which are evolved in Coal-Mines, 317 



According to the first experiment, 163.6 volumes. 



second ... 154.0 

 third ... 153.1 ... 



Mean . . . 153.6 



If this inconsiderable absorption be entirely ascribed to oxy- 

 gen, the latter would amount to only about 0.002 volume. It 

 is evident, however, that this slight absorption proceeds chiefly 

 from the water through which the nitric oxide gas passed. 

 Hence I believe that the pit-gas contains no oxygen, or at 

 least no appreciable quantity. The evolution of this gas must 

 therefore take place without any co-operation of the atmo- 

 spheric air. This likewise followed from the circumstance, that 

 this gas is evolved with a pressure greater than that of the 

 atmospheric air. When agitated for twenty minutes with a 

 solution of sulphuret of potassium, the absorption amounted 

 to 0.058 volume. But it is plain that the solution had ab- 

 sorbed a portion of the pit-gas. Th. de Saussure, at least, 

 had previously remarked, that inflammable gases are absorbed 

 in considerable quantity by sulphuret of potassium. It was on 

 that account that I was obliged to employ the very imperfect 

 agency of nitric oxide gas for determining quantitatively the 

 oxygen. 



§ 2. Examination for carhonic acid gas. 



The pit-gas renders lime-water turbid. The absorption by 

 means of caustic potash amounted to from 0.041 to 0.043 vo- 

 lume. The original quantity of carbonic acid gas, however, 

 must undoubtedly have been much greater, as the gas in its 

 course comes in frequent contact with, and as it is also collected 

 over, water. 



§ 3. Examination for defiant gas. 



This examination was performed by means of chlorine gas, and 

 in a flask composed of black opaque glass, of the kind called hya- 

 lite glass. After the pit-gas had been freed from caibonic acid 

 gas by agitation with liquid potash, it was mixed with chlorine, 

 and, after the mixture of gases had stood for several minutes 

 over the water used for retaining it, the chlorine was again re- 

 moved by agitation with caustic potash. Another portion of chlo- 

 rine was tested as to its containing atmospheric air, by means 



VOL. XXIX. NO. LVIll. OCTOBER 1840. Y 



