250 



Mr. S. S. Richardson on Magnetic Rotary 



It will be seen that since the mean dispersional period 

 '1815//, is considerably greater than the mean o£ the values 

 obtained above from formula (9), Meyer's equation cannot 

 apply strictly in the case of benzene. A similar remark 

 applies to the liquids water, metaxylene, naphthalene bromide, 

 and carbon bisulphide. 



Martens * deduces a formula for benzene in which 

 a = '4528, a^'7264, c=0, and A^-1745. The differences 

 for this formula are given in the last column above. 



Prof. Baly associates the central line of the absorption 

 spectrum of benzene vapour (*2466) with the infra-red band 

 observed by Goblentz at 2'49 u, the ratio being nearly 1 : 10. 

 In this connexion it is worth notice that the principal disper- 

 sional period deduced above from the magnetic rotation 

 •1902 //,, is almost an exact snbmultiple of 2*49 /x, the ratio 

 being 1 : 13. 



The absorption bands of benzene in the near ultraviolet 

 with a centre at *2466 /x have very little effect on the 

 dispersion or magnetic rotation. Introducing a term for 

 this band, I find that the constant k is only 1/740 of the sum 

 of the remaining constants. The absorption is here clearly 

 due to a comparatively small number of electrons. A 

 probable explanation being that the period *2466 is only 

 acquired by one or more electrons in the molecule at com- 

 paratively rare intervals, due to an accidental distortion of 

 the molecule through collision. M. Henri |, from photo- 

 metrical measurements, finds that in acetone only one 

 molecule in 36 is effective in producing the characteristic 

 bands of this substance, and Baly and Try horn have recently 

 obtained a similar result for aniline. 



m. Xylene. 

 The observations w r ere conducted in the same manner 



us 



Obs. 



\xio 4 . 



£xio 6 . 



»90' 



» 0XlO u . 



a 



•6708 



5-416 



1-4914 



3634 



b 



•5893 



7-210 



1-4965 



3-747 



c 



•4958 



10-84 



1-5061 



4014 



d 



•4529 



1351 



1-5131 



4-194 



e 



•4046 



1819 



1-5242 



4-538 



/ 



•3631 



24-72 



1-5381 



5-014 



1 



Ann. d. Phys. ((5) p. 603 (1901). 

 Phys. Zeits. p. 515 (1913). 



* Ann 



t 



