Chemical Change and Energy 295 



FIG. 1 60. The electrodes are made of loops of platinum wire sealed in glass 



tubes. 



which are soldered to two pieces of insulated copper wire, 

 each about 2 feet long. 1 The other ends of the copper wire are 

 bare. Fasten the bare end of one copper wire to one nail 

 of the nail plug if you have direct current (d. c.) in the 

 laboratory, and fasten the bare end of the other wire to the 

 other nail; then turn on the electricity. If you do not 

 have direct current in the laboratory, attach the copper 

 wires to the two poles of a battery instead. 



Bend the platinum electrodes up so that they will stick 

 up into the test tubes from below. Bubbles should im- 

 mediately begin to gather on the platinum wire and to rise 

 in the test tubes. As the test tubes fill with gas, the water 



1 If the copper wire is drawn through a piece of ^-inch soft glass tubing 

 so that only the platinum wire projects from the end of the tube, and the 

 tube is then sealed around the platinum by holding it in a Bunsen burner 

 a few minutes, your electrodes will be more permanent and more satis- 

 factory. The pieces of glass tubing should be about 6 inches long (see 

 Fig. 160). 



