100 Prof. V. B. Lewes. [Fel>. 1. 



products by passing them over heated copper oxide, and estimating 

 the carbon dioxide and water vapour formed. At first the proportion 

 of i ;trbon to hydrogen was 100 to 17*236, which corresponds to 

 m-iirly pure ethylene, and on heating to a higher temperature the 

 ratio altered to 100 carbon to 30'771 hydrogen, which nearly 

 corresponds to methane, carbon being at the same time deposited ; 

 but this is manifestly no proof of the gas being methane, as a mixture 

 of undecornposed ethylene and hydrogen, or mixtures of ethylene, 

 methane, and hydrogen, such as those formed at 1200 C., would give 

 the same result. 



His results were to a certain extent confirmed by Buff and 

 Hofmann, who noticed that when the platinum spiral was heated in 

 pure ethylene there was at once a deposition of carbon, whilst the 

 gas scarcely expands, from which they concluded that methane had 

 been formed at the same time. When, however, the experiments 

 tabulated in Table I are examined, it will be seen that as soon as 

 1200 C. is reached and carbon is deposited expansion takes place ; 

 but that at all temperatures short of that there is contraction due 

 to some of the gaseous products undergoing polymerisation and 

 yielding liquids. In Buff and Hofmann's experiment the gas in 

 contact with the incandescent wire was decomposed with liberation of 

 hydrogen and separation of carbon ; but the expansion caused by 

 this action happened to be nearly equalised by the contraction due to 

 polymerisation in the less heated portions of the gas. 



The simultaneous appearance of carbon and hydrogen indicates 

 clearly the liberation being due to the splitting up of a hydrocarbon, 

 and the proportion in which these elements are liberated point to 

 acetylene as being the body concerned. 



In a paper read before the Chemical Society* I showed that in the 

 interior of a luminous flame the defines are to a great extent con- 

 verted into acetylene, which decomposes at about 1200 C. with 

 liberation of carbon, which, being heated partly by its own combus- 

 tion and partly by the combustion of methane and hydrogen, becomes 

 incandescent, and gives luminosity to the flame, and in the experi- 

 ments which I have described I fully expected to find a higher 

 percentage of acetylene ; but the great tendency towards polymerisa- 

 tion which that body exhibits seems to at once determine its conversion 

 into benzene, which can readily be distinguished among the liquid 

 products, whilst a number of other more complex hydrocarbons are 

 produced, among which crystals of naphthalene are conspicuous. 



In order to ascertain if the behaviour of acetylene when passed 



through the heated tube under the conditions of these experiments 



gave results which support this view, acetylene was prepared by the 



action of dilute hydrochloric acid on acetylide of copper. 



' Chem. Soc. Jour.,' rol. 61, p. 322. 



