i8o 



FUELS AND THEIR USES 



terial is almost pure carbon. A little thought must con- 

 vince one that it comes from the candle. If we hold a 



well-dried funnel over the candle 

 flame, we find drops of mois- 

 ture on the inside of the fun- 

 nel. We know the water did 

 not come from the air, because 

 no water settled on the walls 

 of the funnel before the candle 

 was placed under it, therefore 

 we conclude that a burning 

 candle produces water. If we 

 now make some hydrogen gas by 

 pouring a little hydrochloric acid 

 over zinc, and then pass it 

 through a drying chamber as 

 shown in the diagram, we can 

 burn the gas in air. Let us be- 

 fore lighting the gas allow it to 

 pass for two or three minutes 

 into a dry, cold funnel. Watch 

 the inside of the funnel carefully. 

 Does anything happen? Now 

 light the colorless gas and invert 

 the funnel over the flame as 

 before. You will notice that 

 water appears on the inside of the 

 funnel. Since water is formed 



Water is a product of burning hy- 

 drogen. 



both by the burning of the candle and the burning of hydro- 

 gen, it appears that hydrogen is also in the candle. All fuels 

 contain carbon. Most fuels contain carbon and hydrogen 

 as well, and many contain other substances in addition. 



