Potassium ethanol-water system, salt

To illustrate how large the effect of a dissolved salt can be, Figure 2, calculated from the data of Meranda and Furter (I), is included to demonstrate by how much potassium acetate alters the vapor-liquid equilibrium relationship of the system, boiling ethanol-water at atmospheric pressure. The dotted curve represents the ethanol-water system alone, where the azeotrope occurs at about 87 mole % ethanol. The other curves are for various concentrations of potassium acetate, and all are... 

Figure I. Salt effect of potassium iodide on the ethanol-water system at...

Figure 6. Salt effects on the potassium acetate-ethanol-water system at x = 0.245, A and x = 0.311, O...

Figure 2.1a shows an example of a solute that decreases the viscosity of the solvent in this system (Kl-water) a minimum viscosity is exhibited. Several other potassium and ammonium salts also exhibit a similar behaviour. Figure 2.1b shows the effect of concentration and temperature on the ethanol-water system which exhibits a maximum viscosity. 

The salt effects of potassium bromide and a series office symmetrical tetraalkylammonium bromides on vapor-liquid equilibrium at constant pressure in various ethanol-water mixtures were determined. For these systems, the composition of the binary solvent was held constant while the dependence of the equilibrium vapor composition on salt concentration was investigated these studies were done at various fixed compositions of the mixed solvent. Good agreement with the equation of Furter and Johnson was observed for the salts exhibiting either mainly electrostrictive or mainly hydrophobic behavior however, the correlation was unsatisfactory in the case of the one salt (tetraethylammonium bromide) where these two types of solute-solvent interactions were in close competition. The transition from salting out of the ethanol to salting in, observed as the tetraalkylammonium salt series is ascended, was interpreted in terms of the solute-solvent interactions as related to physical properties of the system components, particularly solubilities and surface tensions. 

The data in Tables I-XVI (see Appendix for all tables) show the isobaric vapor-liquid equilibrium results at the boiling point for potassium, ammonium, tetramethylammonium, tetraethylammonium, tetra-n-propylammonium, and tetra-n-butylammonium bromides in various ethanol-water mixtures at fixed liquid composition ratios. The temperature, t, is the boiling temperature for all solutions in these tables. In all cases, the ethanol-water composition was held constant between 0.20 and 0.35 mole fraction ethanol since it is in this range that the most dramatic salt effects on vapor-liquid equilibrium in this particular system should be observed. That is, previous data (12-15,38) have demonstrated that a maximum displacement of the vapor-liquid equilibrium curve by salts frequently occurs in this region. In the results presented here, it should be noted that Equation 1 has been modified to... 

An examination of Figures 1-6 indicates that Equation 1 is valid under conditions of constant x for potassium, ammonium, and tetramethylammonium bromides in ethanol-water mixtures. All three salts show an ability to salt out ethanol from these mixtures (i.e., increase its concentration in the equilibrium vapor) which is verified by their k values shown in Table XVIII. Also, the results for tetra-n-propylammonium bromide and tetra-n-butylammonium bromide in ethanol-water mixtures reveal that Equation 1 can be used to predict the salt effects of these systems however, these two salts demonstrate a propensity to salt in ethanol (i.e., decrease its vapor concentration) in ethanol-water mixtures. On the other hand, Figures 7-9 and the data in Table XVIII reveal that Equation 1 cannot be used to correlate the salt effects of tetraethylammonium bromide in ethanol-water. For this system, a linear dependence of log aja vs. z is observed initially however, a gradual levelling off occurs at higher concentrations. 

Isobaric vapor-liquid equilibrium data at atmospheric pressure are reported for the four systems of the present investigation in Tables I-VI. Salt concentrations are reported as mole fraction salt in the solution, while mixed-solvent compositions are given on a salt-free basis. A single fixed-liquid composition was used for potassium iodide and sodium acetate potassium acetate used three—all chosen from the region of ethanol-water composition where relative volatility is highest. In the... 

Salting-Out Effect Owing to Potassium Chloride. Kobzev (I) maintained, in a study of salts of potassium, sodium, lithium, rubidium, and cesium (all in aqueous solutions), that the solubility of a salt in water was related to its salting-out effect. He found that salts with the solubility from 6.4 to 2.8 g equiv wt per 100 mL of water at 25°C caused stratification in all systems except water-methanol and water-ethanol. Salts with solubilities below 2.82 g equiv wt did not cause salting-out. 

Selective oxidation of methyl groups can be achieved by platinum salts in aqueous solution. Thus, p-toluenesulfonic acid is oxidized to the alcohol and then to the aldehyde by the Pt(II)/Pt(IV) system. Likewise the methyl group of ethanol can be oxidized without affecting the hydroxyl group [208]. Potassium or sodium bromate in the presence of cerium ammonium nitrate in a water/di-oxane (2 3) mixture can oxidize toluene into a 1 1 mixture of benzaldehyde and benzoic acid. Ethylbenzenes yielded acetophenones [209]. 

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