174 EESEAKCHES UPON THE CHEMICAL PROPERTIES OF GASES. 



II. QUALITATIVE EEACTIONS OF GASES. 



The recognition of any gas in a complex mixture is still a matter of difficulty in 

 many cases, although in a few instances methods of identification are coming to be 

 well known. Serious difficulties oppose all attempts at a system of qualitative anal- 

 ysis of gas mixtures. There are but few groups of gases (if the name " group " be 

 understood to include all gases chemically alike); moreover, the members of a group 

 exhibit much closer relationships than are to be found among the metals of any one 

 of the groups of Fresenius. The following classification of gases has been found 

 convenient for purposes of study : 



Group 1. Hydrogen. 



Group 2. Carbon monoxide. 



Group 3. Methane, ethane, propane, the butanes, etc. 



Group 4. Ethylene, propylene, trimethylene, the butylenes, etc. 



Group 5. Acetylene, allylene, etc. 



Group 6. Sulphur compounds : Hydrogen sulphide, methyl hydrosulphide 

 ( (CHy) SH), methyl sulphide ( (CHo)^ S), carbon oxysulphide (COS), carbon bisul- 

 phide. 



Group 7. Carbon dioxide. 



Unclassified : ^tsTitrogen, oxygen. 



In a study of the kind proposed, it is of importance to take into account not 

 only gases that are permanent under ordinary conditions but also vapors of liquids 

 which are liable to occur in small quantities, such as carbon bisulphide, benzol, sev- 

 eral of the lower paraffins and olefines, etc. 



METHODS EMPLOYED. 



In the case of reactions between gases and solid substances, the solid to be tried 

 was placed in a glass tube of one-eighth-inch diameter, which could then be heated 

 to any given temperature in the iron oven previously described, while the gas was 

 caused to stream through the tube. In the case of reactions in solution, two methods 

 were used. 



1. The gas was caused to flow through a capillary tube into the solution con- 

 tained in a test-glass. The escaping gas could then be led into a second and, if 

 necessary, a third test-glass in order to ascertain the action of the solution used in 

 the first test-glass. 



