96 Prof. V. B. Lewes. [Feb. 1, 



The two wires are twisted together for a length of 3 mm., and the 

 wires on either side of the twist are then passed through thin glass 

 tabes, which arc fused on to them ; having been in this way coated 

 with glass so that only the twist is exposed, they are passed through 

 the platinum tube, the glass insulating the wire from the tube, and 

 also keeping the thermo-junction in such a position that it registers 

 the temperature of the gas in the tube, not that of the wall of the 

 tube. 



To each end of the platinum tube glass T-pi eces are fitted, down 

 the stems of which the wires pass to mercury seals ; from the metal 

 seals conducting wires lead to the resistance coils, the key, and a 

 reflecting galvanometer. The products, after leaving the platinum 

 tube, pass through a JJ-tnbe, cooled in ice and salt in order to con- 

 dense any liquids, and then through a collecting tube, from which the 

 sample of gas for analysis for gas is taken, thence to Volhard ab- 

 sorption flasks (containing ammoniacal silver nitrate for the estima- 

 tion of acetylene), the flow of the gas through the apparatus being 

 regulated by means of the aspirator bottle. 



In the following set of experiments the ethylene, after purification 

 from oxygen by standing over a dilute solution of sodic pyrogallate 

 and sodic hydrate, \vas passed through the tube at the rate of about 



10 c.c. per minute. 



These experiments are of considerable interest, as they throw 

 some light upon the changes taking place during the heating of 

 ethylene. 



The gas being passed through 140 mm. of heated tube, no change 

 takes place until a temperature of 800 C. is reached, when traces 

 of acetylene are observed ; between 800 and 900 C. the acetylene 

 increases in quantity, and large quantities of methane are gene- 

 rated, accompanied by liquid products. This action increases until 

 just below 1200 C., when hydrogen begins to appear amongst 

 the products of decomposition, -whilst the moment the liberation of 

 hydrogen commences, carbon also is deposited ; and the formation of 



011 decreases until close upon 1500 C., when the decomposition of 

 the ethylene is practically complete, and the products of decompo- 

 sition are mainly hydrogen with some undecomposed methane, and a 

 copious deposit of carbon. 



In each experiment the products of decomposition were examined to 

 see if any member of the C^H^+j group other than methane was 

 present, and in no case could any be detected. This seems to point 

 strongly to the conclusion that the ethane formed in the previous 

 experiment, in accordance with the experiments of Day and Ber- 

 thclot, had its origin as a secondary, and not as a primary, product 

 of decomposition, but it was clear that to determine this point other 

 experiments must be made, to see if under these conditions of tern- 



