﻿Light Absorption and Fluorescence. 225 



Some preliminary support for the idea is gained from the 

 fact that benzene exhibits nine absorption maxima which are 

 obviously arranged symmetrically around a central position. 

 This is also the case with several other compounds. 



Again it follows that exactly the same structure should be 

 found in the case of the fluorescence bands of the same sub- 

 stances. Finally, from what was stated in my previous 

 paper, the central line of the fluorescence and absorption 

 maxima should be consecutive multiples of a whole number 

 which equals the frequency of one of the infra-red bands. 



I have calculated the values of the ultra-violet absorption 

 lines of one or two compounds, and find that they form in 

 each case a series of pairs symmetrically distributed about a 

 central line, and that the frequency of every infra-red band in 

 the short-wave region has a corresponding line or pair of lines 

 forming part of the structure of the ultra-violet absorption 

 band. In short, the application of the Bjerrum conception 

 to both ultra-violet and fluorescence bands is completely 

 successful, and moreover the conclusions in my previous 

 paper are entirely confirmed. This may be seen from the 

 following. 



Benzene. 



Hartley* investigated the ultra-violet absorption band of 

 benzene and published measurements of the wave-lengths 

 of the component lines, which amount in number to about 

 90. He showed that these fine bands or lines seem to form 

 ten groups, each with a well marked head. He gave the 

 wave-lengths of these heads as 2670, 2630, 2590, 2523, 

 2466, 2411, 2360, 2335, 2326, and 2279 Angstroms. The 

 values of 1/A, for these, expressed in four figures, are 3745, 

 3802, 3861, 3963, 4055, 4148, 4237, 4282, 4299, and 4388, 

 respectively. Now it is obvious that the first four and the 

 last five of these can be symmetrically distributed about the 

 fifth with frequency (1/X) of 4055. The following table 

 shows the arrangement of the ten bands and the values of 

 the frequency differences. 



In the third column are given the frequency differences 

 between each line and the central line, and in the fourth 

 column the means between the two values where such 

 exist. The values of l/v x or the wave-lengths of the infra- 

 red bands are given in the fifth column, while in the last 

 column are to be found the wave-lengths of the absorption 



* Phil. Trans, ccviii. A. p. 4 75 (\^>. 

 Phil. Mag. S. 6. Vol. 29. No. 170. Feb. L915. Q 



