The Liquid–Liquid Phase Equilibria of the System Cyclohexane–Methyl Alcohol in the Presence of Various Salts as Third Components.

Abstract

The system cyclohexane-methyl alcohol was first studied by Lecat (8), and the phase data from this investigation are compiled in the International Critical Tables (6). According to these data the critical solution temperature for the system is 49.1°C. In 1926, Mondain-Monval (10) published results on the heat changes produced on mixing cyclohexane and methyl alcohol at various temperatures, from which the phase relationships are deducible. A more careful investigation of this system than had been made previously was undertaken by Jones and Amstell (7), who extended their researches to the effects of added substances on the miscibility temperatures. They studied, as third components, water, acetone, and benzene, and established a method for determining the amount of water in methyl alcohol. According to these workers, the critical solution temperature of the two-component system is 45.60°C. In 1934, Washburn and Spencer ( 16) studied the three-component system cyclohexane-methyl alcoholwater, noting the distribution of methyl alcohol between water and cyclohexane and the freezing-point relationships. The present investigation was undertaken to determine the phase equilibria when various inorganic salts are present. EXPERIMENTAL Purification of cyclohexane Commercial cyclohexane and even better grades are likely to contain impurities due to foreign matter originally present in the benzene together with isomers and products of incomplete hydrogenation. Methylcyclopentane frequently is present and boils only 7°C. below cyclohexane. These two substances are very similar in other respects and their separation is difficult. Seyer, Wright, and Bell (13) have shown that the purification of cyclohexane can best be achieved by efficient rectification, and this method was used in the present work.A fractionating column employing 5-mm. glass helices as packing material was constructed especially to purify cyclohexane. The central tube of the column was 1.9 cm. in diameter and packed for a height of 3.36 meters. Adiabatic 1 This article is based upon a dissertation submitted by E. L. Eckfeldt to the Faculty of the Graduate School of the University of Pennsylvania in partial fulfillment of the requirements for the degree of Doctor of Philosophy, February, 1942. 2 Sincere thanks are due E. I. du Pont de Nemours and Company, Inc., for a Postgraduate Fellowship for the academic year 1940-41.

Multilamellar Structures Induced by Hydrophilic and Hydrophobic Ions Added to a Binary Mixture ofD2Oand 3-Methylpyridine

“…In addition, the same T L was obtained with decreasing and increasing T around the transition. The mass density of D 2 O is 1.11 g/cm 3 and that of 3MP is 0.96 g/cm 3 , so the lighter ordered phase contains more 3MP than the coexisting disordered phase. In this case the mass density difference between the two phases is less than 10 mg/cm 3 .…”

“…However, not enough attention has yet been paid to unique ion effects in such mixtures, where preferential hydration around each ion should affect the composition fluctuations [1,2]. Salts composed of small hydrophilic ions can drastically change the phase behavior even at small concentrations [3,4,5,6,7]. More strikingly, many groups have observed long-lived heterogeneities (sometimes extending over a few micrometers) in one-phase state [8,9] and a third phase visible as a thin plate formed at a liquid-liquid interface in two-phase state [10].…”

“…If φ 3MP is less than the lower bound, the number density of 3MP molecules should be too small to trigger the aggregation of BPh In summary, we have realized the onion structure in a D 2 O-3MP mixture with small 3MP contents by adding a small amount of an antagonistic salt composed of hydrophilic cations and hydrophobic anions. In the previous experiments [3][4][5][6], hydrophilic salts have mostly been used and a number of unsolved controversies have been posed. As demonstrated in this Letter, the effects of adding an antagonistic salt are even more spectacular.…”

Membrane Formation in Liquids by Adding an Antagonistic Salt

“…In particular, the solvation effect on the phase behavior of binary water/organic solvent mixtures is noteworthy. Experiments have established that the two-phase region of a binary mixture tends to expand with the addition of a hydrophilic salt, e.g., NaCl [1][2][3][4]. In such mixtures, both cations and anions preferentially attract water molecules more than the organic solvent molecules, which is a key factor in salt-induced phase separation [3,4].…”

Application of the Theory of Regular Solutions to Binary Phase Equilibria. I. Method of Application to Binary Liquid Equilibria

“…However, in cases of ordinary unsymmetrical systems, values of x do not represent the mole fractions along the consolute curve, but they represent those at the extreme values on the g(x) curve in the neighborhood of the compositions in mutual equilibrium of two phases such as x' and x", which are the two points of contact of the common tangent on the g(x) curve. If the dependency of the logarithms of mole ratio of two components at the compositions in two coexisting phases upon temperature is assumed to be scarcely different from that at the compositions corresponding to the extreme values on the g(x) curve, the following simple relation can be obtained (1,9) for the values of x' and x" on the coexistence curves, where B is a constant independent of temperature.…”