Law of the Rectilinear Diameter, 



417 



The values of k for a series of liquids for which Maxwell's 

 relation K = n 2 approximately holds is given in Table I. 

 below. 



Table I. 



Liquid. 



Benzene 



Carbon bisulphide 

 Carbon tetrachlorid 



Cymene 



Toluene 



Thiophene 



Turpentine 



Naphthalene 



Xylene-o 



K. 



a. 



T c . 



k. 



23 



262 



225 



2-25 



2375 



2-76 



23 



27 



2-567 



•001176 



•00114 



•001186 



•000895 



•00107 



•0011 



•0009 



•000747 



•00095 



563 

 575 

 558 

 652 

 594 

 590 

 649 

 741 

 631 



2-499 



2-291 



2-56 



2-68 



2-5 



2-3 



2-59 



2-498 



2-432 



Diff. from 

 Mean. 



-•001 

 -•201 

 + •06 

 + •18 



-•2 



+ •09 



-•002 



-•068 



Mean Yah 



2 5 



These liquids were selected quite at random from Landolt 

 and Bornstein's tables, and the value of k comes out with 

 very satisfactory consistency. The mean value 2*5 is regarded 

 for the remainder of the paper as the value of the ratio of 

 the volume at the absolute zero of temperature to the real 

 volume occupied by a given number of molecules. 



2. Inductive Power and Molecular Inductive Power. 



The Lorenz-Lorentz expression 



n 2 -l 1 n 2 -l M 



n* + 2'd n 2 + 2'~d 



are known as the " refractive power " and the " molecular 

 refractive power " respectively, M being the molecular 

 weight. It seems appropriate, therefore, to give the names 

 " Inductive Power " and "Molecular Inductive Power" 

 to the corresponding expressions when K is used. 

 From equations (1) and (4) 



K-l 1 1 



K + 2 ' d 



2*kT c 

 1 



2JX 



al c 



(6) 



