422 Prof. Baly and Mr. Tryhorn on Light 



and the centres o£ the two bands are then at 1/A, = 3066 and 

 3874 respectively. In this case, since the concentration is 

 the same for both bands, it is obvious that 



3066 _ 3874 



= the wave-number of the infra-red band 

 at the concentration V — 1280. 



Since x and y are two integers the only possible solution is 



3066 3874 • 1 . 



It follows that the wave-number of the less refrangible band 

 in alcoholic solution is 19 x v x , and that the wave-number of 

 the more refrangible band is 24 x v x . The true value of 

 v x for salicylaldehyde vapour must therefore be 



3978 



24 



= 165-75. 



In the third and fourth columns of Table III. are given 

 the wave-numbers of the infra-red band and the corre- 

 sponding wave-lengths calculated on the basis # = 19. In 

 fig. 1, curve II. is shown the relation between v x and the- 



Fig. 1. 



•^325 



•£324 



| 323 



£322 



321 



320 



319 

























... 











































































































/ 



/ 































\ 





, 



M 

































\ 





/ 























































































































































/ 



I 1 



































/ 





1 



! 





















1 

































i 

















































































.. 











1 









i 











1 



12 3 



7 6 9 10 II 12 13 14 15 16 17 



LogV. 



concentration from the values given in Table III. The 

 dotted portion of the curve is extrapolated to show that by 

 analogy with the corresponding pyridine curve, the calcu- 

 lated value of 165*75 is very probably correct. The general 

 conclusions, therefore, drawn from pyridine are thus fully 

 confirmed by salicylaldehyde, namely, that on the addition 

 of a solvent the absorption band first shifts towards the red> 



