smaller, which 

 results in the high-spin form having relatively higher extinction and the low- 

 spin form relatively lower extinction between 350 and 400 m^t. 



The Near Infra-red Region, 700 to 950 w// 



In the absence of spectroscopic data for ferrihaemoglobin fluoride and 

 cyanide in this region, it is impossible to judge at present whether any cor- 

 rection factors should be applied. However, without correction, calculations 

 based on the extinction coefficients of ferrimyoglobin and ferrihaemoglobin 



