Changes in Dielectric Constants and in Volumes. 63 



We shall call the quantities represented by 1 and 3, the 

 dielectric energies. 



The change in dielectric energy when the sphere is placed 

 in the field is 



w-w _KAY 9k; \ 



For a second sphere of dielectric constant K^ and volume v^ 

 we have 





W,-W„ = ^ ( _--^_^^ -i )v^ 



Consequently the dielectric energy involved in changing the 

 first sphere into the second, if we put K^ = 1, is 



Now imagine that we are living in surroundings correspond- 

 ing to an electric field and that the energy in the space occu- 

 pied by a particular body is measured by 3. Then as we 

 produce one set of bodies from another set we can expect such 

 change in the energy of the system as is represented by 4, in 

 which the indices refer to the two sets of bodies respectively. 

 This change should be measured by a corresponding quantity 

 of some other form of energy rejected by the changing system 

 or absorbed by it ; for instance, measured by the heat of the 

 change. Whether the change from state 1 into state 2 causes 

 a rejection or absorption of heat is not predicted ; the only 

 assumption made is that the dielectric constant measures the 

 effect the body has upon the energy of the field according to 

 the laws of electric action, when placed in that field. 



Equation 4 was deduced for spheres, but since such very 

 slight changes are produced in the properties of a system by 

 moderate subdivision, we claim the same relation for all shapes. 



Let us apply 4 to vaporization, for there are enough data in 

 Landolt and Bornstein's Tabellen and elsewhere for three 

 liquids, sulphur dioxide, ammonia, and water. In this case 

 W,- W, = Q and if Stt/E; = A, we have 



where v^ is the volume in c.c. of saturated vapor produced from 

 v^ in c.c. of liquid and K2 and K^ are the respective dielectric 

 constants of vapor and liquid. 



