THE METHASK EQLILIBRICM. I1 B Y R. C. CASTELO
It, is quite conceivable that when ethylene is subjected to thermal decomposition, we might have any or all of the reactions indicated below, proceeding either simultaneously or successively. For convenience, the equations have been written in such a way that the left-hand side is a single hydrocarbon. (I) C?HI$2C +zH? C2H1 C*H? H ? (2) ~ ~3 H? ( 3 ) 3 C Z HC6H6 (4) C.‘?HsS2 C 3 H? (j) CzHe -f C2H.j H? (6) C ~ H FC?H? , ~ 2 H? ( 7 ) 3 C * H ? GCaH6 (8) CH, S C 2H2 ( 9 ) 2 CH, S C2H4 2 H? (IO) CH, S C 2H2 etc.
e
+ + + +
+
+ ++
Now it is quite possible to apply the Phase Rule t o such a series of equilibria. .It a sufficiently high temperature, the maximum number of phases is two, the gas and the solid, the variants are fised as temperature and pressure; and the number of components is evidently two. Hence the equation ?;-R+ z = V is satisfied. ( K = n o . of components, R = n o . of phases, and T’=the variants.) The conclusion is reached therefore, that whether the initial system be methane, ethylene, or ethane, the final system must be one in equilibrium. This system may consist of any or all of the substances indicated, but each of these compounds must be present in such a proportion as to preyent a “symphony of equilibria” amongst them all. The question now arises whether it is possible t o predict the quantitative composition of the equilibrium system for a definite temperature and pressure. T o answer this question it is necessary to turn to Thermodynamics for criteria of equilibrium and the simplest is evidently the free energy function. Gibbs’ states that for any isothermal and isobaric process (6
