Chap. II.] 



LECLANCHE'S ELEMENT. 



work with, owing to absence of fumes. It can, 

 therefore, be allowed on the table at which one is at 

 work. 



Carbon is -f pole, zinc . 



L,eclaiielif's cell (Fig. 12) consists of an outer 

 compartment, containing a zinc 

 cylinder z in a solution of sal- 

 ammoniac. The inner compart- 

 ment is a porous cell T, filled 

 with a mixture of powdered 

 carbon and black oxide of 

 manganese (pyrolusite) sur- 

 rounding a plate of carbon, 

 the mixture being moistened 

 with water, and the whole 

 usually being sealed up. The 

 cell has little force, but remains 

 in good order for a long time, Fig " ^^niT*'' 

 and is specially useful for 



electric bells and telegraphic purposes. Its chemical 

 action is as follows : 



2NH 3 HC1 



Zn 



2 Mn0 2 = ZnCL, + Mn 2 3 -f NH 3 + H 2 0. 



That is, the ammonium chloride attacks the zinc, and 

 the liberated ammonia passing through the porous 

 cell reduces the manganese dioxide to sesquioxide. 

 Small openings in the cover permit of the escape of 

 the unabsorbed ammonia. 



Carbon is -f- pole, zinc . 



CJailFe's cell is a modification of a cell (with 

 the invention of which are associated the names of 

 Marie-Davy, Warren cle la Rue, and Pincus) called 

 the chloride of silver cell. It consists of a plate 

 of zinc z, and a plate of fused chloride of silver 

 Y. They are contained in an ebonite vessel, with a 



