140 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



and on the contrary, that those which part with it readily, 

 afford the greatest proportion of carbonic acid. 



(3) "That the carbonic acid gas was chiefly disengaged 

 at the beginning of the process, and the purest and greatest 

 quantity of inflammable gas towards the conclusion of it " 

 (loc. tit., p. 3). 



The gas, after washing with lime water to remove the 

 carbonic anhydride, had a density 22/23 of that of a ^ r - 

 When exploded with oxygen in a Volta eudiometer it was 

 converted into fixed air. But it required for its combustion 

 less oxygen than was present in the fixed air produced 

 from it. The gas therefore contained carbon already 

 combined with oxygen, the proportion of carbon being 

 greater and the proportion of oxygen less than in fixed air. 

 Cruikshank described the gas as the GASEOUS OXIDE OF 

 CARBON, but it soon became known as CARBONIC OXIDE. 



Cruikshank prepares carbonic oxide by reducing 

 carbonates with iron, Cruikshank showed that many 

 gallons of the gas could be prepared by heating carbonated 

 baryta or common chalk with iron plates. In this experi- 

 ment fixed air combined with baryta or with lime was 

 reduced to carbonic oxide by the iron, which removed from 

 it a part of the oxygen which it contained. This method 

 of preparation had the advantage of giving a gas which was 

 free from hydrogen ; the gas prepared from charcoal always 

 contained hydrogen, thus affording some justification for 

 Berthollet's view that the gas was a hydrogen-compound. 



Desormes and Clement (1801) investigate the inflam- 

 mable oxide of carbon, The composition of this gas was 

 also investigated in France, by Desormes and Clement. 

 They found, in 1801, that the inflammable gas prepared by 

 heating zinc oxide with charcoal gave no deposit of dew 

 when burnt under a cold bell-jar, and that no drops of water 

 were formed when it was exploded with oxygen over 

 oil. They measured the volume of oxygen used and 



