CHEMICAL EFFECTS OF THE CURRENT. 673 



Liquid conductors are also heated by the galvanic 

 current. If the circuit of a battery of Bunsen's or 

 Grove's elements is kept closed for a considerable time, 

 the liquids in the cells are sensibly heated, especially 

 when the connecting wires are rather short and thick. 



The most remarkable action of the current upon 

 liquid conductors is their chemical decomposition. All 

 liquids which are chemically compound, and are con- 

 ductors of galvanic electricity, are decomposed by it. 



Chemical decomposition can only be produced with 

 great difficulty by frictional electricity, but very easily 

 by means of the galvanic current, because a continued 

 action is necessary in order that the results of the de- 

 composition may be recognisable. A discussion of these 

 effects of the galvanic current is impossible without enter- 

 ing into -chemical considerations ; a few examples only 

 can therefore find a place here, such cases being chosen 

 as may help the understanding of the chemical action in 

 the elements themselves. 



The chemical decomposition of a substance by the 

 galvanic current is termed c Electrolysis ' (from electro, 

 electric, and lysis, a disengaging); the conductors 

 (wires, plates, or the like), by which the current enters 

 and leaves the substance to be decomposed, are both 

 called ' Electrodes ' (electric ways, from hodos, a way) ; 

 the positive pole by which the current enters the 

 substance is called the ' anode ' (ana, up, and hodos) ; 

 and the negative pole, where it leaves, the ' cathode ' 

 (cata, down, and hodos). 



Sodic sulphate, or Glauber's salt, is one of the sub- 

 stances which may be very easily decomposed. It can be 

 made from sulphuric acid and soda, and the galvanic 



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