116 



Introduction to the Study of Science 



in diameter and four inches deep; copper wire well insulated and 

 heavily paraffined ; two short pieces of carbon, about the size of a 

 pencil, such as used in an electric arc lamp ; three or four dry cells ; 

 about one ounce of sulfuric acid mixed with about two pints of clean 

 water ; two large test tubes. 



Attach each piece of carbon to one end of the wires, by wrapping 

 tightly, and arrange in the dish about two and one half inches apart 

 (Fig. 35). Holding carbons upright, pour melted paraffin into the 

 dish to a depth of at least half an inch. When the paraffin is hard, 

 cut two or three ditches in the paraffin about one fourth of an inch 

 deep and radiating from the carbons. These should be an inch or 

 two long to provide free exit for water in the tubes. Connect the 



other ends of the wires to the 

 batteries in series. Pour into 

 the dish a solution of water 30 

 parts and sulfuric acid one part 

 to the depth of about two 

 inches. Fill the test tubes with 

 the mixture and invert over 

 the carbons. If the lighting 

 system furnishes direct current 

 of 110 volts, this may be used 

 with a 16 candle power lamp in 

 FIG. 35. Simple apparatus for decom- series to give resistance. This 

 posing water into its elements by dec- curren t will give results more 

 tncity. . . 



quickly. 



The effect of the electric current in the water is soon evident from 

 the small bubbles which, passing from the surface of the carbons to 

 the upper parts of the test tubes, force the water in them downward 

 and out. This process may be continued indefinitely with merely 

 the renewal of the supply of water, the acid remaining undiminished. 

 What conclusion can you draw from this as to the source of the gases ? 



Observe that one tube is filled nearly twice as rapidly as the other. 

 By means of exact and delicate apparatus it can be demonstrated 

 that the gases combine exactly two parts by volume of one to one 

 part of the other in forming water. In your experiment the results 

 showing this may be only approximate because of the partial absorp- 

 tion of the gases by the water ; but they are sufficiently reliable for all 

 practical purposes. 



Remove the tube which is filled first, holding it in the inverted 

 position. Place over the carbon another tube prepared as before 

 described. Into the tube you have taken from the dish, insert a 



