VI r.] 



COMPOSITION OF PURE WATER. 



103 



head of water in C will force the gas out of the narrow 

 orifice, and it can be examined as it escapes. On applying 

 a match with its end in a state of glow, it bursts suddenly 

 into flame, and burns vividly (Fig. 26), just as it did in the 

 oxygen described in the last chapter ; we have in fact now 

 obtained oxygen by the decomposition of water. On apply- 

 ing a flame to the gas which issues from the other tube, h, 

 it catches fire and burns with a pale flame ; this is the gas 

 which was formerly known as inflafnmable air, and is now 

 called hydrogen.'^ The longer the current of electricity is 



Fig. 26. — Oxygen and hydrogen from decomposition of water. 



allowed to pass, the more oxygen and hydrogen are 

 generated ; and, if the current could be continued for a 

 sufficient time, all the water might be thus decomposed, 

 and resolved into these two gases. This experiment there- 

 fore shows that pure water consists of oxygen and hydrogen. 

 But it teaches more than this. You cannot fail to observe, 

 from the figures, that the quantity of gas generated is not 

 the same in each tube. In fact, a careful examination 

 shows that twice as much hydrogen as oxygen is obtained. 

 ' Hydrogen, from i/'Scup, hudor, water ; yerj/ocu, gennao, to produce. 



