518 Prof. E. C. C. Baly on 



The agreement between calculated and observed values 

 throughout appears thoroughly to justify the general con- 

 ception here put forward. All the absorption lines calculated 

 have not been measured by Hartley as separate lines, but it 

 is evident from his paper that more exist than those which 

 he definitely gives. Hartley records a great number of 

 narrow absorption bands which are resolved into fine lines 

 on some of his negatives and not on others. The general 

 conclusion may be drawn from the values of these bands 

 given by Hartley that other fine lines exist beyond those 

 that he specifically mentions. Grebe in his paper gives two 

 series of measurements, one of which is more accurate than 

 the other. Those wave-lengths given with five significant 

 figures belong to the former series. 



Attention has already been drawn to the very great 

 intensity of certain bands in the short-wave infra-red 

 spectrum of benzene, and it would be expected that the 

 lines in the ultra-violet corresponding to those infra-red 

 bands should be relatively stronger. The fact that the 

 ultra-violet absorption-band group of benzene consists of a 

 number of closely situated sub-groups is well known, and 

 Hartley has given the wave-lengths of the heads of these 

 sub-groups. It is very interesting to note that these heads 

 correspond to the observed intense infra-red bands in each 

 case. Messrs. A. Williams and F. G. Tryhorn have very 

 kindly measured the absorptive power of an alcoholic solution 

 of benzene with the new Hilger spectrophotometer, and the 

 measurements of the band heads are compared in the following- 

 table with those calculated from the observed infra-red bands* 

 It must be remembered that a correction must be made for 

 the effect of the solvent, this being about 18 units in the value 

 of 1/X. 



The general agreement shown in Table II. makes it very 

 clear that the sub-groups of the bands within the whole 

 ultra-violet band are due to the principal infra-red bands 

 and the combination of their frequencies with that of the 

 central line. 



Since the basis constants of benzene and of water are now 

 known, it is possible to test whether the additive relation 

 holds good in a compound of the two. For example, the 

 test may be applied to phenol in order to see whether the 

 basis constants of benzene and water are acting independently 

 in this compound. The absorption of phenol has not been 

 examined by Coblentz over the whole region from lfx to 13 /x., 

 but three very strong bands were measured by him at 2*97//,,. 

 6*25yLt, and 6'75/ul. It is fairly obvious that the last of these 



