viii THE BURNING OF INFLAMMABLE GASES 159 



It differed from hydrogen in that it burned with a beautiful 

 blue flame, and could not be detonated when mixed with air or 

 oxygen. The same gas was prepared by Priestley in 1783 by 

 heating smithy scale with charcoal 



Fe 3 O 4 + 4C -> 3Fe + 4CO. 



Cruikshank, in 1801, prepared the gas, free from hydrogen, 

 by heating carbonated baryta (barium carbonate), or chalk 

 (calcium carbonate), with iron plates, 



4BaCO 3 + 3Fe -> 4BaO + 4CO + Fe 3 O 4 , 

 4CaCO 3 + 3Fe -> 4CaO + 4CO + Fe 3 O 4 . 



He showed that when exploded with oxygen in Volta's eudio- 

 meter it combined with half its volume of oxygen and gave an 

 equal volume of carbonic anhydride ; he therefore regarded it 

 as a lower oxide of carbon and called it "gaseous oxide of 

 carbon," now carbonic oxide, 



2CO + O 2 -> 2CO 2 



Carbonic oxide Oxygen Carbonic anhydride. 

 i i>oL \ vol. i vol. 



De*sormes and Clement, in 1801, proved by similar experi- 

 ments that Lassone's inflammable gas was an oxide of carbon 

 which gave an equal volume of carbonic anhydride but no water 

 when burnt. They prepared it by the action of charcoal on 

 carbonated baryta, 



BaCO 3 + C-> BaO + 2CO, 



a refractory carbonate which could not be decomposed by heat 

 alone. They could not prepare it by direct combustion of char- 

 coal in air or oxygen, but found that fixed air could be reduced 

 to carbonic oxide bv red-hot charcoal, 



CO 2 + C -> 2CO. 



They also prepared a mixture of carbonic oxide and hydrogen 

 by the action of red-hot charcoal on steam, 



H 2 O + C -> H 2 -j- CO. 



