RESEAECHES UPOIST THE CHEMICAL PROPERTIES OF GASES. 105 



actual burning of the gas with flame. Similar results were obtained in trials with 

 palladium asbestos and ruthenium asbestos, and also when methane and ethane were 

 used. 



9. Propylene. — This gas was prepared by the action of potash on propyl 

 iodide (Erlenmeyer, Zeitsclir. f. Chem., 1864, p. 647). 80 gm. of propyl iodide 

 were heated with 50 gm, of potash and 50 gm. of alcohol over the water bath. The 

 following reaction occurs : 



CjH,! + KOH =: KI + H,0 + CgHg. 



The flask containing the potash and alcohol being connected with a reversed 

 condenser and gently warmed, the propyl iodide is slowly added by a tap funnel, and 

 at a temperature of 40° the reaction begins. The gas so produced was washed with 

 water and digested with oil of vitriol (cold), in which it is insoluble, and finally 

 washed by potash solution. Propylene was also prepared from allyl iodide (Glad- 

 stone and Tribe, J. Ch. Soc, 1874, and also ISTiderist, Ami. Ch. Pharm.^ CXCYI, 

 p. 358). 20 c.c. of allyl iodide mixed with three volumes of alcohol were poured 

 over 30 gm. powdered zinc containing 10 gm. of mossy zinc heated in a flask over a 

 water bath. Powdered zinc becomes during the reaction a hard, compact mass. 

 The addition of mossy zinc and constant agitation serve to facilitate the process. 

 The reaction is as follows : 



C3H5I + C2H5OH + Zn = Zn-^*^^2H5 ^ CjHg 



The propylene so prepared was purified as in the preceding method. Careful 

 tests demonstrated the absence of iodine compounds from the product. Beilstein 

 and Wiegand {Ber., 1882, p. 1498) prepare propylene by the action of propyl alcohol 

 upon phosphoric anhydride. In employing this method, 120 gm. P2O5 were placed 

 in a flask provided with a reversed condenser and propyl alcohol gradually added by 

 a tap funnel. The action is at first very violent and requires cooling of the flask; 

 becomes less and less intense, and finally it is found necessary to heat the flask over 

 asbestos. After about 130 c.c. of propyl alcohol had been added the reaction ceased. 

 The method is satisfactory although the yield is small. A method proposed by 

 Klaus and Kerstein {Ber.^ Vol. IX, p. 695), according to w^hich zinc dust is heated 

 with glycerine, was tried, but with unsatisfactory results. The intense frothing of 

 the mixture renders the process uncontrollable. In the various trials, propylene, as 

 prepared by the first three methods just described, was used. That prepared from 

 allyl iodide seemed to be the purest, as judged by the reactions in solution to be 

 detailed later. 



A. p. S. — VOL. XVII. V. 



