Evolution of the Doctrine of Affinity. 511 



furnished that not only the supposed affinity, but even the 

 actually measured avidity, is an inherent property of each 

 separate kind of matter, independent of any reaction with any 

 other kind of matter, the more doubtful is the necessity. The 

 more recent investigations of Ostwald* have shown that the 

 most heterogeneous actions of acids, in influencing the chemical 

 changes of various substances, — as, for example, in decompo- 

 sing the amides, in forming the ethereal salts, in inverting the 

 sugars, and moreover in influencing the electrical conduc- 

 tivity, — are all dependent on the same constant, the affinity or 

 avidity. If the ability of acids to act remain the same in rela- 

 tion to so many different phenomena, the assumption appears 

 justified that it is caused, not by mutual action, by attraction 

 of one kind or another, but is in reality something peculiar to 

 the nature of the acids themselves. 



There might be a temptation to believe that, in relinquish- 

 ing the hypothesis of an attractive force between the atoms, 

 we must also relinquish the possibility of any definite con- 

 ception of the influences of the nature of reacting bodies in 

 determining chemical changes. But this is by no means 

 the case. For just as it was formerly supposed that the heat 

 liberated during an act of combination was the equivalent in 

 kinetic energy of so much potential energy due to the attrac- 

 tion of the atoms, it is open to regard the atoms as particles 

 in rapid motion, but devoid of attracting-power, the whole of 

 whose store of energy consists in this motion, and is therefore 

 kinetic; and it may therefore be assumed that such atoms 

 may unite to form molecules, or that such molecules may 

 otherwise react, owing to some as yet undiscovered relation 

 between their modes of motion and velocities. It is of course 

 unnecessary to picture to ourselves attractive forces. They 

 may or may not be conceived, but they are of no great im- 

 portance to science. For my part I believe that a less 

 restricted and prejudiced view of the facts is to be attained 

 by abandoning the hypothesis of mutual attraction between 

 atoms, and avoiding all reference to the unnecessary distinc- 

 tion between the potential and the kinetic energy of the atoms. 



It may fall hard on many who have devoutly believed in 

 the thermal theory of affinity, exalting it high above all facts, 

 to see it dethroned ; perhaps here and there some will refuse 

 to abandon it, like Berzelius with his electrochemical theory, 

 chiefly prompted by the fear that when it is gone the kingdom 

 of chaos, so painfully conquered, may again arise. Yet things 



* " Studien zur chemischen Dynamik," Journ.praht. Chem. xxvii. p. 1 ; 

 xxviii. p. 449; xxix.p. 385; xxxi. p. 307. " Electrochemische Studien," 

 Ibid. xxx. p. 225 ; xxxi. p. 433 ; xxxii. p. 300 j xxxiii. p. 352. 



