with iodine or bromine as solutes. Therefore, one must be cautious in using these correlations meant for infinite dilution and be assured that such abnormal behavior as found in methyl alcohol-benzene is not present in the system for which diffusion coefficient is required. We would also like to point out that we have taken viscosity of solvent which is easily available, whereas Wilke and Chang have used viscosity of solution in their equation.The average percentage error remains within 13% for the proposed equation which is the same for Wilke and Chang equation. In the latter case, the diffsuion values for water as solute were not included in calculating the average because the Wilke and Chang equation does not hold good. NOMENCLATURE D = n = v, = M , = x = L, = L = DT = diffusion coefficient, sq. cm./sec. viscosity of solvent in Equation 2 and viscosity of solution molecular volume, cc./gram mole molecular weight of solvent association parameter latent heat of vaporization of solvent, at normal boiling point, cal./gram latent heat of vaporization of solute, at normal boiling point, cal./gram diffusion coefficient calculated by Equation 2in Equation 1, cp.Specific heats of complex saturated hydrocarbons were measured from 100" to 400°F.Major hydrocarbon groups investigated were cyclohexanes, bicyclohexyls, tercyclohexyls, decalins, and hydrindans. A differential heating method employing twin thermal cells was used. The cells were charged with 25 ml. of test fluid and 25 ml. reference fluid (diphenyl ether), respectively, and suspended in air in identical bronze cylinders. These cylinders were, in turn, welded in place to the circular metallic cover of a silicone fluid bath regulated to i~O . 0 2 " F . from 80 to 420°F.The samples were stirred magnetically and the rate of heating of each was followed using Chromel-Alumel thermocouples connected to a precision potentiometer. Calorimetric cell constants were previously obtained with fluids of known specific heats. The over-all accuracy of the method at two temperatures, 104" and 212"F., was determined by measuring fluids of known specific heats. Density and viscosity data obtained by standard techniques are included for each fluid.RECENTLY, greater emphasis has been placed on the physical properties of complex saturated hydrocarbons as potential fuels for supersonic aircraft and advanced missile power plants. In addition t ca density-temperature, viscositytemperature, and vapor pressure-temperature relationships, and heat of combustion, boiling range, freezing point, and thermal stability data, the heat transfer properties of these organics have been examined more closely in the past several years. It is increasingly evident that heat capacity and thermal conductivity information a t higher temperatures is of paramount importance in fully evaluating the potential of any hydrocarbon as a fuel in high performance aircraft and missile vehicles.
