variation in composition of gas creighton 91 



Variation in the Composition of Compressed Illumin- 

 ating Gas with Pressure as it issues from the Com- 

 pression Cylinder. — By Henry Jermain Maude Creighton, 

 Dr. Sc, F. C. S., Assistant Professor of Chemistry, Swarth- 

 more College, Swarthmore, Penna., U. S. A. 



(Read 9 February. 1920) 



In the course of another investigation it became necessary 

 for the writer to employ an illuminating gas containing 5 to 6 

 per cent, of carbon dioxide. As the content of carbon dioxide 

 in the gas of the laboratory was about one-half this amount, 

 a cylinder of purified carburetted water-gas under a pressure of 

 approximately 300 pounds per square inch was obtained through 

 the courtesy of a neighboring gas company. An analysis of the 

 gas prior to compression gave the following results: 



Per cent. 



Carbon dioxide 5.5 



Illuminants 13_7 



Oxygen 0-9 



Carbon monoxide 26_9 



Hydrogen 35_0\ 



Methane ' I2_4( ^^ n 



Ethane 1 -3^ 



Nitrogen 4.3 



} 



100.0 

 Before employing the gas in the investigation to which refer- 

 ence has been made, the carbon dioxide content in a sample 

 taken from the compression cylinder was determined. To the 

 writer's surprise this amounted to only 3.5 per cent. The same 

 result was obtained with several other samples. On thinking 

 the matter over, the conclusion was reached that the low carbon 

 dioxide content in the samples of gas taken from the compression 

 cylinder must be due to differences in the rates of diffusion of the 

 components of the gas through the very small orifice of the 

 compression cylinder; the heavier carbon dioxide diffusing less 

 rapidly than the lighter hydrogen and methane. In order to 

 substantiate this conclusion, and to ascertain the manner in 

 which the composition of the diffused gas altered with the dif- 

 fusing pressure, analyses were made of samples of gas taken from 

 the compression cylinder as the pressure therein was gradually 

 decreased. 



