68 ELECTROLYSIS. 



itself in a metallic state in a black spongy mass upon the zinc, 

 would soon destroy it. 



The Leclanche cell is largely used for telegraphic purposes, 

 but it can be used with advantage in electrolytic operations 

 when the baths have a great resistance, as the work is inter- 

 mittent and the number of amperes small. It is possessed of a 

 series of properties which make it quite advantageous in a 

 large number of cases. For instance, the zinc not being 

 attacked by sal-ammoniac, no chemical action takes place when 

 the circuit is open; a cell of dimensions equal to a Daniell 

 has a less resistance than the latter ; it does not contain any 

 poisonous substance ; does not emit any acid vapours or appre- 

 ciable smells ; it resists intense cold without freezing, and 

 consequently without any interruption in its action, &c. 



OXIDE OF COPPER CELL. In the same order of ideas we 

 may mention the oxide of copper cell, the invention of Messrs. 



FIG. 7. 



Oxide of Copper Cell. 



De Lalande and Chaperon (Fig. 7). It is essentially composed 

 of an external vessel V of thin cast iron, having the shape of a 

 large ink-well and constituting the negative electrode, and a 



