﻿226 Prof. E. C. C. Baly on 



bands as measured by Coblentz *. Four of the calculated 

 bands were observed by Coblentz, and as can be seen the 

 agreement is exceedingly good. 



Table I. — Benzene. 



o x i" 

 Angstroms. 



1/X. 



VX. 



Mean v x . 



Infra-i 



Calc. 



eel bauds. 

 Obs. 



2670 



3745 



310 





1 3-23 ft 



325 ft 



2630 



3802 



253 



249 



408 





2590 



3861 



194 





545 





2523 



3963 



92 



925 



1081 



10-78 



2466 



4055 













2411 



4148 



93 



92-5 



10-81 



10-78 



2360 



4237 



182 





5-50 



541 



2335 



4282 



227 





4-40 



4-40 



2326 



4299 



244 



249 



4i»8 





2279 



4388 



333 





3-00 





On the other hand, there are altogether sixteen absorption 

 bands shown by benzene between 3*0 fju and 15 /a, which is 

 the limit reached by Coblentz; and the question at once 

 arises as to whether each of these gives rise to a correspond- 

 ing line or pair of lines in the ultra-violet band when com- 

 pounded with the central vibration 1/X = 4055. The complete 

 list is given in Table II., and as can be seen every single 

 infra-red band gives a pair of ultra-violet lines, except the 

 band at 3*23 ft, which only gives one line on the red side of 

 the centre. 



Certain of the calculated infra-red bands have not been 

 observed by Coblentz, and they are included in the table 

 because the corresponding ultra-violet pairs were given by 

 Hartley as the heads of the ultra-violet band groups, and 

 therefore the presumption would be in favour of these being- 

 important lines. Of course it is perfectly possible that the 

 corresponding infra-red bands were missed by Coblentz 

 owing to their being very narrow, but there is also another 

 possible explanation. It must be remembered that only 36 

 out of the 200 benzene absorption lines are accounted for in 

 the above table. It would seem likely that that in addition 

 to the combining of the short-wave infra-red frequencies with 

 the central frequency 4055, there is also coupled with these 

 the rotation vibration of the molecules. If this were so 

 then the probable result would be the existence of several 

 * Publications of the Carnegie Institution, Washington, No ; 35 (1905). 



