EVAPORATION AND CONDENSATION 



317 



The times of relaxation for various substances as calculated by this 

 equation are given in the fourth column of Table III. The data used in 

 the calculation, // and o, are given in the second and third columns. The 

 values of a were calculated from the density p and atomic weights A given 

 in the fifth and sixth columns. For such substances as calcite and glass A 

 was taken to represent the average atomic weight of all the atoms in the 

 substance. The seventh column gives t the natural period of oscillation of 

 the atoms of the substance. 



TABLE III 



This natural period is the reciprocal of v the atomic frequency (Eigen- 

 schwingungen). The atomic frequency may be calculated in any one of a 

 half dozen different ways ^^ with substantially similar results. The values 

 given in the table have been obtained from the compressibilities K by 

 means of Einstein's ^- equation 



X =i=3.5X io-M*p*K*. 



(34) 



Objections may be raised against the use of this equation for the cal- 

 culation of the periods of oscillations of the atoms of compounds, but it is 

 not likely that the order of magnitude of the result will be in error. Koref ^^ 

 calculates by other methods that in a rock salt crystal the frequency of 

 the sodium atom is 6.8 X lo^^, and that of the chlorine is 5.5 X lo^^ fhe 

 atomic frequency calculated from the value of T in Table III is 4 X lo^^ 

 which is not greatly different from Koref's results. 



^^ Harkins and Hall., Jour. Amcr. Chcm. Soc, 38, 207, 1916. 

 ^^ Ann. Phys.. 34. 170, 1911. 

 ^^ Phys., Ztsch., 13, 186, 1912. 



