242 MEANS OTHER THAN CATALYSIS BY WHICH 



either be similar to that produced by a catalyst, in that it also 

 runs downhill like the reaction inducing it with energy being 

 set free, or may run in the opposite direction away from its 

 equilibrium point, taking up the energy set free in the inducing 

 reaction. 



Even in the first case, where both inducing and induced reac- 

 tion run towards their respective equilibrium points, and energy 

 is set free in both, it is evident that the inducing reaction, other 

 things being equal, will be a more powerful agent in increasing 

 velocity of reaction than a catalyst. For if the catalyst, which 

 can add no energy to the reaction because it remains unchanged 

 itself, can diminish the resistance so as to start or increase the 

 velocity of a reaction, still more can a substance undergoing change 

 and giving out free energy start or hasten a reaction. 



This is not mere theory or hypothesis, but experimental fact, 

 verified by many chemical experiments in everyday laboratory 

 use; the subject seems, however, to be often forgotten or lost sight 

 of from the preponderating attention given to catalytic action. 



No better example can be given than that quoted by Liebig in 

 1840, of the action of nitric acid upon silver in inducing a similar 

 action upon platinum. 



" Platinum, for example, does not decompose nitric acid; 

 it may be boiled with this acid without being oxidised by it, even 

 when in a state of such fine division that it no longer reflects light 

 (black spongy platinum). But an alloy of silver and platinum 

 dissolves with great ease in nitric acid; the oxidation which the 

 silver suffers causes the platinum to undergo the same change; 

 or, in other words, the latter body, from its contact with the 

 oxidising silver, acquires the property of decomposing nitric acid." 



" Electrical action ought to have retarded or prevented the 

 oxidation of the platinum in contact with silver, but, as experience 

 shows, this action is more than counterbalanced by chemical 

 action." 



Examples are also not wanting in inorganic chemistry of where 

 the energy set free in one reaction is used to cause another reaction 

 to proceed away from the direction of its equilibrium point, as 

 in the reduction actions often induced by oxidising agents. For 

 example, in the action of hydrogen peroxide upon certain metallic 

 oxides, such as silver, gold, and peroxide of lead. Here the reaction 

 of formation of water and oxygen from hydrogen peroxide which 



