CARBON DIOXIDE 



57 



the collecting bottle. As the carbon dioxide is a little 

 heavier than the air at the same temperature, it will 

 force the air out of the bottle and will itself stay in as 

 long as the bottle is in an upright position. Can you 

 see, taste, or smell carbon dioxide? Carbon dioxide is 

 not poisonous, but if it is breathed in sufficient quantity 

 it will cause death by keeping oxygen out of the lungs. 

 41. Uses of Carbon Dioxide. Some natural spring 

 waters are charged with carbon dioxide and are called 

 carbonated waters, such as are found at 

 Colorado Springs. Soda water is charged 

 with carbon dioxide. The most valuable 

 commercial use of carbon dioxide is in 

 the fire extinguisher, various forms of 

 which are on the market. The fire extin- 

 guisher used by fire companies and known 

 as the " chemical wagon," and smaller 

 ones for hand use are made of a strong 

 metal case containing a saturated solution 

 of bicarbonate of soda (baking soda) and 

 a glass bottle full of strong sulphuric 

 acid. The bottle is held rigidly in place, PORTABLE FIRE 



but the stopper fits loosely. EXTINGUISHER 



A , ., . . . , . . (Partly Open) 



As long as the extinguisher is in an Showing Stopper . 

 upright position the acid stays in the ed Acid Bottle in 



, c , Original Position. 



bottle and no gas is produced, as the 

 two compounds cannot mix. When the extinguisher is 

 inverted, the acid escapes from the bottle into the soda 

 solution; chemical action then takes place and carbon 

 dioxide gas is set free. The gas produces great pressure 

 in the extinguisher and forces the solution out. This 

 carbonated solution is directed at the base of the fire by 

 a nozzle. Carbon dioxide does not support combustion, 



