148 



David L. Drabkin 



C0CI2 (Fig. 4), a mean value of la"- is readily obtained from several points 

 along the left contour of the determined absorption curve. In other cases 

 simultaneous equations are useful in deriving appropriate values, aided by 

 suitable processes of curve fitting, details of which cannot be supplied here. 

 Having settled on values for 2a^ and /c, values for y are calculated with 



Fig. 4. The graphic-mathematical analysis of the absorption spectrum curve of 

 C0CI2 in concentrated HCl (Drabkin, 1940). The continuous solid line with 

 multiple inflections is the absorption spectrum obtained by Erode (1928), and the 

 open circles represent summational points obtained by his method of analysis (see 

 text). The individual curves, numbers 34 to 41, were obtained by the writer's 

 method of analysis with curves of the normal frequency form. The black dots 

 show the summation of these curves, expressed by the equation inserted in the 

 figure. For 734 to J41 the values of k are 0-19, 1-20, 0-75, 1-08, 0-55, 0-80, 0-57, 

 and 0-19. The corresponding values for Id^ are 102-0, 102-0, 102-0, 97-5, 93-8, 



92-3, 27-2, and 66-2. 



equation (2) to yield the curves. Experience will suggest labour- and time- 

 saving devices in this type of graphical analysis. It should be clear that the 

 choice of spectral interval in terms of i^ X 10"" determines the locations (at 

 equal frequency distances from each other) of the values of a. 



It is of interest that the analysis of the absorption spectra of complex 

 molecules into component bands of the shape of normal frequency curves 

 makes it possible to express the spectra in relatively exact mathematical 

 terms. This cannot be done with the earlier successful analytical procedure 

 used for KMn04 and CoCU. Hence it was desirable to test the applicability 

 of the new method by the analysis of the spectra of the simpler molecules. 

 Figure 4 and its legend give the analysis of the spectrum of CoClg, and the 



