BATTERIES. 



67 



of manganese, 52 of carbon, 3 of bisulphate of potash, 5 of gum 

 lac rosin acting as a cement to unite the two other substances. 

 This mixture is heated to 100 degrees Centigrade and then 

 submitted to a pressure of 4500 Ib. to the square inch. 



FIG. 6. 



Leclanche Cell. 



The bisulphate of potash facilitates the dissolution of the 

 chloric oxide, which in time penetrates through the pores of 

 the mixture. 



When the circuit is closed, the current decomposes the 

 solution of sal-ammoniac, and a chloric oxide of zinc soluble in 

 the surrounding liquor is formed ; the hydrogen and the 

 ammonia go to the negative electrode, where they effect the 

 reduction of the binoxide of manganese, thereby suppressing 

 all polarisation ; the hydrogen becoming oxidised forms water, 

 and the binoxide is reduced to sesquioxide. When pre- 

 paring the liquid it is necessary to use sal-ammoniac free from 

 metallic salts, and especially of lead, as the latter, depositing 



F 2 



