IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

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 Solubility System: Ethanol with Heptane and Water

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Components:
   (1) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail
   (2) Ethanol (ethyl alcohol); C2H6O; [64-17-5]  NIST Chemistry WebBook for detail
   (3) Heptane (n-heptane); C7H16; [142-82-5]  NIST Chemistry WebBook for detail

Evaluator:
   A. Skrzecz, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland (1997.03)

Critical Evaluation:

      A survey of reported compositions along the saturation curve (sat), and compositions of coexisting phases in equilibrium (eq.) and distribution of ethanol between phases (distr.) for the system ethanol-heptane-water is given in Table 28.

Saturation curve    The ternary system ethanol-heptane-water forms a large miscibility gap of type 1 covering the majority of the concentration triangle. The system was investigated by four groups over the temperature range 273-303 K; the saturation data are consistent with one another. Only the heptane-water binary system forms a miscibility gap. The data of this system were compiled and critically evaluated in a previously published SDS volume,⁵ the recommended values at 298 K are: x"₂=4.3·10^–7 and x'₃=5.6·10^–4. The data reported by Schweppe and Lorah² at 303 K, and Vorobeva and Karapetyants,³ at 298 K, include solubility of the binary system heptane-water; x"₂=0.0003 and x'₃<0.005, respectively. These values are less precise and do not agree with the recommended data reported in Ref. 5. All experimental solubility and equilibrium data reported at 298 K in Refs. 3 and 4, were described by the equation: x₁=1.1136+0.1319 ln(x₂)–1.2083x₂+0.0932x²₂.    The parameters were calculated by the least-squares method and the standard error of estimate was 0.0087. The selected points on the saturation curve, calculated by the above equation together with the “best” values of Ref. 5 are presented in Table 29 as in Figure 1 as solid line.

Phases in equilibrium    Compositions of coexisting phases in equilibrium for the ternary system ethanol-heptane-water were reported in Refs. 3 and 4 at 298.2 K. The reported equilibrium data sets are not consistent with one another, although they are consistent within each data set. The data for phases in equilibrium differ very much from one another; they are treated as doubtful. Part of experimental tie lines from both discussed references are crossing one another and therefore they are rejected and not reported in Fig. 15 . These tie lines cover the region of high heptane concentration (>0.79 mole fraction) in the heptane-rich phase.
   The plait point at 298.2 K reported in Ref. 3 is x₁=0.517 and x₂=0.409.

Experimental Data:   (Notes on the Nomenclature)

TABLE 28. Summary of experimental data for the system ethanol-heptane-water

Author	T/K	DataType	Reference
Bonner, 1909	273	sat. (9)	1
Schweppe and Lorah, 1954	303	sat. (24), distr. (7)	2
Vorobeva and Karapetyants, 1966	298	sat. (15), eq. (9)	3
Letcher et al., 1986	298	sat. (8), eq. (3)	4

TABLE 29. Calculated compositions along the saturation curve at 298.2 K

T/K	Mole Fraction x1	Mole Fraction x2
298.2	0.0000	0.000 000 43 Ref. 5
298.2	0.5735	0.0200
298.2	0.6408	0.0400
298.2	0.6703	0.0600
298.2	0.6844	0.0800
298.2	0.6900	0.1000
298.2	0.6903	0.1200
298.2	0.6869	0.1400
298.2	0.6809	0.1600
298.2	0.6729	0.1800
298.2	0.6634	0.2000
298.2	0.6526	0.2200
298.2	0.6407	0.2400
298.2	0.6281	0.2600
298.2	0.6147	0.2800
298.2	0.6007	0.3000
298.2	0.5862	0.3200
298.2	0.5713	0.3400
298.2	0.5559	0.3600
298.2	0.5403	0.3800
298.2	0.5243	0.4000
298.2	0.5081	0.4200
298.2	0.4917	0.4400
298.2	0.4751	0.4600
298.2	0.4583	0.4800
298.2	0.4413	0.5000
298.2	0.4242	0.5200
298.2	0.4070	0.5400
298.2	0.3897	0.5600
298.2	0.3723	0.5800
298.2	0.3548	0.6000
298.2	0.3372	0.6200
298.2	0.3196	0.6400
298.2	0.3019	0.6600
298.2	0.2842	0.6800
298.2	0.2664	0.7000
298.2	0.2486	0.7200
298.2	0.2308	0.7400
298.2	0.2129	0.7600
298.2	0.1951	0.7800
298.2	0.1772	0.8000
298.2	0.1593	0.8200
298.2	0.1414	0.8400
298.2	0.1235	0.8600
298.2	0.1056	0.8800
298.2	0.0877	0.9000
298.2	0.0699	0.9200
298.2	0.0520	0.9400
298.2	0.0341	0.9600
298.2	0.0163	0.9800
298.2	0.0000	0.999 44 Ref. 5

View Figure 1 for this Evaluation

Notes:
Table 28  Number of experimental points in parentheses.

References: (Click a link to see its experimental data associated with the reference)

   1  Bonner, W.D., J. Phys. Chem. 14, 738 (1909-1910).
   2  Schweppe, J.L.; Lorah, J.R., Ind. Eng. Chem. 46, 2391 (1954).
   3  Vorobeva, A.I.; Karapetyants, M., Kh., Zh. Fiz. Khim. 40, 3018 (1966).
   4  Letcher, T.M.; Wootton, S.; Shuttleworth, B.; Heyward, C., J. Chem. Thermodyn 18, 1037 (1986).
   5  Shaw, D.G., ed., Solubility Data Series, Vol. 37, Hydrocarbons with Water and Seawater, Part I: Hydrocarbons C5 to C7 (Pergamon, New York, 1989).

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Last updated: February 18, 2015 (Created: August 17, 2007)