CARBON 



69 



due to the rushing forth of the confined carbon 

 dioxide. 



If carbon dioxide is poured over a burning candle, 

 the flame is extinguished at once. Carbon dioxide, 

 being heavier than the air, forms a blanket or cover- 

 ing about the candle thereby excluding the air or oxy- 

 gen, and without oxygen fire is impossible. 



This fact gave rise to carbon dioxide fire extin- 

 guishers. These are made of certain chemicals, which 

 when placed together produce 

 carbon dioxide. The chemicals 

 commonly used are bicarbonate 

 of soda and sulphuric acid. The 

 extinguisher consists of a metal- 

 lic case containing a small vessel 

 of strong sulphuric acid em- 

 bedded in the bicarbonate of 

 soda. When the extinguisher is 

 inverted the acid mixes with the 

 soda, producing carbon dioxide 

 which escapes through a tube. 

 As this gas is poured upon a 

 burning object, it forms a layer 

 of the heavier gas about the 

 object, excluding the oxygen 

 and thus extinguishing the 

 fire. 



Fig. 30. Inside view 

 of a fire extinguisher. 



Carbon dioxide also plays an important part in a 

 process which is familiar to all of us, the rising of 



