Evaluator
Adam Skrzecz Institute of Physical Chemistry, Polish Academy of SciencesEvaluation
A survey of reported compositions along the saturation curve (sat), and compositions of coexisting phases in equilibrium (eq.) for the system 2-propanol-heptane-water is given in Table 64.
Saturation curve
The ternary system 2-propanol-heptane-water forms a large miscibility gap of type 1 covering the majority of the concentration triangle. Only the heptane-water binary system forms a miscibility gap. The data of this binary system were compiled and critically evaluated in a previously published SDS volume.3 The recommended mutual solubilities of the binary system heptane-water at 298.2 are x"2=4.3·10-7 and x'3=5.6·10-4. Solubility of water in heptane x'3=5.5·10-3, reported by Vorobeva and Karapetyants1 is 10 times higher but it is consistent with the accuracy of experiments -0.001 mass fraction. A heptane free point on the saturation curve x1=0.049) in the data of Letcher et al.2 ought to be treated as an artifact of the experimental accuracy. The data are not sufficiently accurate to describe the regions of low concentration of 2-propanol. All compositions of coexisting phases in equilibrium in both data sets are consistent with independently measured saturation curve and with one another. The data of Letcher et al. Ref. 2, show slightly larger solubility for the heptane-poor phase in the region of x2=0.2-0.4. The maximum of 2-propanol concentration is observed on saturation curve which at 298.2 K reaches x1=0.46±0.01 and x2=0.18±0.02 mole fraction. All experimental solubility and equilibrium data reported at 298.2 K were used for calculation of saturation curve. (Water-rich and hydrocarbon-rich branches were treated together.) These data were described by the equation:
x1=0.651 25+0.083 32 ln(x2)-0.261 69x2-0.404 01x22.
The least-squares method was used and the standard error of estimate was 0.0186. The equation describes the saturation curve for <0.91 mole fraction. The compositions on the saturation curve, calculated by the proposed equation are presented in Table 65 for x2 selected concentrations of heptane in the mixture and in Figure 33 as calculated binodal curve (solid line).
Phases in equilibrium
Compositions of coexisting phases in equilibrium for the ternary system 2-propanol-heptane-water were reported in both references at the same temperature 298 K. A plait point of liquid-liquid equilibrium obtained graphically by Vorobeva and Karapetyants1 was x1=0.440 and x2=0.279. The tie lines of Ref. 1 cover the whole range of miscibility gap, while only three tie lines of Ref. 2 cover the middle region of miscibility gap 0.1<x1<0.27. The compositions of phases in equilibrium reported in Refs. 1 and 2 are consistent. The system behavior, calculated saturation curve as well as the experimental data are presented in Figure 33 .
TABLE 65. Calculated compositions along the saturation curve at 298.2
| C $T$ ($\pu{K}$) | D $x_{1}$ | D $x_{2}$ |
|---|---|---|
| 298.2 | 0.0 | 4.3 x 10-7 |
| 298.2 | 7.54 x 10-2 | 1.0 x 10-3 |
| 298.2 | 2.649 x 10-1 | 1.00 x 10-2 |
| 298.2 | 3.199 x 10-1 | 2.00 x 10-2 |
| 298.2 | 3.719 x 10-1 | 4.00 x 10-2 |
| 298.2 | 3.997 x 10-1 | 6.00 x 10-2 |
| 298.2 | 4.173 x 10-1 | 8.00 x 10-2 |
| 298.2 | 4.292 x 10-1 | 1.000 x 10-1 |
| 298.2 | 4.374 x 10-1 | 1.200 x 10-1 |
| 298.2 | 4.429 x 10-1 | 1.400 x 10-1 |
| 298.2 | 4.463 x 10-1 | 1.600 x 10-1 |
| 298.2 | 4.482 x 10-1 | 1.800 x 10-1 |
| 298.2 | 4.487 x 10-1 | 2.000 x 10-1 |
| 298.2 | 4.480 x 10-1 | 2.200 x 10-1 |
| 298.2 | 4.463 x 10-1 | 2.400 x 10-1 |
| 298.2 | 4.437 x 10-1 | 2.600 x 10-1 |
| 298.2 | 4.402 x 10-1 | 2.800 x 10-1 |
| 298.2 | 4.361 x 10-1 | 3.000 x 10-1 |
| 298.2 | 4.312 x 10-1 | 3.200 x 10-1 |
| 298.2 | 4.257 x 10-1 | 3.400 x 10-1 |
| 298.2 | 4.196 x 10-1 | 3.600 x 10-1 |
| 298.2 | 4.128 x 10-1 | 3.800 x 10-1 |
| 298.2 | 4.056 x 10-1 | 4.000 x 10-1 |
| 298.2 | 3.978 x 10-1 | 4.200 x 10-1 |
| 298.2 | 3.895 x 10-1 | 4.400 x 10-1 |
| 298.2 | 3.807 x 10-1 | 4.600 x 10-1 |
| 298.2 | 3.714 x 10-1 | 4.800 x 10-1 |
| 298.2 | 3.616 x 10-1 | 5.000 x 10-1 |
| 298.2 | 3.514 x 10-1 | 5.200 x 10-1 |
| 298.2 | 3.408 x 10-1 | 5.400 x 10-1 |
| 298.2 | 3.297 x 10-1 | 5.600 x 10-1 |
| 298.2 | 3.182 x 10-1 | 5.800 x 10-1 |
| 298.2 | 3.062 x 10-1 | 6.000 x 10-1 |
| 298.2 | 2.939 x 10-1 | 6.200 x 10-1 |
| 298.2 | 2.811 x 10-1 | 6.400 x 10-1 |
| 298.2 | 2.679 x 10-1 | 6.600 x 10-1 |
| 298.2 | 2.544 x 10-1 | 6.800 x 10-1 |
| 298.2 | 2.404 x 10-1 | 7.000 x 10-1 |
| 298.2 | 2.260 x 10-1 | 7.200 x 10-1 |
| 298.2 | 2.113 x 10-1 | 7.400 x 10-1 |
| 298.2 | 1.961 x 10-1 | 7.600 x 10-1 |
| 298.2 | 1.806 x 10-1 | 7.800 x 10-1 |
| 298.2 | 1.647 x 10-1 | 8.000 x 10-1 |
| 298.2 | 1.485 x 10-1 | 8.200 x 10-1 |
| 298.2 | 1.318 x 10-1 | 8.400 x 10-1 |
| 298.2 | 1.148 x 10-1 | 8.600 x 10-1 |
| 298.2 | 9.74 x 10-2 | 8.800 x 10-1 |
| 298.2 | 7.97 x 10-2 | 9.000 x 10-1 |
| 298.2 | 0.0 | 9.9944 x 10-1 |
Figure
Sources:
1
Vorobeva, A. I.; Karapetyants, M. Kh.; Zh. Fiz. Khim. 41, 1984-9 (1967).
2
Letcher, T. M.; Wootton, S.; Shuttleworth, B.; Heyward, C.; J. Chem. Thermodyn 18, 1037 (1986).
3
Shaw, D. G.; 'Hydrocarbons with Water and Seawater, Part I: Hydrocarbons C5 to C7' IUPAC Solubility Data Series, 1989, Vol. 37, Pergamon Press.