vin THE BURNING OF INFLAMMABLE GASES 151 



Stas's analysis of carbonic oxide (1849). Eight years 

 later, in 1849, Stas (Works, I. 287-308), carried out a 

 masterly analysis of carbonic oxide, in which 128-367 

 grams of oxygen were used in eight experiments to burn 

 224-683 grams of the gas to 353*050 grams of carbonic 

 anhydride. The experimental methods were very similar 

 to those used by Dumas to determine the composition of 

 water. Thus, instead of using free oxygen to burn the gas, 

 the oxygen was supplied by copper oxide which was reduced 

 to copper by heating it in a current of carbonic oxide. The 

 gas was not weighed directly : its weight was calculated from 

 the difference between the weight of oxygen used and the 

 weight of carbonic anhydride produced. The carbonic 

 anhydride was absorbed and weighed in combination with 

 potash. 



The chief difficulty of the experiment was to provide a 

 supply of carbonic oxide free from carbonic anhydride, 

 oxygen, water, hydrogen and other inflammable gases. The 

 gas was prepared by heating oxalic acid with oil of vitriol : 

 the product, a mixture of carbonic oxide and carbonic 

 anhydride, was passed through potash into a reservoir 

 holding eighty to ninety litres (Fig. 35). From this 

 reservoir the gas was displaced, not by water, but by an 

 alkaline solution capable of absorbing both oxygen and 

 carbonic anhydride. 1 The chief means of removing oxygen, 

 consisted, however, in passing the carbonic oxide through a 

 heated tube containing copper, in which the free oxygen 

 would have every opportunity of being converted into 

 carbonic anhydride. Both before and after passing through 

 this tube the gas was freed from carbonic anhydride and 

 from water by contact with potash and sulphuric acid. The 

 gas prepared in this way contained a little nitrogen but was 

 practically free from all other impurities. 



1 A 5% solution of stannous oxide in potash, made with boiled 

 water, was used. 



