682 CHEMICAL ACTION IN THE GALVANIC CELL. 



In each element, the current clearly enters the liquid 

 by the zinc plate and leaves it by the copper plate ; con- 

 sequently the zinc plate is the anode and the copper 

 plate the cathode ; the oxygen therefore appears within 

 each cell at the zinc plate, and the hydrogen at the 

 copper plate. It has already been stated that the direc- 



FIG. 346. 



tion of the current within the liquid of the cell is 

 from the zinc to the copper, and a glance at the direc- 

 tion of the arrows in fig. 346 will render the fact still 

 more obvious. 



The oxygen which is thus separated at the zinc plate 

 does not escape in bubbles, for it combines chemically 

 with a portion of the zinc to 'zinc oxide,' which 

 either becomes visible as fine white flakes, as may be 

 seen after using the small battery for some time, 

 fig. 336, or is dissolved in the liquid when acid is 

 present in the water. It is thus that the zinc is ' con- 

 sumed,' as has been mentioned previously. 



The action of the hydrogen which is disengaged at 

 the copper plate, or at the platinum and carbon, if 

 either of these substances is substituted for the copper 

 in a battery arranged as those in fig. 346, or fig. 336, 

 is very different. A part of the hydrogen set free by 



