Bcuncc progress. 



No. 18. August, 1895. Vol. III. 



CHEMICAL AFFINITY. 



IN the days of prescientific chemistry the term "chemical 

 affinity" was used to indicate the cause of chemical 

 transformations. It was self-explanatory. Simples united 

 to form compounds because they bore a certain resemblance 

 to each other, and it was known that "like draws to like," 

 so that Becker explicitly put forward the proposition that 

 two bodies capable of combination must contain a common 

 principle. There the matter ended. 



As science advanced it was seen that the primary 

 meaning of chemical affinity had to be given up as an 

 explanation, but the term itself was still retained to denote 

 the cause of chemical phenomena, of whatever nature it 

 might eventually prove to be. Attempts were made to 

 identify this cause with one of the known natural forces. 

 Newton and Berthollet, for example, were of opinion that 

 chemical force was a manifestation of gravitational attrac- 

 tion. That it was a form of electrical attraction found 

 supporters in Berzelius, Davy, Grotthus and Gmelin. 

 Williamson attempted to reduce chemical action, as well as 

 the phenomena of heat, light and electricity, to the per- 

 petual movements of the ultimate particles of matter. 



Finally, many chemists were content to describe chemical 



affinity as a "special force" not further characterised. 



Although this position amounts to giving up the problem 



for the meantime, it is that which so far corresponds best 



with our knowledge, or want of knowledge. At present 



30 



