The purpose of this post is to come up with reliable data for the vapor-liquid equilibrium (VLE) of solutions made of ethanol (ethyl alcohol $C_2H_5OH$) and water. Notice that in this case, the component of interest is ethanol.
Numerous studies have been published over the past century, but they were disadvantaged by the use of imprecise instruments and poor control of experimental variables. The firsts of these studies are due to William A. Noyes and R. R. Warfel in 1901 [The boiling-point curve for mixtures of ethyl alcohol and water. J. Amer. Chem. Soc. (1901) 23 7] and to P. N. Evans in 1916 [Boiling and condensing points of alcohol water mixtures. J. Ind. Eng. Chem. (1916) 8 3]. In these early studies, the experimental results were reported using the best technology available at the time, which may account for the resulting uncertainty. On the other hand, little discussion of the reliability of these studies appears in subsequent reports. Therefore, these results are not presented here. Fortunately, additional experiments on the ethanol-water mixture were subsequently reported.
Here, data from three sources are presented. These are due to,
- Cornell and Montonna in 1933
- Carey and Lewis in 1932
- Rieder and Thompson in 1949.
The reports by Cornell and Montonna in 1933 and by Carey and Lewis in 1932 seem to be more reliable on the presented data, but neither of them present the boiling temperature due to possible overheating of the mixture. The boiling temperature is an important variable, as it provides a better understanding of the physics and supports the application of the data (e.g., for distillation estimation).
In 1949, Rieder and Thompson published another study on this mixture, using more precise instruments and techniques to show changes in boiling temperature. Also, Rieder and Thompson provide a graphical comparison with all four studies already mentioned, finding that all previous studies results are in very good agreement with their experiments!. Here, the results of Rieder and Thompson are considered the most reliable data.
The first dataset presented was extracted from the paper by L. Wallace Cornell and Ralph E. Montonna in 1933 [Studies in Distillation II. Ind. Eng. Chem. (1933) 25 2].
According to Cornell and Montonna, their experiments were performed at atmospheric pressure ($760\,\, mmHg$). However, in Table II, from which the raw data is taken, they report total pressure oscillations in the range $730-750 \,\,mmHg$. This, of course, can be interpreted as if the total pressure had been monitored but not controlled. The data in their Table II now follows.
| EtOH in liquid (% wt) | EtOH in vapor (% wt) |
|---|---|
| 0.60 | 6.20 |
| 1.10 | 10.90 |
| 2.00 | 20.00 |
| 2.10 | 19.90 |
| 3.00 | 26.20 |
| 3.44 | 29.00 |
| 4.90 | 37.40 |
| 6.15 | 42.30 |
| 6.80 | 44.80 |
| 8.50 | 49.30 |
| 10.14 | 53.10 |
| 13.60 | 58.90 |
| 15.14 | 61.10 |
| 17.14 | 63.00 |
| 19.04 | 64.70 |
| 19.40 | 65.10 |
| 20.90 | 66.30 |
| 22.70 | 67.80 |
| 25.35 | 69.10 |
| 26.85 | 69.70 |
| 29.90 | 71.30 |
| 32.95 | 72.30 |
| 33.30 | 72.90 |
| 36.60 | 73.70 |
| 38.00 | 74.00 |
| 41.24 | 74.80 |
| 45.10 | 75.90 |
| 48.90 | 76.80 |
| 53.00 | 77.60 |
| 57.00 | 78.70 |
| 61.30 | 79.90 |
| 65.60 | 80.90 |
| 68.60 | 81.70 |
| 70.90 | 82.60 |
| 74.80 | 83.90 |
| 78.00 | 85.00 |
| 81.50 | 86.50 |
| 83.90 | 87.70 |
| 86.00 | 88.80 |
| 88.00 | 90.00 |
| 90.10 | 91.30 |
| 92.80 | 93.30 |
| 94.20 | 94.31 |
| 96.28 | 96.16 |
| 98.07 | 97.88 |
The second dataset was reported by J. S. Carey and W. K. Lewis in 1932 [Studies in Distillation. Ind. Eng. Chem. (1932) 24 8]. As you can see, both papers were published with about a year of difference.
Carey and Lewis monitored the total pressure and controlled it to maintain its atmospheric value ($760\,\, mmHg$). Later, in 1933, W. K. Lewis published an errata for one data point (see [Correction - "Studies in Distillation" Ind. Eng. Chem. (1933) 25 12]) which has already been considered.
The raw data presented here were taken from Table I in the 1932 paper of Carey and Lewis. The data in their Table I follows.
| EtOH in liquid (% wt) | EtOH in vapor (% wt) |
|---|---|
| 4.72 | 34.36 |
| 16.57 | 61.95 |
| 21.47 | 66.53 |
| 26.53 | 69.42 |
| 33.74 | 72.59 |
| 43.80 | 75.34 |
| 47.42 | 76.34 |
| 55.43 | 78.11 |
| 62.68 | 80.14 |
| 72.51 | 83.00 |
| 73.45 | 83.22 |
| 77.44 | 84.70 |
| 84.23 | 87.83 |
| 88.31 | 90.14 |
Just for the sake of discussion. Cornell and Montonna state that they compared their results with those of Carey and Lewis and found very good agreement, despite the discrepancy in total pressure. The most difference was found in the mid zone of the data.
The third dataset was reported by Robert M. Rieder and A. Ralph Thompson in 1949 [Vapor-Liquid Equilibria Measured by a Gillespie Still - Ethyl Alcohol - Water System. Ind. Eng. Chem. (1949) 41 12]. This data is considered the most reliable. Again, only the raw data are presented, taken from their Table I. The data in their Table I follows.
| Temperature $^\circ C$ | EtOH in liquid (% wt) | EtOH in vapor (% wt) |
|---|---|---|
| 100.00 | 0.00 | 0.00 |
| 99.30 | 0.71 | 7.72 |
| 96.90 | 2.97 | 24.64 |
| 96.00 | 3.43 | 32.22 |
| 96.00 | 3.61 | 28.56 |
| 95.60 | 4.38 | 32.16 |
| 94.80 | 5.49 | 36.92 |
| 93.80 | 6.07 | 40.73 |
| 93.50 | 7.38 | 43.46 |
| 92.90 | 8.05 | 45.71 |
| 90.50 | 12.29 | 54.42 |
| 90.50 | 12.51 | 53.98 |
| 89.40 | 14.56 | 56.75 |
| 88.40 | 15.58 | 60.06 |
| 88.60 | 16.45 | 59.16 |
| 87.20 | 19.65 | 63.63 |
| 85.40 | 26.85 | 69.19 |
| 84.50 | 29.90 | 70.82 |
| 84.00 | 34.75 | 72.28 |
| 83.40 | 39.85 | 74.23 |
| 83.00 | 40.53 | 73.98 |
| 82.30 | 46.64 | 75.93 |
| 82.00 | 50.29 | 77.00 |
| 81.40 | 54.73 | 78.31 |
| 81.50 | 55.04 | 78.31 |
| 81.20 | 57.40 | 78.72 |
| 80.90 | 63.54 | 80.20 |
| 80.50 | 65.89 | 81.07 |
| 80.20 | 67.58 | 81.51 |
| 80.00 | 72.36 | 83.27 |
| 79.50 | 75.39 | 84.03 |
| 78.80 | 83.39 | 87.55 |
| 78.50 | 87.63 | 89.84 |
| 78.40 | 91.29 | 91.84 |
| 78.30 | 96.58 | 96.10 |
| 78.30 | 100.00 | 100.00 |
Downloadables
If you want to save time, rather than copying/pasting and processing the data to get smoothed data for the mole fraction composition in the liquid and vapor phases, you can download the following Excel file for a small fee. In this document, you will find for each of the above presented studies,
- mole fraction composition in the liquid and vapor phases,
- plots of y vs. x for each dataset,
- plot of y vs. x for smoothed data published by Rieder and Thompson (1949),
- plot of T vs. x,y for smoothed data published by Rieder and Thompson (1949),
- partial and vapor pressures for smoothed data published by Rieder and Thompson (1949),
- relative volatility for smoothed data published by Rieder and Thompson (1949),
- bonus VLE data for mole fractions published in 2001 by K. Iwakabe and H. Kosuge.
This is the end of the post. I hope you find it useful.
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Ildebrando.
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