1 32 Mr. Pollock on the Action 



acted upon in a similar way. Solution of muriatic acid in 

 water gives off chlorine at the positive and hydrogen at the 

 negative pole. 



By the action of the Voltaic apparatus, the metals of the 

 alkalies and alkaline earths, and boron, may be separated from 

 their combinations with oxygen ; sulphur and carbon, from 

 their combinations with hydrogen. 



The greater the number of the series, the more energetic 

 will be the action of the apparatus. 



By keeping in mind that the pile itself is pervaded by a ra- 

 diant matter which by its motion can produce heat, the cause 

 of its power may be traced out. 



The action going on in each series between the metals and 

 acid or saline solution, should now be considered. 



First, the water is decomposed, by the union of some of the 

 zinc with the oxygen of the water, and hydrogen gas given off 

 from the surface of the copper ; the acid then combines with 

 the oxide of zinc, and remains in solution. 



That portion of the metal, zinc, forming the oxide, by 

 changing the conducting for the non-conducting form, as it 

 exists in the newly formed solution, undergoes an expansion, 

 and an increased capacity for heat ; and the pervading heat 

 which this increase demands will be supplied from that sub- 

 stance with which it is in the most intimate state of contact, 

 which is the remaining metal, zinc : this zinc will in its turn 

 instantly attempt to remunerate itself at the expense of that 

 conducting substance with which it is in contact, which is the 

 copper. The oxide of zinc will unite as soon as formed with 

 the acid in the solution ; there is now a diminution of capacity, 

 a contraction, and the heat thus liberated is seized upon by 

 that body present, which has the greatest capacity for it, which 

 is the hydrogen gas. This gas containing an excess of what 

 the copper is deficient in, they attract each other ; and the 

 equilibrium being restored, the hydrogen gas is given off from 

 the surface of the copper. 



Here, perhaps, it may be considered strange that the hy- 

 drogen, being produced in close contact with the zinc, should 

 be elicited from the surface of the copper in preference to that 

 of the zinc; but the very instant that the zinc suffers a loss of 

 radiant matter, that very instant will this loss be supplied 

 by the copper, as metals are conductors, and the copper re- 

 munerating itself at the expense of those bodies in its vicinity, 

 as the solution, the hydrogen will naturally be attracted by 

 it, and repelled from that part where the saline compound of 

 zinc must be formed, which must be in contact with the zinc. 



Thus, as it appears that in the series of the zinc, copper and 



solution. 



