which are evolved in Coal-Mines. 321 



no diminution of the volume, but even an increase of 0.109 

 volume. 



As in this increase of the volume a trace of moisture in the 

 mercury might have had a part, in the second experiment I 

 boiled the mercury in the tube, and proceeded after the cool- 

 ing in the same manner as before. In order to remove the 

 naphtha, the potassium was melted in a narrow glass tube. In 

 this case, likewise, there was an increase of the volume after 

 the heating of the potassium, but it only amounted to 0.036. 

 Two other experiments, with imboiled and boiled mercury, 

 gave the same results. 



Hence it seemed to follow that the pit-gas contained no 

 carbonic oxide gas. Further experiments, which I shall after- 

 wards detail, have however proved, that the potassium cannot 

 be employed for the separation and determination of carbonic 

 oxide gas, when the latter is mixed with carburetted hydro- 

 gen gas. 



The circumstance, that, according to the experiments of M« 

 Despretz,* the oxides of iron, zinc, and tin, are reduced by 

 means of carbonic oxide gas, afforded some, though but little 

 hope, that, perhaps, by employing one of these oxides, a sepa- 

 ration might be effected of this gas from the carburetted hy- 

 drogen gas. As, by experiments which I shall subsequently 

 describe, I obtained the conviction that the inflammable gas 

 from the Welles vveiler pit, is an almost pure carburetted hy- 

 drogen gas, I took* occasion to examine the phenomena pre- 

 sented by it in reference to the above-mentioned oxides. I 

 conducted it very slowly through a tube filled with chloride of 

 calcium, and then through a glass tube which was filled with 

 pure oxide of zinc, and was heated to a bright red heat. This 

 tube was, as in the analysis of organic substances, placed in 

 connection with a tube filled with chloride of calcium, and 

 with the well known apparatus of Liebig, for the absorption 

 of carbonic acid. Some water was in fact produced, whose 

 weight amounted to 3.6 grains, and the solution of potash had 

 absorbed 24.05 grains of carbonic acid. According to this re- 

 sult, the composition of the pit-gas would be as follows : — 



^ Annalci dc Chiaiio ct Uc Physique, t. xliiL p, 222« 



