798 Dr. R. D. Kleeman on the Nature of the 



law being probably a complicated function of z and T. The 

 nature of the law will be further discussed as we proceed. 



The foregoing investigation shows that the molecular 

 attraction which gives rise to surface-tension is also respon- 

 sible for the internal heat of evaporation. The fact that we 



may replace Sx/wh by %v, the sum of the valencies of the 

 atoms in a molecule, suggests that it is also the force operating 

 in chemical combination. We may suppose, as is done by 

 chemists, that each atom contains a number o£ cells each of 

 unit valency. A cell will thus attract another with a force 



equal to — o • 



The study of chemical combination has shown that the 

 avidity of an atom decreases with the number of atoms with 

 which it is already combined. Thus the attraction of one 

 valency cell on another depends on the presence of other 

 cells. The nature of chemical attraction thus differs from 

 that of gravitation, which is independent of all conditions. 

 The chemical attraction of a molecule would not, therefore, be 

 an exact additive property of the attractions of its atoms. The 

 slight deviations of the facts from the relations expressed by 

 the equations given at the beginning of the paper may partly 

 be ascribed to this effect. 



Chemists suppose that an atom is linked to another in a 

 molecule by the attraction of two valency cells, one belonging 

 to each atom. Therefore at least one cell of each atom in a 

 molecule is weakened as far as its attraction outside the 

 molecule is concerned. Since a hydrogen atom contains one 

 valency cell only its attraction would be much more weakened 

 by combination than that of any other atom. One would 

 therefore expect that if the value of the constant c a for an 



atom is given exactly by v mi or v when not in combination 

 with other atoms, the value of c a for hydrogen in chemical 

 combination relative to the values of c a for the other atoms 

 in combination should be less than that given by Vm^ or v. 

 This is strikingly shown by the results obtained by the writer. 

 Using the equation 



r 



the writer has in a previous paper calculated the values of 

 c a for a number of atoms. These values are quoted at the 

 beginning of this paper. Later in the paper the writer 

 pointed out that these values give a somewhat better agree- 

 ment with the facts than the values given by s/m x or v 



