1-Proponal with Cyclohexane and Water (IUPAC SDS Volume 69)
Evaluator
Adam Skrzecz Institute of Physical Chemistry, Polish Academy of Sciences
Evaluation
A survey of reported compositions along the saturation curve (sat), and compositions of coexisting phases in equilibrium (eq.) for the system 1-propanol-cyclohexane-water is given in Table 44.

Saturation Curve
The ternary system 1-propanol-cyclohexane-water forms a miscibility gap of type 1 covering the majority of the concentration triangle. Studies of the system were reported in three references at 298.2 K. Only Washburn et al.,1 also investigated this system at 308.2 K. All saturation data are consistent. Only the cyclohexane-water binary system forms a miscibility gap. The data for the binary system were compiled and critically evaluated in a previously published SDS volume;4 the recommended values at 298.2 K are x"2=1.2·10-5 and x'3=3.7·10-4. The end points of the saturation curve, Ref. 2 were reported to be x2=0.998 and pure water which is not consistent with recommended values. However, these results are within the accuracy of experimental measurements (0.005 mole fraction) stated by the authors. One experimental point in the water-rich phases3 was reported to be x1=0.053, x2=0.000, which may suggest that 1-propanol is only partially soluble in water. This numerical result reflects a lack of sensitivity of the analytical method used for cyclohexane in the water-rich phase. All experimental solubility and equilibrium data reported at 298.2 K in Refs. 1,2, and 3, were used to consturct the equation:
x1=a1·(ln z1)a2·z1a23.
where z1=(x2+0.5· x1-x"20)/(x'20-x"20), x1, x2–mole fractions of component (1) and (2), respectively, x'20, x"20-values of x2 on the binodal curve which cuts the x1=0 axis. This equation has been proposed by Letcher et al.5 for the description of saturation curves of the ternary alcohol-ether-water systems. It gives better results (the smallest standard deviation) for the investigated system than any other tested equation. The parameters obtained by the least-squares method for the whole range of miscibility gap (water-rich and hydrocarbon-rich branches were described together) are: a1=1.50825, a2=0.98056, a3=1.28405. The standard error of estimate was 0.0084. For selected concentrations of cyclohexane in the mixture, saturation curve was calculated by the above equation. The results are presented in the Table 45 and in Figure. 22 as solid line.

Phases in equilibrium
  Compositions of coexisting phases in the ternary system 1-propanol-cyclohexane-water at equilibrium were reported in all three references at 298.2 and at 308.2 K (Ref. 1). The tie lines cover the full area of the miscibility gap. The reported equilibrium data sets are not always consistent with one another, although they are consistent within each data set. Inconsistency is observed at the region near the plait point (the water-rich phase in equilibrium with the organic phase containing more than 0.25 mole fraction of alcohol). The data for phases in equilibrium are considered tentative. All experimental tie lines as well as experimental points, Refs. 1, 2, and 3 at 298.2 K are shown in Figure. 22 .
TABLE 45. Calculated composition along the saturation curve at 298.2 K
C $T$ ($\pu{K}$) D $x_{1}$ D $x_{2}$
298.2 0.0 1.2 x 10-5
298.2 2.88 x 10-2 1.0 x 10-3
298.2 1.697 x 10-1 1.00 x 10-2
298.2 2.233 x 10-1 2.00 x 10-2
298.2 2.870 x 10-1 4.00 x 10-2
298.2 3.279 x 10-1 6.00 x 10-2
298.2 3.572 x 10-1 8.00 x 10-2
298.2 3.791 x 10-1 1.000 x 10-1
298.2 3.958 x 10-1 1.200 x 10-1
298.2 4.085 x 10-1 1.400 x 10-1
298.2 4.181 x 10-1 1.600 x 10-1
298.2 4.251 x 10-1 1.800 x 10-1
298.2 4.299 x 10-1 2.000 x 10-1
298.2 4.328 x 10-1 2.200 x 10-1
298.2 4.342 x 10-1 2.400 x 10-1
298.2 4.341 x 10-1 2.600 x 10-1
298.2 4.327 x 10-1 2.800 x 10-1
298.2 4.303 x 10-1 3.000 x 10-1
298.2 4.267 x 10-1 3.200 x 10-1
298.2 4.223 x 10-1 3.400 x 10-1
298.2 4.170 x 10-1 3.600 x 10-1
298.2 4.109 x 10-1 3.800 x 10-1
298.2 4.041 x 10-1 4.000 x 10-1
298.2 3.966 x 10-1 4.200 x 10-1
298.2 3.885 x 10-1 4.400 x 10-1
298.2 3.798 x 10-1 4.600 x 10-1
298.2 3.705 x 10-1 4.800 x 10-1
298.2 3.607 x 10-1 5.000 x 10-1
298.2 3.504 x 10-1 5.200 x 10-1
298.2 3.397 x 10-1 5.400 x 10-1
298.2 3.285 x 10-1 5.600 x 10-1
298.2 3.169 x 10-1 5.800 x 10-1
298.2 3.049 x 10-1 6.000 x 10-1
298.2 2.925 x 10-1 6.200 x 10-1
298.2 2.797 x 10-1 6.400 x 10-1
298.2 2.666 x 10-1 6.600 x 10-1
298.2 2.531 x 10-1 6.800 x 10-1
298.2 2.394 x 10-1 7.000 x 10-1
298.2 2.253 x 10-1 7.200 x 10-1
298.2 2.109 x 10-1 7.400 x 10-1
298.2 1.963 x 10-1 7.600 x 10-1
298.2 1.813 x 10-1 7.800 x 10-1
298.2 1.661 x 10-1 8.000 x 10-1
298.2 1.506 x 10-1 8.200 x 10-1
298.2 1.349 x 10-1 8.400 x 10-1
298.2 1.189 x 10-1 8.600 x 10-1
298.2 1.026 x 10-1 8.800 x 10-1
298.2 8.61 x 10-2 9.000 x 10-1
298.2 6.94 x 10-2 9.200 x 10-1
298.2 5.24 x 10-2 9.400 x 10-1
298.2 3.52 x 10-2 9.600 x 10-1
298.2 1.76 x 10-2 9.800 x 10-1
298.2 8.8 x 10-3 9.900 x 10-1
298.2 0.0 9.9963 x 10-1

Figure
Solubility graph
Sources:

1 Washburn, E. R.; Graham, C. L.; Arnold, G. B.; Transue, L. F.; J. Am. Chem. Soc. 62, 1454 (1940).
2 Letcher, T. M.; Siswana, P.; Radloff, S. E.; S. Afr. J. Chem. 44, 118 (1991).
3 Plackov, D.; Stern, I.; Fluid. Phase Equilib. 71, 189 (1992).
4 Shaw, D. G.; 'Hydrocarbons with Water and Seawater, Part I: Hydrocarbons C5 to C7' IUPAC Solubility Data Series, 1989, Vol. 37, Pergamon Press.
5 Letcher, T. M.; Ravindran, S.; Radloff, S. E.; Fluid Phase Equilib, 69, 251 (1991).