94 GENERAL SCIENCE 



will be at least as much as that furnished by four dry 

 cells, and six or eight cells will be better to hasten the 

 action. It requires much energy to electrolyze water, 

 since the union of the two gases is a strong one. When 

 the batteries are attached, a current will pass through 



the wires and the water, 



oxygen Hydrogen and little bubbles of gas 



will be seen arising from 

 each electrode. The sul- 

 phuric acid furnishes the 

 passageway for the cur- 

 rent between the elec- 



FIG. 91. -An 'Easily Constructed Appa- trodeS. It will be noticed 



that the gas is evolved 



from one electrode much faster than from the other. Test 

 with a glowing splinter the gas in the tube which has the 

 least gas in it. What gas that you have studied does it 

 resemble? Test the gas in the other tube with a flame. 

 This gas is hydrogen, which we shall soon study more 

 fully. The other gas is of course oxygen. What is the 

 approximate proportion of the volumes of the two gases ? 

 Hydrogen is so named because it helps to form water, 

 the Greek word for water being Hydor. Mention some 

 other English words in which this name appears. 



Water by Synthesis. If the gases secured in the pre- 

 ceding experiment are mixed in the same proportion 

 in a tube over mercury and exploded by an electric 

 spark, the result will be water. The proportion of oxygen 

 to hydrogen should be one volume of oxygen to two of 

 hydrogen. Simply mixing these gases, however, will not 

 produce water. The temperature must be high enough 

 (620 C.) to cause action between them. A slight ex- 

 plosion is the evidence of such chemical action. 



