880 Dr. R. D. Kleeman on the Effect of the 



(6) then give 



i— * — U 2 i ^ Jr^lirjr^ 



( 1 + c 2 h-c 3 + . . . ; ^ 



But the attraction between two molecules is probably not 



given by an expression of the above form. c n is therefore 



probably a function of x as well as of n and m. But it will 



obviously not vary very much with x, since the law of 



attraction could always approximately be represented by an 



expression of the form given. The variation of the values of 



c n with x, it will be seen, affects the value of the function X 



very little on account of its form. It follows therefore that 



equation (9) very approximately represents the facts, and 



that the value of X can be determined with fair accuracy 



from a form of the law of molecular attraction which is 



approximately correct. 



In previous papers * it was shown that the law of attraction 



k 

 between two molecules is approximately given by-^, where 



z denotes their distance of separation and k a quantity which 

 is constant at constant temperature. This law may therefore 

 be used to calculate the value of X. The calculations will be 

 facilitated by the following considerations. Let a 1 denote 

 the work done against the attraction of the molecules in the 

 plane ah on moving the molecule situated in the slab B at a 

 distance x from the zero of coordinates to an infinite distance 

 from the plane ah. Let a 2 denote the work done in moving 

 the molecule situated at a distance 2x from the zero of co- 

 ordinates to an infinite distance from the plane, and a 3 the 

 work done on transporting the molecule at a distance 3^, &c. 

 The total work A x done on moving the molecule at a distance 

 x to infinity against the attraction of all the molecules in the 

 slab A is therefore given by 



Ai = (q 1 + a 2 + a 2 + . . . a n ). 



The total work A 2 done on moving the molecule at a distance 

 2x to infinity against the attraction of all the molecules in the 

 slab A is therefore given by 



A 2 =(a 2 + a 3 + a 4 + . . . a n ) ; 



* Phil. Mag. May 1910, pp. 795-807 ; Proc. Camb. Phil. Soc. vol.xvi. 

 pt. 7, pp. 586-587. 



