154 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



times and was clearly recognised in van Helmont's work 

 on " gas pingue." But no definite chemical investigation 

 of these gases was made until the composition of water was 

 determined in 1781. It was then proved clearly by the 

 work of Cavendish, of Lavoisier, and of Monge that the gas 

 from metals and acids gave rise to water as the only product 

 of combustion, and in particular that no fixed air was pro- 

 duced. Every other inflammable gas that was examined 

 differed from hydrogen in giving rise to larger or smaller 

 quantities of fixed air. Water was also produced in nearly 

 every case, but Cruikshank in 1801, and De"sormes and 

 Clement in the same year, succeeded in preparing carbonic 

 oxide so far free from hydrogen that no water was produced 

 when it was burned. 



Apart from hydrogen and carbonic oxide, every inflam- 

 mable gas gave both water and fixed air, and was therefore 

 composed of carbon and hydrogen, with or without oxygen. 

 Gases of this kind were prepared by heating wood, charcoal, 

 and oil, by passing spirit of wine through a red hot tube, and 

 so forth. They were examined by Cruikshank, by Berthollet, 

 and by a number of other workers, who determined their 

 relative densities, and their behaviour when exploded with 

 oxygen in Volta's eudiometer, as regards (i) the volume of 

 oxygen used, (2) the contraction after explosion, and (3) the 

 volume of carbonic anhydride produced. But as all the 

 gases examined were mixtures, no concordant results could 

 be obtained. 



Olefiant gas or heavy carburetted hydrogen. The first 

 gaseous compound of carbon and hydrogen to be prepared 

 and examined in a pure state was OLEFIANT GAS. This gas 

 was investigated in 1794 by a group of Dutch chemists 

 (" Researches on the different kinds of gas which are 

 obtained by mixing concentrated sulphuric acid with 

 alcohol," by J. R. Deiman, A. Paets van Troostwyck, 

 N. Bondt and A. Lauwerenburgh, Jour, de Physique, 1794, 



