THEIR CAUSE. 



oxygen has been evolved from the peroxide of that 

 metal. 



A similar phenomenon occurs, when carbonate 

 of silver is treated with several organic acids. Pyr- 

 uvic acid, for example, combines readily with pure 

 oxide of silver, and forms a salt of sparing solubility 

 in water. But when this acid is brought in contact 

 with carbonate of silver, the oxygen of part of the 

 oxide escapes with the carbonic acid, and metallic 

 silver remains in the state of a black powder. 

 (Berzelius.) 



Now no other explanation of these phenomena 

 can be given, than that a body in the act of combina- 

 tion or decomposition enables another body, with 

 which it is in contact, to enter into the same state. 

 It is evident that the active state of the atoms of 

 one body has an influence upon the atoms of a 

 body in contact with it; and if these atoms are 

 capable of the same change as the former, they 

 likewise undergo that change ; and combinations 

 and decompositions are the consequence. But 

 when the atoms of the second body are not capable 

 of such an action, any further disposition to change 

 ceases from the moment at which the atoms of the 

 first body assume the state of rest, that is, when 

 the changes or transformations of this body are 

 quite completed. 



This influence exerted by one compound upon 

 the other, is exactly similar to that which a body 

 in the act of combustion exercises upon a combus- 



Q 



