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-butanol-cyclohexane-water is given in Table 79.
Saturation curve
The ternary system 2-butanol-cyclohexane-water forms a miscibility gap of type 2. Two binary systems, cyclohexane-water and 2-butanol-water, form miscibility gaps. The data for these binary systems were compiled and critically evaluated in previously published SDS volumes, Refs. 3 and 4, respectively. The recommended values of mutual solubility at 298 K are: for cyclohexane-water system x"2=1.2·10-5 and x'3=3.7·10-4, Ref. 3, and for 2 butanol-water systems x'1=0.322 and x"1=0.051, Ref. 4. Letcher et al.2 reported ternary data and mutual solubility for binary systems. The end points of saturation curve were reported to be x'2=0.999 and pure water. This is inconsistent with the recommended values but within the accuracy of experimental measurements (0.001 mole fraction) stated by the authors. Binary solubility data of the 2-butanol-water system reported in Ref. 2 as x'1=0.312 and x"1=0.051 are consistent with the “best values” reported in the critical evaluation, Ref. 3. Plackov and Stern1 reported only solubility of 2-butanol in water, x"1=0.0544. This result is also consistent with recommended data. These experimental data are consistent with one another.
Compositions of the water-rich phase of the ternary system, Refs. 1 and 2, were reported as binary 2-butanol-water mixtures. The analytical methods could not detect cyclohexane. Therefore the water-rich branch could not be evaluated. Phase equilibrium data were used to construct the saturation curve for the organic-rich phase. Data for 298.2 K were described by the equation:
x"1=0.683 11+0.066 20 ln(x2)-0.341 40x2=-0.349 78x22.
The model describes the region 0.01<x2<0.96. The parameters were calculated by the least-squares method. The standard error estimate was 0.0061. The points on the saturation curve calculated by this equation for selected concentrations of cyclohexane in the mixture are presented in Table 80 and in Fig. 43 as a calculated binodal curve (solid line).
Phases in equilibrium
Compositions of coexisting phases in equilibrium for the ternary system 2-butanol-cyclohexane-water were reported in two references at 298.2 K using similar experimental procedures. First equilibrium was reached, then the phases were separated and the composition of each phase was determined. Compositions of water-rich phase in equilibrium were reported as binary 2-butanol-water mixtures; the analytical methods could not detect cyclohexane. The tie lines cover the whole area of the miscibility gap and are consistent within each data set. Distribution of 2-butanol differs between data sets with Letcher et al.2 reporting lower concentrations of alcohol in the water-rich phase than Plackov and Stern.1 Both data sets are treated as tentative. All experimental data points at 298.2 K are reported in Fig. 43 .
Compositions of the water-rich phase of the ternary system, Refs. 1 and 2, were reported as binary 2-butanol-water mixtures. The analytical methods could not detect cyclohexane. Therefore the water-rich branch could not be evaluated. Phase equilibrium data were used to construct the saturation curve for the organic-rich phase. Data for 298.2 K were described by the equation:
TABLE 80. Calculated compositions along the saturation curve at 298.2 K.
| C $T$ ($\pu{K}$) | D $x_{1}$ | D $x_{2}$ |
|---|---|---|
| 298.2 | 3.22 x 10-1 | 0.0 |
| 298.2 | 3.748 x 10-1 | 1.00 x 10-2 |
| 298.2 | 4.172 x 10-1 | 2.00 x 10-2 |
| 298.2 | 4.558 x 10-1 | 4.00 x 10-2 |
| 298.2 | 4.751 x 10-1 | 6.00 x 10-2 |
| 298.2 | 4.863 x 10-1 | 8.00 x 10-2 |
| 298.2 | 4.930 x 10-1 | 1.000 x 10-1 |
| 298.2 | 4.967 x 10-1 | 1.200 x 10-1 |
| 298.2 | 4.983 x 10-1 | 1.400 x 10-1 |
| 298.2 | 4.982 x 10-1 | 1.600 x 10-1 |
| 298.2 | 4.968 x 10-1 | 1.800 x 10-1 |
| 298.2 | 4.943 x 10-1 | 2.000 x 10-1 |
| 298.2 | 4.908 x 10-1 | 2.200 x 10-1 |
| 298.2 | 4.865 x 10-1 | 2.400 x 10-1 |
| 298.2 | 4.815 x 10-1 | 2.600 x 10-1 |
| 298.2 | 4.758 x 10-1 | 2.800 x 10-1 |
| 298.2 | 4.695 x 10-1 | 3.000 x 10-1 |
| 298.2 | 4.626 x 10-1 | 3.200 x 10-1 |
| 298.2 | 4.552 x 10-1 | 3.400 x 10-1 |
| 298.2 | 4.472 x 10-1 | 3.600 x 10-1 |
| 298.2 | 4.388 x 10-1 | 3.800 x 10-1 |
| 298.2 | 4.299 x 10-1 | 4.000 x 10-1 |
| 298.2 | 4.206 x 10-1 | 4.200 x 10-1 |
| 298.2 | 4.108 x 10-1 | 4.400 x 10-1 |
| 298.2 | 4.006 x 10-1 | 4.600 x 10-1 |
| 298.2 | 3.901 x 10-1 | 4.800 x 10-1 |
| 298.2 | 3.791 x 10-1 | 5.000 x 10-1 |
| 298.2 | 3.677 x 10-1 | 5.200 x 10-1 |
| 298.2 | 3.560 x 10-1 | 5.400 x 10-1 |
| 298.2 | 3.438 x 10-1 | 5.600 x 10-1 |
| 298.2 | 3.314 x 10-1 | 5.800 x 10-1 |
| 298.2 | 3.185 x 10-1 | 6.000 x 10-1 |
| 298.2 | 3.053 x 10-1 | 6.200 x 10-1 |
| 298.2 | 2.918 x 10-1 | 6.400 x 10-1 |
| 298.2 | 2.779 x 10-1 | 6.600 x 10-1 |
| 298.2 | 2.637 x 10-1 | 6.800 x 10-1 |
| 298.2 | 2.491 x 10-1 | 7.000 x 10-1 |
| 298.2 | 2.342 x 10-1 | 7.200 x 10-1 |
| 298.2 | 2.190 x 10-1 | 7.400 x 10-1 |
| 298.2 | 2.034 x 10-1 | 7.600 x 10-1 |
| 298.2 | 1.876 x 10-1 | 7.800 x 10-1 |
| 298.2 | 1.714 x 10-1 | 8.000 x 10-1 |
| 298.2 | 1.548 x 10-1 | 8.200 x 10-1 |
| 298.2 | 1.380 x 10-1 | 8.400 x 10-1 |
| 298.2 | 1.208 x 10-1 | 8.600 x 10-1 |
| 298.2 | 1.033 x 10-1 | 8.800 x 10-1 |
| 298.2 | 8.55 x 10-2 | 9.000 x 10-1 |
| 298.2 | 6.74 x 10-2 | 9.200 x 10-1 |
| 298.2 | 4.90 x 10-2 | 9.400 x 10-1 |
| 298.2 | 3.03 x 10-2 | 9.600 x 10-1 |
| 298.2 | 0.0 | 9.9963 x 10-1 |
| 298.2 | 0.0 | 1.2 x 10-5 |
| 298.2 | 5.1 x 10-2 | 0.0 |
Figure
Sources:
1
Plackov, D.; Stern, I.; Fluid. Phase Equilib. 57, 327 (1990).
2
Letcher, T. M.; Siswana, P.; Radloff, S. E.; S. Afr. J. Chem. 44, 118 (1991).
3
Shaw, D. G.; 'Hydrocarbons with Water and Seawater, Part I: Hydrocarbons C5 to C7' IUPAC Solubility Data Series, 1989, Vol. 37, Pergamon Press.
4
Barton, A. F. M.; ed.; Solubility Data Series, Vol. 15, Alcohols with Water (Pergamon, New York 1984).