208 GENERAL SCIENCE 



noise and numerous electrical disturbances due to the 

 many uses to which electricity is put in the modern 

 city. 



Chemical Effects Electrolysis. In the chapter on 

 water we used the electric current to separate water into 

 the two gases of which it is composed. In this experi- 

 ment the gas was formed at each terminal, but it was 

 formed at the terminal at which the current left the 

 liquid twice as fast as at the other terminal. The larger 

 volume of gas was hydrogen and the smaller volume 

 oxygen. Solutions of a number of compounds may be 

 decomposed in this way. 



Electroplating. If the current is passed through a 

 solution of copper sulphate instead of a solution of sul- 

 phuric acid, the ac- 

 tion is the same with 

 the exception that the 

 copper is deposited at 

 the negative pole in- 

 stead of hydrogen. 



FIG. 183. An Electroplating Bath. Tf . .-, ... i 



If the positive pole is 



made of copper, it slowly wastes away and is deposited 

 on the other pole. This is the method used in com- 

 mercial electroplating. The positive pole is made of 

 the material with which the other pole is to be plated. 

 In Figure 183 the positive pole (anode) is pure silver, 

 while the negative pole (cathode) is the spoon to be 

 plated. These are both placed in a solution of a silver 

 compound. When the current passes, silver is deposited 

 on the spoon. 



The Dynamo. We learned that, when a bar of iron 

 was put in the magnetic field of a coil carrying a current, 

 the bar was magnetized. The reverse of this is also 



