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 ethanol-2,2,4-trimethylpentane-water is given in Table 37.
Saturation Curve
The system ethanol-2,2,4-trimethylpentane-water forms a miscibility gap of type 1. Experimental points on the saturation curve were reported by Kretschner and Wiebe1 and Nowakowska et al.2 In both references the saturation curves were obtained by the titration method. In Ref. 1 the experimental results at 228, 273, and 298 K were expressed as the water tolerance of the alcohol-hydrocarbon mixture. The binary 2,2,4-trimethylpentane-water system is only partially miscible. The data for this system were compiled and critically evaluated in a previously published SDS volume,4 the binary solubility data were not reported together with ternary data in any of the references. The “best” (Ref.4) values of mutual solubility at 293 and 298 K are x"2=3·10-7, x'2=0.9995 and x"2=3.5·10-7, x'2=0.9994, respectively. Compositions of coexisting phases in equilibrium at 273 and 298 K (Refs. 2 and 3) were included and also used for data comparison on saturation curves. All data sets are consistent with one another. The temperature relationship of miscibility gap, (Refs. 1 and 2) is as expected one. At higher temperatures smaller miscibility gaps are found. The water-rich phase with low concentrations of ethanol (x1<0.20), Ref. 2, was reported to be 2,2,4-trimethylpentane free, presumably due to the analytical methods used. The maximum ethanol concentration is observed on the saturation curve. At 298.2 K it reaches x10.71±0.01 when x20.10±0.02 mole fraction. All experimental solubility and equilibrium data reported at 298.2 K were used for calculation of the saturation curve (Water-rich and hydrocarbon-rich branches were treated together.) These data were described by the equation:
x1=1.021 78+0.104 50 ln(x2)-1.018 38x2.
The parameters were calculated by the least-squares method and the standard error estimate was 0.0243. This equation describes the saturation curve for x2<0.95 mole fraction. The points on the saturation curve, calculated by the above equation together with the “best” values from Ref. 4 are presented in Table 38 for selected concentration of 2,2,4-trimethylpentane in the mixture and in Figure 19 as calculated binodal curve (solid line).
Phases in equilibrium
Compositions of coexisting phases in equilibrium for the ternary system ethanol-2,2,4-trimethylpentane-water were presented in Refs. 2 and 3 and the reported tie lines cover the whole range of the miscibility gap. They were obtained by various analytical methods: refractive indexes, Ref. 2, or by glc, Ref. 3. The direction of tie lines differ slightly. They may be treated as tentative. Experimental tie lines together with all experimental saturation points at 298.2 K are presented in Figure 19 .
TABLE 38. Calculated compositions along the saturation curve at 298.2 K
| C $T$ ($\pu{K}$) | D $x_{1}$ | D $x_{2}$ |
|---|---|---|
| 298.2 | 0.0 | 3.5 x 10-7 |
| 298.2 | 2.989 x 10-1 | 1.0 x 10-3 |
| 298.2 | 5.303 x 10-1 | 1.00 x 10-2 |
| 298.2 | 5.926 x 10-1 | 2.00 x 10-2 |
| 298.2 | 6.447 x 10-1 | 4.00 x 10-2 |
| 298.2 | 6.667 x 10-1 | 6.00 x 10-2 |
| 298.2 | 6.764 x 10-1 | 8.00 x 10-2 |
| 298.2 | 6.793 x 10-1 | 1.000 x 10-1 |
| 298.2 | 6.780 x 10-1 | 1.200 x 10-1 |
| 298.2 | 6.737 x 10-1 | 1.400 x 10-1 |
| 298.2 | 6.673 x 10-1 | 1.600 x 10-1 |
| 298.2 | 6.593 x 10-1 | 1.800 x 10-1 |
| 298.2 | 6.499 x 10-1 | 2.000 x 10-1 |
| 298.2 | 6.395 x 10-1 | 2.200 x 10-1 |
| 298.2 | 6.282 x 10-1 | 2.400 x 10-1 |
| 298.2 | 6.162 x 10-1 | 2.600 x 10-1 |
| 298.2 | 6.036 x 10-1 | 2.800 x 10-1 |
| 298.2 | 5.904 x 10-1 | 3.000 x 10-1 |
| 298.2 | 5.768 x 10-1 | 3.200 x 10-1 |
| 298.2 | 5.628 x 10-1 | 3.400 x 10-1 |
| 298.2 | 5.484 x 10-1 | 3.600 x 10-1 |
| 298.2 | 5.337 x 10-1 | 3.800 x 10-1 |
| 298.2 | 5.187 x 10-1 | 4.000 x 10-1 |
| 298.2 | 5.034 x 10-1 | 4.200 x 10-1 |
| 298.2 | 4.879 x 10-1 | 4.400 x 10-1 |
| 298.2 | 4.722 x 10-1 | 4.600 x 10-1 |
| 298.2 | 4.563 x 10-1 | 4.800 x 10-1 |
| 298.2 | 4.402 x 10-1 | 5.000 x 10-1 |
| 298.2 | 4.239 x 10-1 | 5.200 x 10-1 |
| 298.2 | 4.075 x 10-1 | 5.400 x 10-1 |
| 298.2 | 3.909 x 10-1 | 5.600 x 10-1 |
| 298.2 | 3.742 x 10-1 | 5.800 x 10-1 |
| 298.2 | 3.574 x 10-1 | 6.000 x 10-1 |
| 298.2 | 3.404 x 10-1 | 6.200 x 10-1 |
| 298.2 | 3.234 x 10-1 | 6.400 x 10-1 |
| 298.2 | 3.062 x 10-1 | 6.600 x 10-1 |
| 298.2 | 2.890 x 10-1 | 6.800 x 10-1 |
| 298.2 | 2.716 x 10-1 | 7.000 x 10-1 |
| 298.2 | 2.542 x 10-1 | 7.200 x 10-1 |
| 298.2 | 2.367 x 10-1 | 7.400 x 10-1 |
| 298.2 | 2.191 x 10-1 | 7.600 x 10-1 |
| 298.2 | 2.015 x 10-1 | 7.800 x 10-1 |
| 298.2 | 1.838 x 10-1 | 8.000 x 10-1 |
| 298.2 | 1.660 x 10-1 | 8.200 x 10-1 |
| 298.2 | 1.481 x 10-1 | 8.400 x 10-1 |
| 298.2 | 1.302 x 10-1 | 8.600 x 10-1 |
| 298.2 | 1.122 x 10-1 | 8.800 x 10-1 |
| 298.2 | 9.42 x 10-2 | 9.000 x 10-1 |
| 298.2 | 7.62 x 10-2 | 9.200 x 10-1 |
| 298.2 | 5.80 x 10-2 | 9.400 x 10-1 |
| 298.2 | 5.35 x 10-2 | 9.500 x 10-1 |
| 298.2 | 0.0 | 9.994 x 10-1 |
Figure
Sources:
1
Kretschmer, C. B.; Wiebe, R.; Ind. Eng. Chem. 37, 1130 (1945).
2
Nowakowska, J.; Kretschmer, C. B.; Wiebe, R.; J. Chem. Eng. Data 1, 42 (1956).
3
Huber, J. F. K.; Meijers, C. A. M.; Hulsman, J. A. R.; J. Anal. Chem. 44, 111 (1972).
4
Shaw, D. G.; 'Hydrocarbons with Water and Seawater, Part II: Hydrocarbons C8 to C36' IUPAC Solubility Data Series, 1989, Vol. 38, Pergamon Press.