KESEARCHES UPON THE CTiEMICAL PROPERTIES OF GASES. 173 



chromate of lead, oxide of silvei", permanganate of silver, bichromate of silver. Only 

 a few of the results need be cited here. Silver bichromate heated in ethylene yielded 

 carbon dioxide at the following temperatures : 



(1) At 330° (4) At 250O (8) At 280o 



(2) •' 3790 (5) " 2650 



(3) " 300O (7) " 360O 



In each trial fresh silver bichromate was used. The results are, therefore, similar to 

 those obtained with palladium asbestos. Barely visible traces of carbon dioxide 

 were usually shown by the lime water in advance of the strong reaction which 

 "occurred later. As in the case of oxidation by palladium in air, the hydrocarbon 

 appears to undergo a kind of "smouldering" which changes rather suddenly as the 

 temperature rises to a condition of much more intense oxidation. 



Hempel has suggested that it might be, possible, by a process of selective oxida- 

 tion, to remove consecutively the various constituents of a mixture of combustible 

 gases and in this way establish a method of analysis. The similarity in the proper- 

 ties of the various gases whose oxidation temperatures I have studied, towards air 

 and in presence of metals as well as towards silver bichromate, seems to render 

 doubtful the possibility of such a method. From this statement is to be excepted 

 the determination of hydrogen, the methods for which have been so highly perfected 

 by Hempel and Winkler. 



A. p. s. — VOL. xvn. w. 



