CHAP, in.] ELECTRICITY AND MAGNETISM. 175 



the current leaves the electrolytic cell. The anions are 

 oxygen, chlorine, etc. When, for example, chloride of 

 tin is electrolysed, metallic tin is deposited on the kath- 

 ode, and chlorine gas is evolved at the anode. 



211. Quantitative Laws of Electrolysis. 



(i.) The amount of chemical action is equal at all points 

 of a circuit. If two or more electrolytic cells are placed 

 at different points of a circuit the amount of chemical 

 action will be the same in all, for the same quantity of 

 electricity flows past every point of the circuit in the 

 same time. If all these cells contain acidulated water, 

 the quantity, for example, of hydrogen set free in each 

 will be the same ; or, if they contain a solution of 

 sulphate of copper, identical quantities of copper will be 

 deposited in each. If some of the cells contain acidu- 

 lated water, and others contain sulphate of copper, the 

 weights of hydrogen and of copper will not be equal, 

 but will be in chemically equivalent quantities. 



(ii.) The amount of an ion liberated at an electrode 

 in a given time is proportional to the strength of the 

 current. A current of 2 webers per second will cause 

 just twice the quantity of chemical decomposition to 

 take place as a current of i weber per second would do 

 in the same time. 



(iii.) The amount of an ion liberated at an electrode 

 in one second is eqital to the strength of the current 

 multiplied by the " electro -chemical equivalent" of the 

 ion. It has been found by experiment that the passage 

 of one weber of electricity through water liberates 

 0000105 gramme 1 of hydrogen. Hence, a current 

 whose strength is C (webers per second) will liberate 

 C x -0000105 grammes of hydrogen per second. The 

 quantity -0000105 is called the electro >- chemical equi- 

 valent of hydrogen. The " electro-chemical equivalents " 

 of other elements can be easily calculated if their 

 chemical " equivalent " is known. Thus the chemical 



1 Kohlrausch says '000010521 ; Mascart says '000010415. 



