230 



Our Surroundings 



current, and the silver bar from a rod connected with the positive 

 terminal. As the current passes through the solution, silver is 

 deposited on the spoons. This silver is taken from the solution, 

 where it is replaced by silver dissolved from the silver bar. When 

 the spoons have received the proper thickness of coating, they are 



Storage Battery 



Silver Bar 



on 



ELECTROPLATING A SPOON 



By means of an electric current, silver is taken from the solution and deposited on 

 the spoon. The strength of the solution is sustained by silver drawn from the bar. 



taken out and then rubbed with a smooth iron, called a 'burnisher, 

 to give them luster. Plating with gold or other metals is done 

 in a similar way. 



Electrotyping. Electrotyping is the process of making 

 plates from type for use in printing. The majority of books 

 are now printed from plates. First a mold of a full page 

 of type is made of wax or papier mache. This mold is coated 

 with a thin layer of graphite, a good conductor of electricity. 

 This is necessary because wax and papier mache are poor con- 

 ductors. Then the mold is connected with the negative pole o 

 a battery and immersed in a copper sulphate solution. At 

 the same time a thick plate of copper is connected with the 

 positive pole of the battery and immersed in the solution. 



The current forms a deposit of copper about the thickness 

 of an egg shell all over the mold and makes a copper plate. 

 Then the wax or papier mache is removed. To bear the impact 

 of the printing press without breaking, this copper plate is 



