Common Science 



FIG. 182. Etching copper with acid. 



Drop a little candle grease on a piece of copper about 

 J inch wide and 2 or 3 inches long. In the flame of a Bunsen 

 burner, gently heat the end of the copper that has the candle 

 grease (paraffin) on it, so that the paraffin will spread out 

 all over the end. Let it harden. With a nail, draw a 

 design in the paraffin on the copper, scratching through the 

 thin coat of paraffin to the copper below. Pour a couple of 

 drops of concentrated nitric acid on the paraffin-covered 

 end of the piece of copper, and spread the acid with a match 

 so that it can get down into the scratches. Let it stand by 

 an open window for 5 or 10 minutes. Do not inhale the 

 brown fumes that are given off. They are harmless in small 

 amounts, but if breathed directly they are very irritating. 

 Now wash off the acid by holding the copper under the 

 hydrant, and scrape off the paraffin. 



The nitric acid did to the copper in this experiment 

 exactly what the hydrochloric acid did to the zinc shav- 



