Analysis and Interpretation of Absorption Spectra of Haemin Chromoproteins 147 



centre of distribution at are the same, y is the height from the base of a 

 point on the curve at a distance .v from the centre, k is the height at the 

 centre of distribution a (usually designated the 'mean') for a particular case 

 (in the diagrams of this figure a = 0). a, the standard deviation, is a measure 



-L_±x-0. 



-i- ± X -Q^ I 







FiG. 3. Families of normal frequency curves of the form: 



_ fi x - a)- \ 

 y = kc ^ 2a^ ^ 



The eflfect of variability in either ^ or c is shown in 1 and 2. In 3, most pertinent 

 to the present analytical assumptions, both k and a are variable. 



of the spread or variation about the centre of the individual points, over two- 

 thirds of which in such curves lie within the interval Icr and 95% within la. 

 e is the base of natural logarithms, 2-7183. 



In our application to spectra, y and k are in a units, x and a (the locations 

 of the centres of the curves or bands, assumed or deduced from the locations 

 of the maxima in the absorption data) in units of/ or v. In the construction 

 ot the curves, 2cr^ is conveniently evaluated by a rearrangement of terms 

 in equation (1). 



(.V- a)^ (3^ 



2a2 = 



loge kly 



k and y in equation (3) are derived either directly from the absorption data or 

 by adjustment for overlapping of neighbouring component curves. In the 

 case of prominent bands, as the so-called y or Soret band in the spectra of the 

 chromoproteins, or bands at the lower frequency end of spectrum as with 



