CHAPTER XVIII 

 CHEMICAL EFFECTS OF ELECTRIC CURRENTS 



225. Questions for Discussion. 1. How are knives and spoons plated 

 with silver? 2. Why are articles plated with nickel? 3. How are electro- 

 types made? 4. What materials are needed to plate a piece of steel 

 with copper? 5. How is an automobile storage battery made? 6. What 

 rules should be observed in the use of a storage battery ? 7. How does 

 a battery hydrometer tell the charged or uncharged condition of the 

 battery? 8. How much current must the battery be able to supply iu 

 order to start the gas engine? 9. What is the difference between an 

 Edison storage cell and a lead storage cell? 10. What gases are set 

 free when a storage battery is charged? 11. What is the cost of an 

 automobile storage battery? How long will the battery last? 



226. How to plate articles with copper. Sometimes when 

 one is buying kitchen utensils, table silver, or other metal 

 goods, the dealer says, " This piece is plated, but this piece 

 is solid." For some uses solid ware is preferable, while for 

 other uses plated ware is equally good or better. What is 

 meant by the statement that metal wares are plated, and 

 how is this plating done ? 



In figure 108 an apparatus for copperplating is shown. 

 A piece of clean carbon from an ordinary dry cell is a con- 

 venient article to plate. This is suspended in a solution of 

 copper sulphate from a metal rod connected to the zinc of 

 the battery. The carbon of the battery is connected to a strip 

 of copper. If we permit the current to flow several minutes, 

 a bright coat of copper appears on the carbon. As the cur- 

 rent continues to flow the copper gets thicker on the carbon, 

 and the copper plate grows thinner. Then another interest- 

 ing fact about the chemical effects of electricity appears; 



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