202 ELEMENTARY GENERAL SCIENCE CHAP. 



a fact which can be at once simply expressed by chemical 

 symbols : 



Terms used in describing Electrolysis. It is customary in 

 speaking of the decompositions effected by the electric current to 

 use certain terms originally adopted by Faraday. The liquid 

 which conducts the electric current, and is itself decomposed, is 

 known as the electrolyte ; the platinum plates in the voltameter 

 described, or, generally speaking, the ends of the wires coming 

 from the poles of the battery, are called electrodes. Names are 

 given to each of these to distinguish them. That by means of 

 which the current enters the electrolyte, or what is the same 

 thing, the electrode in connection with the carbon pole of a 

 Bunsen's battery, or the positive ( + ) pole of any battery, is 

 called the anode. The electrode by means of which the electric 

 current leaves the electrolyte or that in connection with the 

 zinc or negative ( - ) pole of the battery, is called the kathode. 

 The atoms into which the molecules of the electrolyte are 

 decomposed are referred to as ions. Evidently the ions are 



Anode 



FIG. 107. Current passing through Galvanoscope and an Electrolyte. 



invisible during their passage through the electrolyte. Those 

 ions which collect at the anode are spoken of as anions, those 

 collecting at the kathode are called kathions. It will be clear 

 to the reader that the direction in which the kathions move 

 through the liquid is that which we have spoken of as the 

 direction of the current, namely, from the anode to the kathode 

 (Fig. 107). 



