xni CHEMICAL CHANGE BY ELECTRIC CURRENT 201 



with acidulated water and inverted over the platinum plates, 

 as shown in the illustration. When the binding screws are 

 connected with the poles of a battery, consisting of two or three 

 Bunsen's cells, bubbles of gas are immediately seen to appear on 

 the platinum plates, and in a few minutes it will be observed 



FIG. 106. Electrolysis of Water. 



that a quantity of gas has collected in each tube. If we allow 

 the electric current to pass round the circuit for 15 or 20 minutes 

 and then measure the volume of the gas which has collected in 

 each tube, it will be found that the tube over the platinum 

 plate which is connected with the zinc pole of the battery con- 

 tains twice as much gas as that over the plate connected with the 

 carbon pole. Moreover, if the bottom of the tube containing 

 the larger amount of gas be covered with the thumb and the 

 tube be lifted out of the liquid, inverted, and a light applied to 

 the gas, it will be found to burn, showing it to be hydrogen 

 (Chap. XVI). Similarly, if a glowing splinter of wood be 

 plunged into the other gas it will be rekindled, showing it to be 

 oxygen. Hence we see that the passage of a sufficiently strong 

 electric current through water causes it to be decomposed into 

 hydrogen and oxygen, and that twice as much hydrogen by 

 volume as oxygen is formed. Or, 



WATER 



is decomposed by the 

 electric current into 



HYDROGEN 

 [2 vols.] 



and 



OXYGEN 

 [1 vol.] 



