IUPAC-NIST Solubilities Database

IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Solubility System: Methanol with Hexane (n-hexane) and Water

Components:
   (1) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail
   (2) Hexane (n-hexane); C6H14; [110-54-3]  NIST Chemistry WebBook for detail
   (3) Methanol (methyl alcohol); CH4O; [67-56-1]  NIST Chemistry WebBook for detail

Evaluator:
   A. Skrzecz, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland (1996.04)

Critical Evaluation:

      A survey reported in the literature compositions along the saturation curve (sat.) and compositions of coexisting phases in equilibrium (eq.) for the system methanol-hexane-water is given in Table 8.

Saturation curve The system methanol-hexane-water forms a large miscibility gap of type 2 covering the majority of the concentration triangle. Two binary systems, hexane-water and hexane-methanol, are partially miscible at the reported temperatures. The data for these binary systems were compiled and critically evaluated in previously published SDS volumes, Refs. 5 and 6, respectively. The recommended values⁵ of mutual solubility for the hexane-water system at 293.2 K are: x'₂ = 0.999 47 and x"₂ = 2.5·10^–6. The binary data reported in Ref. 4, x'₂ = 0.999 63 and x"₂ = 3·10^–6, are in very close agreement. The recommended upper critical solution temperature and mutual solubilities at 293.2 K of the methanol-hexane system calculated on the basis of Ref. 6 are: 306.8 K and x'₁ = 0.210, x"₁ = 0.822. These recommended solubilities are exactly the mean value of experimental data reported in the Ref. 3 and Ref. 4 which were also used in evaluation of the binary system. Concentration differences, in mole fraction, in hexane-rich phase are about 0.03 and in hexane-poor phase - 0.006 and 0.02. Measurements along the saturation curve only were reported by Bonner¹ at 273 K and Suhrmann and Walter² in the range 311-323 K. This last paper shows the influence of water on the upper critical solution temperature of the system methanol-hexane. In the other studies phases in equilibrium were presented which may also be treated as points on saturation curve. The data for the hydrocarbon-poor phase on the saturation curve,^3,4 in the region x₃<0.33, were described by the equation:
x₁ = 1.08162 + 0.04830 ln(x₃) – 1.09286x₃. The least-squares method was used and the standard error of estimate was 0.0026. For the selected concentrations of water in the mixture this part of saturation curve was calculated and the results are presented in Table 9 and in Figure 4 as solid line. The part of the saturation curve (hydrocarbon-poor branch) in the region of x₁ 0.65 presents very low concentration of hydrocarbon and on the basis of reported papers the relationship between concentrations of methanol and hexane may be treated as linear. The maximum concentration of methanol in hexane-poor phase of saturation curve, estimated on the basis of Ref. 4, is x₁ = 0.88 and x₂ = 0.08 within an accuracy 0.01 mole fraction. The experimental points of hexane-rich branch of saturation curve contain a very small amount of water and therefore were not described (concentration of water was smaller than 0.0001 mass fraction, Ref. 3).

Phases in equilibrium Compositions of coexisting phases in equilibrium for the ternary system methanol-hexane-water were reported in Refs. 3 and 4 at 283.2 and 293.2 K, respectively. The phases, when equilibrium was reached, were separated and then analyzed in various ways: methanol was determined by reaction with phthalic anhydride, Ref. 3 or by glc, Ref. 4; water was determined by the Karl Fischer reaction.^3,4 The compositions of phases in equilibrium reported in both Refs. 3 and 4 are consistent with one another. They are presented in Figure 4 .

Experimental Data: (Notes on the Nomenclature)

TABLE 8. Summary of experimental data for the system methanol-hexane-water
Author	T/K	DataType	Reference
Bonner, 1909	273	sat. (11)	1
Suhrmann and Walter, 1951	311-323	sat. (7)	2
Kogan et al., 1956	283, 293	Eq. (9)	3
Budantseva et al, 1976	293	Eq. (10)	4

TABLE 9. Calculated compositions along the saturation curve at 293.2 K. (hexane-poor phase)
T/K	Mole Fraction x₁	Mole Fraction x₂	x₃ Note
293.2	0.210	0.0000	Ref. 6
293.2	0.822	0.0000	Ref. 6
293.2	0.8483	0.0100
293.2	0.8708	0.0200
293.2	0.8824	0.0400
293.2	0.8802	0.0600
293.2	0.8722	0.0800
293.2	0.8611	0.1000
293.2	0.8481	0.1200
293.2	0.8337	0.1400
293.2	0.8183	0.1600
293.2	0.8021	0.1800
293.2	0.7853	0.2000
293.2	0.7681	0.2200
293.2	0.7504	0.2400
293.2	0.7324	0.2600
293.2	0.7141	0.2800
293.2	0.6956	0.3000
293.2	0.6769	0.3200
293.2	0.0000	0.999 997 5	Ref. 5
293.2	0.0000	0.000 53	Ref. 5

View Figure 1 for this Evaluation

Notes:
Table 8  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  Suhrmann, R.; Walter, R., Abh. Braunschw. Wiss. Ges. 3, 135 (1951).
   3  Kogan, V.B.; Deizenrot, I.V.; Kulbyaeva, T.A.; Fridman, V.M., Zh. Prikl. Khim (Leningrad) 29, 1387 (1956).
   4  Budantseva, L.S.; Lesteva, T.M.; Nemstov, M.S., Zh. Fiz. Khim. 1976, 50, 1344. Deposited doc. 1976, VINITI 437-76.
   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).
   6  Shaw, D.G.; Skrzecz, A.; Lorimer, J.W.; Maczynski, A., eds., Solubility Data Series, Vol 56, Alcohols with Hydrocarbons (Pergamon, New York, 1994).