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Physical and Chemical Examination of three Inflammable Gases 

 which are evolved in Coal-Mines. By Dr Gustav Bischof, 

 Professor of Chemistry in the University of Bonn. Com- 

 municated by the Author. (Concluded from Vol. xxix. 

 p. 333.) 



§ IX. Analysis of Pit-gas in the Detonation-tube. 

 The exact analysis of an inflammable gas in the detonation- 

 tube is, as is well known, somewhat difficult, because only 

 small quantities of gas can be employed. If the analysis be 

 repeated several times, considerable differences take place. 

 The cause of this is principally, that the temperature of the 

 gas is not particularly determined, and that gases, even 

 when standing over mercury, become gradually mixed with 

 atmospheric air. In order as much as possible to remove 

 these two inconveniences, I mixed, in a bottle over water, a 

 quantity of pit-gas sufficient for several experiments, with the 

 requisite quantity of oxygen. I did not fill the bottle entirely 

 with the mixture, but left a very small quantity of water behind. 

 After the bottle had been closed under water by a cork pro- 

 vided with a very narrow long bent (S) tube, it was reversed, 

 and the opening of the tube cut off by mercury. By heating 

 the bottle very slightly, a portion of the gaseous mixture was 

 expelled, which was allowed to enter the detonation-tube filled 

 with mercury, after the first bubbles which contained the at- 

 mospheric air of the tube, together with some drops of water, 

 had been permitted to pass over. As, after the cooling of the 

 bottle, the mercury rose in the narrow tube, the inclosed 

 gaseous mixture remained of itself cut off, and the unchanged 

 position of the metal in the tube was at the same time a sign 

 of the whole being air-tight. In this manner several experi- 

 ments could be performed with the same gaseous mixture, one 

 after another, witbout any admixture of atmospheric air.* 



* I found after wards that the gaseous mixture, when it remains standing 

 in tin- bottl" for scvnil days, becomes gradually mixed with atmospheric air, 

 withoul the mercury sinking in the tube. Thus, on the succeeding days, 

 when the detonations were repeated, there was a constant diminution of 

 the product.-, of the detonation, which could only arise from the atmosphe- 



