EESEAECHES UPON THE CHEMICAL PROPERTIES OF OASES. 161 



about 37° C, was used for the following experiments. It was mainly pentane, as 

 was shown by a vapor density determination, but contained, no doubt, small quanti- 

 ties" of other low-boiling paraffins. Purified air was aspirated through a Woulfe 

 bottle containing a little of the liquid. 



Expt. 17. Palladium Asbestos. — Oxidation occurred : 



(1) At 210° (3) At 180O (5) At 310° 



(3) " 200° (4) " 170O 



7. Heptane. — " Theoline," a commercial product formerly replacing benzol in 

 the San Francisco market, and manufactured by distilling a I'esin from the tree 

 Pinus sahiniana, was shown by Thorpe (^Chem. 8oc. Jour., 1879, p. 296) to consist 

 of normal heptane in an impure state. By digestion with oil of vitriol the paraffin 

 is obtained pure and of constant boiling point (between 98° and 99° C). Heptane 

 was the highest paraffin used in the trials of oxidation temperatures. As this hydro- 

 carbon is readily obtained in a state of purity, and as it was the most complex par- 

 affin employed, it seemed desirable to ascertain whether, on oxidation by palladium 

 asbestos, any unsaturated hydrocarbon resulted. 



Expt. 18. Palladium Asbestos. — Air was aspirated through a Woulfe bottle 

 containing heptane and then through the heated palladium asbestos tube. Oxidation 

 occurred at the following temperatures : 



(1) At 270O (3) At 280° (5) At 300° 



(2) " 270° (4) " 2750 (6) " 290° 



While the experiment was in progress, the air escaping from the palladium 

 asbestos tube was passed through soda solution to absorb the COo formed, and then 

 into palladium chloride solution and finally into lime water. The palladium chloride 

 was reduced to metal and the lime water following it was rendered milky (see reac- 

 tions of CO in solution). This result occurred only when the air was insufficient 

 for complete oxidation of the heptane. With an excess of air, only CO2 and H2O 

 were formed, and no unsaturated hydrocarbon could be detected (olefines and acety- 

 lenes would have caused a reaction in palladium chloride solution ; see reactions of 

 these hydrocarbons in solution). It seems, therefore, that oxidation of the paraffins 

 CH4, C2H6 C7H16 (even when carried on at the lowest possible temper- 

 atures) by excess of air in presence of palladium asbestos yields only CO_> and H2O, 

 although by no means in quantities proportional to the amount of the hydrocarbon 

 originally used. 



OLEFINES. 



8. Ethylene. — This hydrocarbon, on account of the ease with which it is pre- 

 pared and its low temperature of oxidation, is well suited to the study of reactions, 



