TL EIR CAUSE. 271 



manganese, so that half of the oxygen has been evolved from the 

 peroxide of that metal. 



A similar phenomenon occurs, when carbonate of silver is 

 treated with several organic acids. Pyruvic 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 combination or decomposition ena- 

 bles 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 con- 

 tact with it ; and if these atoms are capable of the same change 

 as the former, they likewise undergo that change ; and combina- 

 tions and decompositions are the consequence. But when the 

 atoms of the second body are not of themselves capable of such 

 an action, any further disposition to change ceases from the 

 moment at which u.e 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 combustible body in its vicinity ; with this dif- 

 ference only, that the causes which determine the commencement 

 and duration of the condition of change are different. For the 

 cause, in the case of the combustible body, is heat, which is 

 generated every moment anew ; whilst in the phenomena of 

 decomposition and combination, which we are considering at pre 

 sent, the cause is a body in the state of chemical action, which 

 exerts the decomposing influence only so long as this action 

 continues. 



Numerous facts show that motion alone exercises a consi- 

 derable influence on chemical forces. Thus, the power of 

 cohesion does not act in many saline solutions, even when 

 they are fully saturated with salts, if they are permitted to 

 cool whilst at rest. In such a case, the salt dissolved in a liquid 



