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THEprediction of thermodynamic properties of mixtures of light hydrocarbon vapors has long been a troublesome problem in the petroleum and associated industries. The ability to calculate the enthalpy of various grades of gasoline, for instance, would be of great value in petroleum processing. With the information available at present, however, such a calculation is not possible. If reasonably precise calculations of this type are to be made possible, fundamental data in this area are needed.

Dividing Equation (A6) by Equation (A7) and then using Equation (A9) to eliminate (dya,/dL)/( dT,/dL) one gets where FF is the average value of r in the film. Thus Equation (A10) can be written I+-There remains the problem of evaluating the first term in Equation (A12). This term is the ratio of the energy absorbed For given values of (x,/xp), m, q, and q' by the chemical reaction within the film Equation (A14) can be solved simulto the wall heat flux, and it is given by taneously with Figure A1 [or Equation (A5) with no heterogeneous reaction] to v -yield the value of E .With this simplification for q = 11 and N L~ = 1, q' = 11. The solution to Equation (A14) for this case is shown in Table Al The foregoing analysis leads to the conclusion that for cases of practical importance the steady state value of ro required to account for the imbalance in heat transfer to the bulk and diffusion of reactants from the bulk is so small that it has a negligible effect upon the results as presented in Figure 1. It is also clear that if ro is not equal to its steady state value at the leading edge of the wall (that is the i d o w boundary condition), it will rapidly approach that steady state value as the gas flows down in the L direction. This basic conclusion is unaltered if the foregoing analysis is repeated for other values of q and for other values of the Lewis number.On the other hand if the heterogeneous reaction is rapid enough to prodnce a large value of ( + -1) while the homogeneous reaction is so slow that it would, in the absence of the heterogeneous reaction, produce a small value of ( + -l ) , then clearly the assumption of chemical equilibrium in the bulk is not justified in general. The available correlations for the be divided into two classes. In the prediction of diffusion coefficients may first class theoretical correlations based = a R. Kanial is at Stamford Laboratories, on the works of Einstein (11), Eyring Binary Liquid Diffusion Coefficients

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gram and Virginia Berry aided in the preparation of the results in a form suitable for publication. W. N. Lacey reviewed the manuscript. NOMENCLATUREIn = natural logarithm = mole fraction methane Ppressure, lb. /sq. inch P = probability of a bubble being formed Pb =a bubble point pressure, lb./sq. inch P9 = supersaturation pressure (P5-P), lb./sq. inch ßtime, sec. 0b = time of strain to first bubble, sec. 0m = mean time corresponding to a given value of supersaturation pressure, sec.