174 Mr. V. H. Veley on the Phases and 



forces termed chemical affinity and electricity are one and 

 the same/' a sentence which has become the text of the dis- 

 courses of numerous writers in the present generation. With 

 somewhat more reserve Helmholtz * put forward the view 

 that " the very mightiest among chemical forces are of electric 

 origin," which is another frequently quoted text. 



Of course everybody will grant that the chemical changes 

 in a battery and electrolytic cells are identical both in kind 

 and quantity ; everybody also will allow that chemical change 

 and E.M.F. are frequently interdependent variables, and 

 lastly the ionic dissociation theory has a whole school of 

 followers. But it is not as yet possible (notwithstanding a 

 certain array of experimental evidence) in our present state 

 of knowledge to accept Armstrong's definition of chemical 

 change as " reversed electrolysis " f , or the proposition, not 

 wholly identical with it, that in order that chemical change 

 may take place the system operated upon should comprise an 

 electrolyte. For, on the one hand, there are cases of chemical 

 change which do not occur even in the presence of an elec- 

 trolyte, and, on the other, there are cases which occur even 

 in the absence of an electrolyte. 



For example, it will not be denied that dilute hydrochloric, 

 sulphuric, and nitric acids are electrolytes par excellence ; yet 

 for all that certain metals in a state of purity will not dissolve 

 in them. But if, before introduction of the metal, an electric 

 current be passed through these several acids, whereby 

 (possibly) persulphuric, nitrous, and oxygenated chlorine 

 acids are produced, then under these circumstances chemical 

 reaction ensues. Thus electrolysis causes the formation of 

 some intermediate compound ; is it logical, therefore, to con- 

 clude that electrolysis is the necessary antecedent and con- 

 comitant of its own reverse ? 



Again, to take an example from everyday life, the materials 

 of a common match-head and box do not apparently contain 

 an electrolyte, yet the chemical change is violent enough 

 when one is rubbed against the other. At present we are with- 

 out evidence to show that no change would take place if this 

 everyday experiment were performed with absolutely dry 

 materials (especially the potassium chlorate) and in an abso- 

 lutely dry atmosphere. 



It seems most rational to suppose that mechanical is con- 

 verted into heat-energy, which is subsequently degraded by 

 the combustion of the substances present. 



* Journ. Chem. Soc. 1881, p. 277. 



t Proc. Chem. Soc. 1885, p. 40 ; also British Association Report, 1885, 

 p. 953. 



