Chemical Change and Energy 337 



FIG. 177. Cleaning the copper in acids. 



nickel, as shown in Figure 176. Then put the piece of copper 

 in the bottom of an evaporating dish, with the wire hanging 

 out, as in Figure 177. 



Pour over the piece of copper enough of the cleansing 

 solution to cover it. 1 The cleansing solution contains 

 strong acids. If you get any on your skin or clothes, wash 

 it of immediately with ammonia or soda. As soon as the 

 copper is bright and clean, take it out of the cleansing 

 solution and suspend it by the negative wire in the green 

 nickel solution. You can tell if you have it on the 

 negative wire, for in that case bubbles will rise from it 



1 The formula for making the cleansing solution is as follows : 



i cup water. 



i cup concentrated sulfuric acid. 



i cup concentrated nitric acid. 



i teaspoonful concentrated hydrochloric acid. 



The sulfuric and nitric acids must be measured in glass or china cups, 

 and the hydrochloric acid must be measured in a silver-plated spoon 

 or in glass not in tin. 



