COMPOSITION OF CARBONIC ACID. 29 



there be no strong draft to sweep it away. It may in 

 til is manner be transferred I rem one vessel to another. 



3. A third important property of this eas is, that 

 all animals compelled to breathe it instantly fall, and 

 in a very few moments die. This may be shown by 

 placing a mouse or other small animal in an atmo- 

 sphere of it. Owing to its weight, it sometimes ac- 

 < ' ' > in sheltered hollows, and is the cause of 

 i ulents. In brewers' vats when fermentation 



takt* place, and in some wells, it is apt to collect, and 

 persons lowereil incautiously to clean them suddenly 

 tail insensible. All danger may be avoided by simply 

 lowering a lighted candle before any one goes down: 

 if the camlle burns freely at the bottom, there is no 

 risk in descending. 



This gas consists of carbon and oxygen; 6 lbs. of 

 <M;'>(>n and 16 lbs. of oxygen forming 22 lbs. of car- 

 Ixiiiu; acid. Chemists call it carbon 1 and oxygen 2. 

 It is easy to prove this fact by burning charcoal, which 

 it will be remembered is one form of carbon, in a jar 

 of pure oxygen gas. When the charcoal has ceased 

 to burn, the air remaining in the jar will be carbonic 

 acid; a.s carbon ami nxvir«'n wpre the only two sul^ 

 statu. s pn-srnt, !!>■ "' ■ " ' ". liave 



i»« I n !(i:iiif<l by tl. 



This is another ical 



changes in th»* pi , , i all 



who study this subject soon become familiar. Carbon, 

 a hard inflammable solid, unites with oxygen, a light 

 gas, supporting combastion and animal life in a roost 

 remarkable degree; to form ' ' <. havior 



a much greater weight, ti. If. MM, 



when unmixed with air, destructive to . ■ 



form of life. 



Carbonic acid exists naturally in very large quantity. 

 It is invariably prwent in the .f»".^^>^borc. For a 

 long time this was thought to I tal, but later 



