IUPAC-NIST Solubilities Database

IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Solubility System: Methanol with 2,2,4-Trimethylpentane (isooctane) and Water

Components:
   (1) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail
   (2) 2,2,4-Trimethylpentane (isooctane); C8H18; [540-84-1]  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 (1996.05)

Critical Evaluation:

      A survey of reported compositions along the saturation curve (sat.) and compositions of coexisting phases in equilibrium (eq.) for the system methanol-2,2,4-trimethylpentane-water is given in Table 15.

Saturation curve The system methanol-2,2,4-trimethylpentane-water forms a large miscibility gap of type 2 covering the majority of the concentration triangle. Two binary systems 2,2,4-trimethylpentane-water and 2,2,4-trimethylpentane-methanol are partially miscible. The data for these systems were compiled and critically evaluated in previously published SDS volumes, Refs. 3 and 4. The recommended values of mutual solubility of 2,2,4-trimethylpentane-water system, Ref. 3 and methanol-2,2,4-trimethylpentane system, Ref. 4 at 293 K are: x'₂=0.9995, x"₂=3·10^–7 and x'₂=0.890, x"₂=0.224, respectively. (The mutual solubilities of methanol-2,2,4-trimethylpentane system, reported in both papers^1,2 were also considered during evaluation of this binary system in Ref. 4) Compositions along the saturation curve at 291.2 K and 293.2 K by Buchowski and Teperek¹ were obtained by the titration method. They are consistent within each data set, as well as with one another. The paper of Budantseva et al.² contains information about phases in equilibrium at 293.2 K only. The hydrocarbon-poor phase shows smaller miscibility while the hydrocarbon-rich phase shows larger solubility² than data of Ref. 1 at the same temperature and than the “best” binary solubilities by Ref. 4. The data of Buchowski and Teperek,¹ were well documented (description of the method, description of pure substances properties and purity) while data of Ref. 2 were reported without any auxiliary information. Therefore data of Ref. 1 appear reliable, but all are considered as tentative.

Phases in equilibrium Compositions of coexisting phases in equilibrium for the ternary system methanol-2,2,4-trimethylpentane-water were reported in both references. Tie lines cover nearly the whole range of miscibility gap. In the paper of Buchowski and Teperek,¹ the reported hydrocarbon-rich phase did not contain detectable water (water concentration in the hydrocarbon-rich phase was neglected because solubility of water in 2,2,4-trimethylpentane is lower than 0.0005 mass fraction, Ref. 1). The data from Refs. 1 and 2 show slightly different directions of the tie lines. All of them are considered as tentative. To present system behavior, experimental data along the saturation curve and experimental compositions of coexisting phases in equilibrium at 293.2 K, are presented in Fig. 8 .

Experimental Data: (Notes on the Nomenclature)

TABLE 15. Summary of experimental data for the system methanol-2,2,4-trimethylpentane-water
Author	T/K	DataType	Reference
Buchowski and Teperek, 1959	291, 293	sat. (21), eq. (18)	1
Budantseva et al, 1976	293	eq. (6)	2

View Figure 1 for this Evaluation

Notes:
Table 15  Number of experimental points in parentheses.

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

   1  Buchowski, H.; Teperek, J., Rocz. Chem. 33, 1093 (1959).
   2  Budantseva, L.S.; Lesteva, T.M.; Nemstov, M.S., Zh. Fiz. Khim. 1976, 50, 1344. Deposited doc. 1976, VINITI 437-76.
   3  Shaw, D.G., ed., Solubility Data Series, Vol. 37, Hydrocarbons with Water and Seawater, Part I: Hydrocarbons C5 to C7 (Pergamon, New York, 1989).
   4  Shaw, D.G.; Skrzecz, A.; Lorimer, J.W.; Maczynski, A., eds., Solubility Data Series, Vol 56, Alcohols with Hydrocarbons (Pergamon, New York, 1994).