Light Absorption and Fluorescence. 51ft 



Table II. 

 Sub-groups in the Ultra-violet Band Group of Benzene. 



I. R, Bands. 



1/\=40o0±iv'1/\-18. 



3-25/x 



4-4 



49 



5-43 



9-78 



Centre 



11-8 

 5*45 

 4-4 

 3-25 

 218 



308 

 227 

 204 

 184 

 102 







85 

 184 

 227 

 308 

 460 



3742 



3823 

 3846 

 3866 

 3948 

 4050 

 4135 

 4-31 

 4283 

 4358 

 4510 



3724 

 3805 

 3828 

 3848 

 3930 

 4032 

 4117 

 4216 

 4265 

 4340 

 4492 



Wave-lengths of Su 



b-groups. 



X cale. 



X obs. 



X OD3. 



•Hartley. 



2685 



2685 



2682 



2632 



2630 



2630 



i 2612 





2614 



2599 



2600 



2600 



2545 



2540 



2539 



2480 



2482 



2480 



2429 



2429 



2426-5 



2372 



2376 



2376 



2345 



2344 





2304 



2300 





2328 



2230 





is the benzene band due to the basis constants 37 and 4*0, 

 as already discussed under benzene. Now, as was shown 

 above, water exhibits two absorption bands at 6*25 and 6p 

 due to the basis constants 2'5 and G'G, and of these bands the 

 latter is by far the stronger. On the other hand, the wave- 

 number of 6*25yu,, 160, is a whole multiple of each of the 

 three basis constants 4, 2\5, and ti'6, for 



160 = 40 x 4 = 64 x 2'5 = 24 x G'6. 



Obviously, therefore, this band in the case of phenol will be 

 enormously enhanced, since its frequency is a multiple of the 

 basis constants of both water and benzene. It is thus clear 

 that the three phenol bands, of which the one at 6*25 fi is 

 the strongest, can be explained by the basis constants of 

 water and benzene, for the band at 2'97/a is no doubt the 

 same as the water band at 3'Oyu, already dealt with. Of the 

 three great infra-red bands of phenol, therefore, one is due 

 to the basis constants of benzene alone, one due to the 

 basis constants of water alone, while the third is due to 

 those of water and benzene combined. From these facts 

 the ultra-violet absorption lines of phenol can at once be 

 calculated, since the central line of the ultra-violet band 

 group must be a multiple of the frequency of the band at 

 3'0/Ip or that at 6*25 //,, more probably the hitter since it is 

 due to the basis constants of both water and benzene. Now 

 in neutral solution, phenol shows two ultra-violet band groups 

 anil one fluorescence maximum. In alkaline solution it also 



