DIELECTRIC PROPERTIES OF INSULATING MATERIALS 667 



curves obtained by plotting (41a) and (416) for suitably adjusted 

 values of the constants only places the type of mechanism to which 

 the observed dispersion can be attributed within the rather large 

 catagory which includes at least the seven types of mechanism listed in 

 the table. Data showing the dependence of (^o — ^co)/p on temperature 

 allows a further specialization of the processes which could account 

 for the observed behavior; and of course a number of possibilities can 

 be discarded on general grounds of physical improbability . And 

 finally, agreement of the constants calculated from dielectric measure- 

 ments with the values calculated from independent estimates of the 

 sizes and other characteristics of the molecules or other elementary 

 units which contribute to the polarization provides the most convincing 

 evidence of the nature of the polarization. Such agreement is fre- 

 quently obtained in the application of the Debye theory to gases and 

 liquids. 



The characteristics which can be deduced from equations (41a) and 

 (416) without substituting for the constants theoretical expressions, 

 such as those given in Table I, are of considerable value in interpreting 

 electrical measurements upon dielectrics. It may be convenient to 

 describe these as the general characteristics of anomalous dispersion, 

 distinguishing them thereby from the special characteristics peculiar 

 to particular kinds of dielectric polarization which share the property 

 of producing anomalous dispersion in the radio and power range of 

 frequencies. 



Appendix 



The following list contains the definitions of the quantities which 

 appear in Table I : 



ei, €2, 7i, 72 are respectively the dielectric constants and conductivities 

 of two materials designated by subscripts 1 and 2, the unit 

 of conductivity being such that 7 = 367r X 10'^ X, where 

 X is in (ohm-cm)~^ 

 eo, Coo are respectively the dielectric constant at the lower and 

 upper extremities of dispersion curves; they are called the 

 zero-frequency (or static) dielectric constant and the 

 infinite-frequency dielectric constant, 



L is the number of molecules per unit volume, 



y] the viscosity of a liquid containing polar molecules, 



k Boltzmann's constant, 



T the absolute temperature, 



IX the permanent electric moment of a polar molecule, 



