CH. xxxvi. FARADA VS EXPERIMENTS. 367 



1778, died 1848), discovered several new chemical sub- 

 stances by means of it. 



Faraday's Experiments on the Connection between 

 Electricity and Chemical Affinity. This was the practical 

 use of the discovery; but it had another great interest for 

 chemists, because it proved that electricity can overcome 

 that power called ' chemical affinity/ which holds two or 

 more elements together in one compound substance. You 

 will remember that Bergmann, and indeed Newton before 

 him, pointed out that there is some force which causes 

 certain bodies to choose each other out when they meet, and 

 to unite firmly so as to become a new substance which 

 has its own peculiar characters. Chlorine and sodium, for 

 example, when heated, unite to form common salt, which is 

 not the least like either chlorine or sodium when they are 

 separate ; and in the same way hydrogen and oxygen unite 

 to form water. In these new states they are held together 

 by a power which for want of a better name we call 

 ' chemical attraction/ or 'chemical affinity' (see p. 229). 



Now Davy showed that an electric current conquers 

 this power and sets the different elements free, so that they 

 can each go their own way. Thus the electric current 

 passing through the water overcomes the force which holds 

 the oxygen and hydrogen together, so that, at the point 

 where the battery wires touch the water, hydrogen bubbles 

 come off on one side and oxygen on the other. 



It is to Faraday, however, that we owe most of our 

 knowledge about the intimate connection between electricity 

 and chemical change. He followed up Davy's experiments, 

 and traced out very clearly the cause and effect of the 

 chemical current. He showed in the first place that a sub- 

 stance cannot be decomposed by electricity unless it is a 



