Forces of Attraction between Atoms and Molecules. 801 



and m 2 the chemical energy is proportional to ( \/"*i + V^'a)* 

 Now the latter expression is greater than the former, as is 

 at once evident when both expressions are squared, and an 

 increase of chemical energy of attraction has therefore taken 

 place under these conditions. Part of this energy must be 

 derived from the work done in separating the atoms. 



If the gravitational attraction of an atom on another cor- 

 responds to a quantity of energy proportional to the attraction 

 exerted it must be of infinite magnitude, and the factor with 

 which it must be multiplied to give the attraction must be 

 infinitely small. The decrease of energy when two atoms 

 are brought near to one another is then infinitely small in 

 comparison with the energies contained by the atoms, and 

 the attractive force of each atom would therefore not be 

 appreciably diminished, i. e. the attraction of one atom would 

 not be influenced by that of another, as we know from 

 experiment is the case. 



The heat of formation of a molecule in the gaseous state 

 decreases slightly with rise of temperature. This may be 

 due to a decrease of the force of attraction caused by the 

 rise of temperature. The force of attraction between two 

 molecules is thus probably affected in two ways, viz. (1) by 

 the temperature*, (2) by the vicinity of other molecules. 



The absolute value of K in the expression — ^ 5 — — giving 



the attraction of two molecules on one another when separated 

 by a distance z, is an important quantity and will now be 

 determined. We have 



" " L JO v — —oo u=-x, »=1 * 



+ (2 v'm,) ! -T tit"? [<*>(*) -(n + u>)l +4 T ["+(*)- (" + «") l«=o }'*»> 



where z = x a */ { [n + w) 2 + u 2 4- v 2 } .• 



If -g is substituted for <£(~) the equation becomes 



L (S^mO 2 ? r '5- v ^° w =°° (n + w)dn 



2 = —^— «SJ, ,=-. JL. *, {(n + wy+u* + v*l* 



* But since the temperature of a gas is a measure of the kinetic 

 energy of the molecules it is difficult to see how it can affect their forces 

 of attraction. 



Phil. May. S. 6. Vol. 19. No. 113. May 1910. 3 F 



