RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 163 



Hence, the presence of an easily reducible metallic oxide does not seem to 

 increase the oxidizing action of the palladium. 



JExpt. 22. — Several trials were then made in order to ascertain whether by the 

 same general method ethylene could be exhaustively burned. It was found that, 

 using air containing 3,1 per cent, of ethylene, oxidation is only complete (^. e., to 

 COo and H.O) when the palladium asbestos is brought to a temperature of bright 

 redness. At a dull red heat the hydrocarbon may pass partially unburnt. A plat- 

 inum wire spiral (heated by an electric current) was found to be less efficient than 

 palladium asbestos. 



Expt. 23. Absorption of Ethylene hy Palladium. — Pure ethylene (^. e., unmixed 

 with air) was passed over 2 gms. of finely divided palladium contained in a Hempel 

 tube heated to 100. A considerable absorption of the gas occurred, varying in sev- 

 eral trials from | to 5 c.c, according to the duration of the experiment. Unmixed 

 with an excess of air it appears, therefore, that ethylene may undergo an absorption 

 which might cause serious errors in a quantitative gas analysis. With palladium 

 asbestos (6 per cent, palladium) no occlusion of ethylene sufficient to effect the vol- 

 ume of the gas could be observed. 



JExpt. 24. Butlieniam Asbestos. — 



Air 96.9 



EUiylene 3.1 



Oxidation occurred at the following temperatures : 



(1) At 294° (3) At 274° 



(3) " 281° (4) " 320O 



Expt. 25. Osmium Asbestos. — 



Ethylene 3.1 



Air ... 96.9 



Owing to the volatility of osmium in the form of oxide, some difficulty was found 

 in preparing osmium asbestos. Osmic acid was reduced by alcohol and the reduced 

 metal spread upon asbestos. Oxidation occurred at the following temperatures : 



(1) At 150° (5) At 1160 (9) At 160O 



(2) " 140° (6) " 160O (10) " 135° 



(3) " 135° (7) " 170° 



(4) " 120O (8) " 160O 



In the preceding experiments it has been shown that oxidation of the hydro- 

 carbon does not occur each time at the same temperature. The variations are often 

 so great as to preclude the supposition that a cause is to be sought in different con- 



