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CHAPTER IX 



COMPOUNDS OF CARBON WITH OXYGEN AND NITROGEN 



CARBONIC anhydride (or carbonic acid or carbon dioxide, C0 2 ) was 

 the first of all gases distinguished from atmospheric air. Paracelsus 

 and Van Helmont, in the sixteenth century, knew that on heating 

 limestone a particular gas separated, which is also formed during the 

 alcoholic fermentation of saccharine solutions (for instance, in the 

 manufacture of wine) ; they knew that it was identical with the gas 

 which is produced by the combustion of charcoal, and that in some 

 cases it is found in nature. In course of time it was found that this 

 gas is absorbed by alkali arid saturates it, forming a salt which, under 



In;. <!1. - Dumas and Stas' apparatus for determining the composition of carbonic anhydride. 

 ( 'arbon, uraphite, or a diamond is placed in the tube H in the furnace, and heated in a stream of 

 oxygen displaced from the bottle by water flowing from A. The oxygen is purified from carbonic 

 anhydride and water in the tubes BCD. Carbonic anhydride, together with a certain amount of 

 carbon monoxide, is formed in E. The latter is converted into carbonic acid by passing the pro- 

 duets of combustion through a tube P, containing cupric oxide heated in a furnace. The cupric 

 oxide oxidises this CO into CO.,, forming metallic copper. The potash bulbs H and tubes I, J, 

 K retain the carbonic anhydride. Thus, knowing the weight of carbon taken and the weight of 

 the resultant carbonic anhydride (by weighing H, I, J, K before and after the experiment), the 

 composition of carbonic anhydride and the equivalent of carbon inav be determined. 



the action of acid, again yields this same gas. Priestley found that 

 this gas exists in air, and Lavoisier determined its formation during 

 respiration, combustion, putrefaction, and during the reduction of 

 metals by charcoal ; he determined its composition, and showed that it 

 only contains oxygen and carbon. Berzelius, Dumas with Stas, and 

 Roscoe, determined its composition, showing that it contains twelve 



