Forces of Attraction between Atoms and Molecules. 



807 



where M is a constant, which is the same for all gases at the 

 s;ime temperature and pressure. This equation may be used 

 to calculate the relative coefficients of: diffusion of gases into 

 one another. 



Table VI. contains the coefficients of inter-diffusion of a 

 number of gases taken from Winkelmann's Handbuch der 

 Physik, Warme, p. 759. The third column in the table 

 contains the coefficients calculated by means of the above 

 equation. The calculated coefficient for N 2 — C0 2 has been 

 put equal to the experimental and the others reduced cor- 

 respondingly. The agreement between calculation and ex- 

 periment, although not very good, is sufficiently close to 



show that the law of attraction ^ 2 between two 



molecules is approximately true. x 



Table VI. 



Name of Gases. 



Observed coefficient 

 of diffusion. 



Calculated coefficient 

 of diffusion. 



N o 0— CO- 



•089 

 •142 

 •159 

 •11)0 

 •161 

 •180 

 •480 

 •556 

 •642 

 •722 



•089 

 •125 

 •151 

 •125 

 •160 

 •116 

 •655 

 •723 

 ■904 

 •871 



Afr -CO, 



Cfr 2 — C0 2 



CO — C0 2 



0., — C0 2 



CO — 2 



jf 2 _sOo 



If _co 2 



Ha -CO* 



H 2 — 0„ 





The quantity K we have seen is only approximately a 

 constant; therefore, even if the inverse filth power law were 

 exactly true, a good agreement could not be expected since 

 the values of K for different gases are equal to one another 

 only at corresponding states, and have different values there- 

 lore at the same temperature. Remembering this, and 

 considering the extremely complicated nature of the process 

 of diffusion, the agreement between observation and calcu- 

 lation by a formula of such simplicity is perhaps better 

 than can be expected. 



Inferior Limit of the Distance of Separation of two 



Molecules duriny Collision. 



AVhen a molecule collides with another the kinetic energy 

 of either must be greater than the potential energy when 

 they are in contact due to their attraction, for otherwise they 

 would remain adhering to one another. The diameter of a 



