﻿Light Absorption and Fluorescence. 237 



Table XII. — Naphthalene fluorescence (Dickson). 



1/X. 





Calculated 



V£. 



Infra-red bands. 



2714 



306 



327 ^ 



2761 



259 



3-86 



2808 



212 



472 



2855 



165 



606 



2902 



118 



8-48 



2949 



70-5 



14-2 



2996 



235 



42-6 



(3020) 







3043 



235 



42-6 



3090 



70-5 



14-2 



3138 



118 



8-48 



3185 



165 



6-06 



3232 



212 



4-72 



3279 



259 



3-86 



3326 



306 



327 



The absorption of naphthalene vapour has been investigated 

 by Purvis, who finds that the bands shown by the alcoholic 

 solution are not resolved into fine lines. It is necessary, 

 therefore, to make use of the solution spectrum of naphtha- 

 lene for the present comparison. This spectrum has been 

 measured by several observers*, and Mr. F. C. Guthrie, in my 

 laboratory, has kindly repeated the observations, using the 

 new Hilger ultra-violet spectrophotometer, the accuracy of 

 which far exceeds that of the old method of qualitative 

 measurement. 



In Table XIII. the first column shows the values of v.. 

 obtained from the fluorescence bands and given in Table XII. 

 The second column contains the calculated frequencies of 

 the absorption bands, while the corresponding wave-lengths 

 appear in the third column. In the fourth column are given 

 Mr. Guthrie's measurements. 



The agreement between calculated and observed values is 

 exceedingly good in view of the fact that there are no infra- 

 red measurements against which the frequency differences 

 (v x ) can be checked. Certain of the calculated absorption 

 bands do not appear in the solution spectrum, and the broad 

 band at A,= 2965 does not seem to divide. One more absorp- 

 tion band has been observed at X = 2G 70 beyond those that 

 have their counterpart in the fluorescence spectrum. It 



* Hartley, Trans. Chem. Soc. xxxix. p. 153 (1SS1) ; xlvii. p. 6&*5 

 (1885). Baly and Tuck, Trans. Chem. Soc. xciii. p. 1902 ( 1 908). Purvis, 

 Trans. Chem. Soc. ci. p. 1315 (1912). 



