160 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



B. COMPOSITION OF THE Two OXIDES OF CARBON. 



Priestley (1772), and Lavoisier (1772), showed that carbon 

 burns in air or oxygen without altering the volume of the 

 gas, 



C + O 2 -> CO 2 

 i vol. i vol. 



This fact was used by Berzelius and Dulong (1820) to 

 determine the composition of carbonic anhydride by comparing 

 its density with that of oxygen. The percentage of carbon 

 (27*65%) agreed with an early determination by Lavoisier (27*9%), 

 but was reduced to 27*27% by the classical experiments of 

 Dumas and Stas (1841), the details of which should be noted 

 carefully. Cruikshank (1801), De*sormes and Clement, and 

 Berthollet measured the changes of volumes produced byexplod- 

 ing carbonic oxide with oxygen ; they found that \ vol. of 

 oxygen was used and gave i vol. of carbonic anhydride. 



CO + ^O 2 -> CO 2 

 I vol. \ vol. i vol. 



Since carbonic anhydride contains an equal volume of oxygen 

 carbonic oxide contains half this volume ; the volume of gas is 

 therefore doubled when carbonic anhydride is reduced by carbon 

 to carbonic oxide, 



CO 2 + C -> 2CO 



I VOl. 2 VOls. 



Stas, in 1849, determined the gravimetric composition of 

 carbonic oxide by passing the gas over weighed copper oxide 

 and weighing the carbonic anhydride produced, 



CO + CuO -> Cu + CO 2 



The precautions taken to prepare a pure gas should be notea. 

 The proportion of carbon was found to be 57'16%. 



C. MARSH GAS AND OLEFIANT GAS. 



Marsh gas (methane, CH 4 ) was discovered by Volta in 

 1776. 



Olefiant gas (ethylene, C 2 H 4 ) was prepared during the alche- 

 mistic period by the action of oil of vitriol on alcohol, 



