153 



OTHER MODES OF FORCE. 



CATALYSIS, or the chemical action induced by the mere pre- 

 sence of a foreign body, embraces a class of facts which must 

 considerably modify many of our notions of chemical action : 

 thus, oxygen and hydrogen, when mixed in a gaseous state, 

 will remain unaltered for an indefinite period ; but the intro- 

 duction to them of a slip of clean platinum will cause more or 

 less rapid combination, without being in itself in any respect 

 altered. On the other hand, oxygenated water, which is a 

 compound of one equivalent of hydrogen plus two of oxygen, 

 will, when under a certain temperature, remain perfectly 

 stable ; but touch it with platinum in a state of minute divi- 

 sion, and it is instantly decomposed, one equivalent of oxygen 

 being set free. Here, again, the platinum is unaltered, and thus 

 we have both synthesis and analysis effected apparently by 

 the mere contact of a foreign body. It is not improbable that 

 the increased electrolytic power of water by the addition of 

 some acids, such as the sulphuric and phosphoric, where the 

 acids themselves are not decomposed, depends upon a catalytic 

 effect of these acids ; but we know too little of the nature and 

 rationale of catalysis to express any confident opinion on its 

 modes of action, and possibly we may comprehend very dif- 

 ferent molecular actions under one and the same name. In no 

 case does catalysis yield us new power or force : it only deter- 

 mines or facilitates the action of chemical force, and, therefore, 

 is no creation of force by contact. 



The force so developed by catalysis may be converted into 

 a voltaic form thus : in a single pair of the gas battery pre- 

 viously alluded to, one portion of a strip of platinum is im- 

 mersed in a tube of oxygen, the other in one of hydrogen, 

 both the gases and the extremities of the platinum being 

 connected by water or other electrolyte ; a voltaic combina- 



