22 



STUDY OF ABSORPTION SPECTRA 



absorbs more intensely than the solvent. Just the opposite effect is 

 noted for magnesium chloride, in which case the solution absorbs less 

 intensely. The same relation manifests itself again in the case of the 

 1.25^ band, as can be seen in figure 2 and in table 7. 



The curves are plotted in all cases from the data given in the tables. 

 The heavier line indicates the transmission curve for the solution ; the 

 lighter represents that for the solvent. 



Tables 6 and 7 are plotted as curves for magnesium chloride in 

 figures 1 and 2. 



TABLE 7. Depth of cell 10 mm. Potassium and magnesium chlorides. 



Tables 8 and 9 contain the percentage transmissions for the three 

 hydrated salts, magnesium bromide, magnesium sulphate, and zinc 

 sulphate. Where the light is intensely absorbed as at 1.2/z, and the 

 depth of layer is 20 mm., the solutions are over 30 per cent more trans- 

 parent than the solvent. In the case of magnesium chloride, bromide, 

 sulphate, and zinc sulphate at the centers of both the l/i and the 1.25/i 

 bands (figs. 1 to 8) the solutions are the more transparent. This 

 difference is very pronounced in the case of the two sulphates, especially 

 with magnesium sulphate. Here the difference for the In band is 

 about 18 per cent, and for the 1.25/j, band about 20 per cent. 



