TRANSFERENCE OF CHEMICAL AFFINITY. 135 



days, months, or even years, and no action 

 would take place. But by putting them both 

 together and allowing them to touch (fig. 44), 



Fig. 44. 



Fig. 45. 



you see what a coating of copper there is im- 

 mediately thrown down on the platinum. Why 

 is this ? The platinum has no power of itself 

 to reduce that metal from that fluid, but it has 

 in some mysterious way received this power by 

 its contact with the metal zinc. Here then you 

 see a strange transfer of chemical force from one 

 metal to another the chemical force from the 

 zinc is transferred, and made over to the plati- 

 num by the mere association of the two metals. 

 I might take instead of the platinum, a piece 

 of copper or of silver, and it would have no 

 action of its own on this solution, but the mo- 

 ment the zinc was introduced and touched the 

 K 4 



