﻿23b* Prof. E. C. C. Baly on 



with, every single infra-red band observed by Coblentz, with 

 two possible exceptions, is represented by either one or two 

 lines in the ultra-violet absorption band, and further, the 

 agreement between the calculated and observed values of the 

 infra-red bands is remarkable. 



The general conception can be put to a very severe test in 

 the following way. Dickson found in the fluorescence 

 spectrum of naphthalene 14 well-defined maxima which are 

 very regularly arranged. In fact their frequencies may be 

 expressed by the general formula 



l/\= 3326 -47-12 Xn, 



where n is 0, 1, 2. 13. He finds small differences 



between the observed values and those calculated from the 

 formula, especially in the case of the band with the smallest 

 frequency. It would seem, therefore, that in making any 

 calculations from the frequencies, it would be preferable to 

 use the values obtained from the formula. Now the absorp- 

 tion spectrum of naphthalene in the infra-red region has not 

 been observed, and the only fact known about it is that 

 Coblentz found a band at \ = 3*25//, for a solution of the 

 compound in carbon tetrachloride. It is not possible, there- 

 fore, to check the values of frequency differences against 

 infra-red measurements. Since the fluorescence bands are 

 very symmetrically arranged, it is possible accurately to 

 calculate the frequency differences from the central line. 

 This central frequency must be a multiple of the funda- 

 mental frequency, and the next higher multiple should form 

 the centre of the ultra-violet absorption band. From this 

 new central frequency, by making use of the frequency 

 differences found in the fluorescence spectrum, it should be 

 possible to calculate the frequencies of the lines in the ultra- 

 violet absorption band. 



In Table XII. are given the frequencies of the fluorescence 

 maxima of naphthalene as corrected by Dickson, and arranged 

 symmetrically with respect to the mean frequency 1/A=3020, 

 together with the frequency differences. 



The calculated values of the infra-red bands are given so 

 that when this region is investigated, the observed values 

 may be compared. 



Now the central frequency 3020 = 302x10, and as there- 

 fore the fundamental frequency of naphthalene is 302, 

 the central frequency of the absorption band must be 

 302x11 = 3322. In order to calculate the frequencies of 

 the absorption lines, we thus use 3322 ±v x , the values of 

 vx being those given in Table XII. 



