A survey of reported compositions along the saturation curve (sat.) and compositions of coexisting phases in equilibrium (eq.) for the system methanol-heptane-water is given in Table 12.

Saturation curve The ternary system methanol-heptane-water forms a very large miscibility gap of type 2 covering the majority of the concentration triangle. The system was studied at five temperatures in the range 273.2-298.2 K. Two binary systems, heptane-water and methanol-heptane form miscibility gap at the reported temperatures. Data for these binaries were compiled and critically evaluated in previously published SDS volumes, Refs. 5 and 6, respectively. In the binary methanol-heptane system the upper critical solution temperature is 324.3±0.2K,⁶. This may be a reason for the large dispersion of solubility reported in the ternary system at temperatures over 300 K. Kogan et al.,² Budantseva et al.,³ and Letcher et al.⁴ also report mutual solubility data for the binary methanol-heptane system; Ref. 3 and Ref. 4 report the same methanol concentration (0.176 mole fraction) at 293 and 298 K respectively. Recommended solubilities of the binaries differ from those reported for the ternary system. The ternary data lack of one component in the phase. This is the result of very low concentrations (<0.001 mole fraction). The ternary solubilities reported in all data sets are consistent with one another. The data are considered tentative. The temperature 293.2 K was selected for presentation of the system behavior. The experimental saturation curve at 293.2 K is presented in Figure 6 . At this temperature the recommended values of mutual solubility are: >x"₂ = 4.3·10^-7, x'₃ = 5.0·10^-4, Ref. 5, for heptane-water system and x"₁ = 0.1364, x'₁ = 0.9037, Ref. 6 for methanol-heptane system. A fitting equation for the saturation curve was not derived because of the law quality of the experimental data. In a few studies the ternary compositions were reported as the binaries, the concentration of the third component was not detectable by the analytical method used. This situation was observed in hydrocarbon-rich phase as well as in hydrocarbon-poor phase.

Phases in equilibrium Compositions of coexisting phases in equilibrium for the ternary system methanol-heptane-water were reported in the temperature range 283-313 K. The tie lines cover the whole area of miscibility gap. The reported equilibrium data sets are consistent with one another. All experimental points at 293.2 K, Refs. 2 and 3, are reported in Figure 6 .