Chemical Attraction between Atoms from Physical Data. 99 



where b is a numerical constant. The equation for the 

 Liient heat then becomes L=E(/o^_^), where E is equal to 



^ — Y% }i • This equation we have already deduced pro- 



viously and found to agree well with the facts'*. 



If we give the arbitrary function the form ul— J , where 



u is a numerical constant, we obtain a very convenient 

 expression for the surface tension. The attraction between 



two molecules is then given by -^ , where 



K 3 = u4@ \A%) 2 = "(™) 2 (2 VmJ 



2 



P.- 



an expression for the attraction we have already used in this 

 paper. This gives for the surface-tension the formula 



\ = ¥( Pi - P2 )\ where F = ufi Vm i\\ 



\ mp c J 



In Table IV. (p. 100) the values of F are given for temperature 

 intervals of 10° for a number of liquids. It will be seen that 

 they are approximately independent of the temperature over 

 the ranges of temperature given in the table. If the general 

 law of attraction is true, the value of F should be equal to 



^ v m i j > This is found to be the case, as is shown by 

 mpc / 

 Table V. (p. 101), the value given to u being determined by 

 the method of least squares to be 32*96. 



If the attraction between two molecules is taken to be 



XT" 



given by — ° , where K 5 depends only on the nature of the 



liquid, then according to the general law of attraction 



/ p \l/3 



K5 = Si( — j (^ V'»i) 2 ) where S x is a numerical. If this 



constant expression for the attraction is substituted for 



<j>(z)(Z Vm-tf in the equation f for the intrinsic pressure p n 



Fp 1,s — 

 of a liquid, we obtain p n =—~(Z y/m x ) 2 p 2 , where F is a 



numerical constant. Now van der Waals has proposed the 



* Phil. Mag. Oct. 1010, pp. 686-687. 

 t Phil. Mag. Oct. 1910, pp. 666-667. 



H2 



