906 Dr. R. D. Kleeman on the At traction Constant of a 



cannot be tested directly. There is some indirect evidence, 

 however, supporting this supposition. Thus the attraction 

 constant ^^/m ly denoting the sum o£ the square roots of the 

 atomic weights of the atoms of a molecule in the law of 



attraction - & (2<v/ w i) 9 between molecules of the same kind, 



z' 



may be replaced by 2r, the sum of the maximum valencies 

 of the atoms of a molecule. The quantity K in the above 

 expression is the same for all substances at corresponding 

 temperatures, and may therefore be a function of the ratio 

 of the temperature of the molecules to the critical tempe- 

 rature, and the ratio of z — the distance of separation of the 

 molecules — to their distance of separation at the critical 

 temperature. Its correct form was not indicated by the 

 Investigation mentioned: a later investigation* showed, 

 however, that it must be principally a function of the 

 temperature. 



If the force of attraction producing chemical combination 

 is that given by the above law, we should expect that further 

 relations of the quantity ^\/m l of a substance with its 

 chemical properties exist. The object of this paper is to 

 point out some relations of this kind. These constitute 

 further indirect evidence that the above law of attraction is 

 the onlv one operating when chemical combination takes place. 



T 



The quantitv ., of substances, where T denotes a 



" ZV m x 



given corresponding temperature, is of the greatest import- 

 ance as its properties run parallel with the chemical properties 

 of the substances. This parallelism appears in many ways. 



T 

 Thus the value of ^~ 7= tor a substance and its substitution 



2,v'»i 

 products is approximately a constant, but varies considerably 

 from one set of substances to another. This is shown by 

 Tables I. and II., using the critical temperatures t of sub- 

 stances, which by definition are corresponding temperatures. 



The tables contain also for comparison the values of —-7 -= 



for a number of other substances which are not substitution 



T c 



products. The constancy of y /— is better in some sets of 



substances than in others. It is probable that a deviation 



T c 

 of ^r~/— from constancy in a set of substances indicates a 



AV W&1 



* Phil. Mag. Oct. 1910, p. 660. 



t Thev were taken from Landolt and Bornstein's Tables, 5th edition. 



