and the Properties of Liquids. 577 



On equating the two values of /ul indicated we obtain an 

 expression for «'". 



An infinite number of expressions for tc'" can thus be 

 obtained ; and we cannot therefore determine the form of the 

 arbitrary function in the law of attraction from one of them. 

 This remark applies also to the other constants that will be 

 considered. 



The general equation for the internal heat of evaporation 

 deduced from the law of attraction between molecules is 



where A! and A 2 are each the same for all liquids at corres- 

 ponding states *. At the absolute zero this equation becomes 



where Aq is the value of A 2 and A " that of A 2 at the 

 absolute zero. Since the first of the above equations may be 

 written 



we have 



T _ T (A^/3-A^s) _ 



(A V»-Ao'V»j&«» " * °' 



where rj is the same for all liquids at corresponding tempera- 

 tures. To obtain another value for rj let us take the equation 



L = C(p 1 2 -p 2 2 ), 



where C depends only on the nature o£ the liquid f. At the 

 absolute zero we then have 



iii" — n 2 

 and therefore 



T _ (ni 2 -n 2 2 ) T 



-L/— p L, = r)Li . 



On equating these two expressions for rj an expression for 



in terms of n 1 and n 2 is obtained. 



* Phil. Mag-. May 1910, pp. 794-795. 

 t Phii. Mag. Oct. 1910, p. 678. 



