160 GENERAL SCIENCE 



flame should be such that only the extreme tips of the outer cone 

 touch the dish. The distance from the burner to the vessel should 

 not be less than 1J inches, as the vessel in contact with the flame 

 will chill it, checking combustion, and wasting gas by only partly 

 burning it. A garlic-like or pungent odor gives warning of such con- 

 ditions. Partly burned gas contains more or less of the poisonous 

 gas carbon monoxide. 



For proper combustion, all fuels must be supplied with many 

 times their weight in air (oxygen). If enough air is not supplied, 

 part of the fuel will not burn; if too much air is supplied, an unneces- 

 sary amount of heat is carried away in the smoke. The economy 

 of different fuels depends upon how completely they burn. It is 

 easy to see that coal is usually not entirely burned, since unburned 

 pieces are found in the ashes. That gas, also, is not always entirely 

 burned is not so well known because unburned gas is not visible. 



On account of the danger of this gas (carbon monoxide) all gas 

 water heaters, and gas and gasoline stoves, as well, should be sup- 

 plied with flues to carry off dangerous or partly burned gases. 



As carbon monoxide has no odor, it is extremely dangerous, 

 for the gas may overcome a person before its presence can be detected. 

 Recovery from such poisoning is less likely than from ordinary gas 

 poisoning, for carbon monoxide unites with the blood, depriving it 

 of oxygen, and seriously affecting the brain. 



QUESTIONS 



1. Why is it necessary to heat the burner of a gasoline stove 

 before lighting the stove? 



2. Why should one avoid cleaning cloth with gasoline in a room 

 where there is a fire? 



3. Why will a match go out without setting kerosene on fire if 

 thrust down into the liquid quickly? 



4. Why do kerosene lamps have wicks? 



5. Why do candles have wicks? 



6. Does the wax of the candle burn? Prove your answer with 

 a match. 



7. Why do some cities forbid the sale of gasoline in open cans 

 after sundown? 



