﻿Relative Dimensions of Molecules. 



555 



It is, perhaps, worthy of note that the case where the ratio 

 of densities differs most from unity is that where argon is 

 involved, and that argon has, from the point of view of the 

 periodic arrangement of the elements, an abnormally high 

 atomic weight, the effect of which is to give the above - 

 mentioned ratio a low value. 



Another point of interest in connexion with the molecular 

 dimensions of these two groups of gases may be based upon 

 the interpretation of Sutherland's constant C previously 

 referred to. This constant is a measure of what Sutherland 

 called iC the potential energy of two molecules in contact with 



one another," but which would be better defined 



as 



the 



work done against attractive forces in separating to an 

 infinite distance two molecules originally in contact." 



The following table shows the relation which exists between 

 these quantities of work for the pairs of gases with which we 

 have previously dealt. 



Table III. 



Pair of Grases. 



Chlorine : Argon ... 

 Bromine : Krypton. 

 Iodine : Xenon 



Values of C. 



Eatio halogen). 

 C (inert) 



325, 142 

 460, 188 

 590, 252 



23 

 2-4 

 23 



The numbers in the last column are constant to an extent 

 oertainly within the accuracy with which the values of C are 

 known. We may therefore say that the work done in sepa- 

 rating to a great distance two molecules of a halogen gas 

 originally in contact is 2*3 times as great as for two molecules 

 of the corresponding inert gas. 



The attempt to go further and investigate the law of force 

 upon the basis of these figures has been made by the author, 

 but has been found to lead to inconsistencies. One is driven 

 to the conclusion that a single law of force depending in a 

 definite way on mass and distance only cannot apply to 

 molecules differing widely in internal constitution. 



