22 



PHYSIOLOGICAL PHYSICS. 



[Chap. II. 



Bmiseii's element (Fig. 10) is similar to Grove's, 

 the only difference being that a plate of carbon, of the 

 sort deposited in the necks of the retorts during 

 the manufacture of coal gas, is substituted for the 

 platinum in the inner compartment. This makes the 

 element much less expensive. The chemical action is 

 the same. 



Carbon is + pole, zinc . 



Orenet's element is a single-fluid cell. It is 

 also called the bichromate of potash cell. The plates 



and liquid are contained in a 

 wide-mouthed globe-shaped bottle 

 (Fig. 11). Two plates of com- 

 pressed carbon c c reach from 

 the cap to nearly the bottom 

 of the vessel. Between these 

 is a plate of zinc z, half their 

 size, fixed to a rod which slides 

 up and down through the vul- 

 canite stopper. One binding 

 screw in the stopper com- 

 municates with both carbons, 

 and another with the zinc. The 

 solution is made of dilute sulphuric acid, and a 

 saturated solution of bichromate of 

 potash (about 4 oz. of the bichromate to 

 20 oz. of water). The acid of the solu- 

 tion attacks the zinc, and the liberated 

 hydrogen reduces the bichromate to 

 sesquioxide, which is deposited on the 

 zinc. The intensity of the current is 

 thereby diminished. This is remedied 

 by agitation, which separates the de- 

 posit. 



Grenet's element is not remarkably 

 constant, but it is very convenient to Grenet's Cell. 



Fig. 10. Buu&eii's Ele- 

 ment. 



