Mole Fraction Of Alcohol Research Articles

Solute-solvent interactions in water-tert-butyl alcohol mixtures. VI. Enthalpies of solution for halo-para-substituted benzoates

Enthalpies of solution of sodium benzoate, potassium benzoate, and potassium halo-substituted benzoates are reported at 298.15°K in water and in nine water-tert-butyl alchol mixtures. Transfer enthalpies from water to the mixed solvent go through a maximum for about 0.055 mole fraction of alcohol. Additivity of ionic contributions in the enthalpies of transfer is verified. Substituent effects on the transfer enthalpies of benzoates are discussed in terms of size of the solutes and cohesion of the solvent mixtures.

Ionic solvation in water + co-solvent mixtures. Part 4.—Free energies of transfer of single ions from water into water + t-butyl alcohol mixtures

The method used to calculate the free energy of transfer of the proton, ΔG°t(H+), from water into mixtures of water with various co-solvents has now been applied to water + t-butyl alcohol mixtures: the extra-thermodynamic assumptions involved in these calculations are detailed in Part 1. These values for ΔG°t(H+) are then used to separate ΔG°t for the hydrogen halides to give values for ΔG°t for Cl–, Br– and I–; and the values for ΔG°t(Cl–) are used in turn to separate ΔG°t for salts MCl, where M+= Li+, Na+, K+, Rb+, Cs+ and Ag+. Values for ΔG°t for the hydrogen halides and for the salts are obtained from data available on the appropriate electrode potentials. Values for Kc=[(ButOH,H+)solv]/[H+aq][ButOHsolv] have been determined experimentally using the previously described spectrophotometric method with p-nitroaniline. The variations of ΔG°t with solvent composition for the single ions are compared with the variations for ΔG°t in other water + co-solvent mixtures and they are related to solvent structure in the mixtures: a maximum is found in ΔG°t(halide) and –ΔG°t(M+) at mole fractions of t-butyl alcohol ∼0.1.

Brillouin-Scattering Study of the Hypersonic Relaxation in tert.-Butanol-Water Mixtures

The acoustic relaxation of t-butanol-water mixtures in the GHz range is studied by the Brillouin scattering technique at l5°C, 25°C and 35°C with varying alcohol molar fraction x from 0 to 0.27. The sound velocity dispersion is observed at x≥0.057. The relaxation strength as a function of x possesses a maximum at x=0.2 (25°C) and the relaxational frequency increases with increasing x. The observed behavior of the relaxation is reasonably interpreted in terms of the dissociation equilibrium of H-bonded alcohol dimer with monomers by taking into account the effect of water and alcohol in the environment. The high-frequency limiting value of the absorption coefficient of this hypersonic relaxation is estimated, and is found to be much higher than the classical absorption due to shear viscosity.

Ion exchange in aqueous-organic solvents—II The invasion of electrolytes and distribution of metal ions in an anion exchanger: Water-methanol, -ethanol and -n-propanol

The invasion of hydrochloric acid of the strong base anion exchange resin Dowex 1 × 8 is determined in the mixed aqueous-methanol, -ethanol and -n-propanol solvents. From these data and measurements of the swelling of the resin, the mean ionic activities of hydrochloric acid in the resin phase are calculated. The invasion of hydrochloric acid is very much higher in the mixed solvents than in the aqueous solution and increases with increasing mole fraction of alcohol. The invasion of hydrochloric acid as a function of its concentration at constant mole fraction of ethanol (xs = 0·55) is found to increase linearly. The exchange distribution of thorium chloride as a function of the concentration of hydrochloric acid or lithium chloride is studied and it is found that the distribution of thorium is principally dependent on its sorption by invasion.

The surface tension and density of some hydrocarbon + alcohol mixtures at 303.15 K

The surface tension and density of the binary hydrocarbon+alcohol mixtures formed from ethyl alcohol, t-pentyl alcohol, benzene, toluene, cyclohexane, and methylcyclohexane were measured at 303.15 K. Hydrocarbon+ t-pentyl alcohol mixtures show the expected negative excess surface tension. Toluence+ethyl alcohol shows a positive excess surface tension, and the cycloalkane+ethyl alcohol mixtures show a minimum in the curve of surface tension against mole fraction at high mole fractions of alcohol. Surface concentrations and excesses were calculated by use of the Gibbs adsorption equation. The results indicate that ethyl alcohol is more strongly adsorbed at the surface of each mixture with a hydrocarbon than is t-pentyl alcohol. Excess volumes were calculated from densities and compositions and were found to be positive for all mixtures except ethyl alcohol+benzene and+toluene.

Thermodynamic properties of 2-propanol + 2-bromopropane mixtures

Excess enthalpies, excess Gibbs free energies, and excess volumes have been measured for 2-propanol + 2-bromopropane. The results indicate that the interaction of an alcoholic OH group with a CHBr group is of less importance than the interaction with a ketone group. This leads to stronger association of the alcohol in mixtures with 2-bromopropane than in mixtures with acetone, resulting in more positive excess enthalpies in the latter at high mole fractions of alcohol.

Comments on “the scattering of light and phase transition in solutions of tertiary butyl alcohol in water”

In two independent experiments, we have measured the Rayleigh factor of tert-butanol-water mixtures as a function of concentration. Our results are in strong disagreement with those of Vuks and Shurapova in that we find only a single maximum in the Rayleigh factor at mole fraction 0.125 in alcohol. We find that the Rayleigh factors of solutions in the immediate vicinity of 0.03 mole fraction of alcohol depend strongly upon the purity of the components and treatment of the solutions prior to measurement. A possible explanation for this behavior is given.

Lumry's law and the quenching of anthracene fluorescence by bromide in aqueoust-butyl alcohol

The Stern-Volmer quenching constant for the quenching of anthracene fluorescence by bromide at 298.15 K shows a complex dependence on alcohol mole fraction in water plust-butyl alcohol mixtures. A similar pattern is observed at other temperatures except near 285 K, the Lumry temperature for aqueous systems.

The Photochemically Produced Ketyl of Perfluorobenzophenone: Electron Spin Resonance Studies of Solvent Effects

The ketyl radical is formed when solutions of perfluorobenzophenone are photolyzed with u.v. light. The radical was identified by electron spin resonance (e.s.r.) studies of the effects of solvent, temperature, chemical exchange, and deuteration on the spectra. Solvent mixtures of cyclohexane and ethanol gave spectra which were very sensitive to the mole fraction of alcohol in the range 0–1%. An equilibrium constant for solvent molecule exchange has been deduced.

The scattering of light and phase transition in solutions of tertiary butyl alcohol in water

An additional maximum of light scattering is found in tert. butyl alcohol-water solution at the concentration 0.03 mole fraction of alcohol. At the same concentration a maximum for the specific heat and a minimum for the compressibility are situated. It is assumed that all these anomalies are caused by a phase transition in the solution. The additional maximum of light scattering is the result of fluctuations of the structure.

Heats of solution of KCl and structural features of aqueous solutions of n-propanol at 10 to 60�

oO ~ 0.3%. The AHsoln values were extrapolated graphically to infinite dilution (AHs~ln). The values of AHsoln are given in Table 1. The materials used for the investigation were a "chemically pure" grade of potassium chloride, recrystallized by the procedure given in [4], and a "chemically pure" n-propanol, which was distilled before preparing the water -alcohol mixtures. The concentration range studied of the aqueous n-propanol solutions was determined by the solubility and solution kinetics of the KC1. Figure 1 shows graphically the dependence of/%Fsoin on ~he composition of aqueous solutions of n-propanol, expressed as mole fractions of alcohol ~,, at all the temperatures studied.

Discontinuities in the surface structure of alcohol-water mixtures

Surface tension determinations by the capillary rise method were obtained, at 25 ‡C and at frequent concentration intervals, for two binary systems: methyl alcohol-water and ethyl alcohol-water. The data were plotted as a function of (γw−γa) Xba/(γw−γ) versus 100 Xba, where Xba denotes the mole fraction of alcohol in the bulk of the solution, and γw, γa, and γ are surface tensions of water, alcohol, and alcohol-water mixture, respectively.

Formation constants of cadmium chloride complexes in water–ethyl alcohol mixed solvents

The polarographic method was applied to the determination of overall formation constants of cadmium chloride complexes in water–ethyl alcohol mixed solvents. A 2M constant ionic strength LiClO4–LiCl system was employed and measurements were made at 0, 20, 40, 60, and 80% alcohol. Corrections for changes in ligand activity were made by potential measurements of the cell Ag–AgCl(8)|LiCl(x)′ LiClO4(2 –x)∥ reference electrode as the LiCl content was changed. The analysis indicated the successive formation of four mononuclear complexes at all alcohol contents.Correlations of log βi with mole fractions of non-aqueous solvent in the mixed solvent–electrolyte solutions are given. These correlations are equivalent to Tur'yans correlations of log βi with reciprocal dielectric constants. The mole fraction of alcohol is believed to be a better parameter than the dielectric constant of pure mixed solvents since the formation constants generally employed are evaluated at a finite ionic strength instead of infinite dilution.

Light scattering of sodium dodecyl sulphate in methanol-water mixtures

The effect of addition of methanol on the micellar behaviour of aqueous solutions of sodium dodecyl sulphate has been studied by light scattering measurements. At low alcohol concentration there is a small decrease in the critical micelle concentration but no change in micellar weight. With increasing alcohol concentration the critical micelle concentration increases and the micellar weight decreases, and at about a mole fraction of alcohol of 0.25 there is no evidence of micelle formation. Interpretation of the behaviour requires a knowledge as yet unknown of the part played by the changes in solvent structure and dielectric constant, and by the penetration of additive into the micelles.

Small Angle X-Ray Scattering from Tertiary-Butyl Alcohol-Water Mixtures

Abstract Small angle x-ray scattering measurements have been made on a number of t-butanol-water mixtures. The scattering is concentration dependent and has a maximum intensity for the solution with 0.11 mole fraction of alcohol. The zero angle scattering from this solution is temperature dependent and increases by a factor of 2.5 when the temperature changes from 5° to 56°C. Theoretical zero angle intensities, calculated from thermodynamic data in terms of the Kirkwood and Buff solution theory, were found to be in agreement with the experimental results. Thermodynamic data were also used to show that the solutions that give rise to appreciable small angle scattering also tend to form clusters of like molecules.

Ultrasonic absorption properties of solutions. Part 4.—t-Butyl alcohol + water mixtures

The ultrasonic absorption properties for t-butyl alcohol + water mixtures are reported over the frequency range 1.5–230 MHz and at 5, 25 and 45°. For those mixtures where the alcohol mole fraction was greater than 0.04 and less than 0.5, the relaxation curves have been analyzed using two relaxation frequencies. For some of these mixtures, the relaxation curves have also been analyzed using three relaxation frequencies. The lack of an excess absorption at low alcohol mole fractions is discussed in terms of a clathrate hydrate model. Possible contributing species to the relaxing equilibria at higher alcohol concentrations are examined.

Solvation spectra. Part 25.—Variation with temperature of absorption spectrum of iodide in aqueous t-butyl alcohol systems

The energy Emax of the first absorption maximum for iodide in water increases when t-butyl alcohol is added. At a fixed temperature Emax is a linear function of alcohol mole fraction x2 in the water-rich mixtures. The slope dEmax/dx2 of this plot has a maximum near 4 ° and is relatively insensitive to temperature over the range 30–40°, otherwise decreasing markedly with increase in temperature. A similar trend is observed in deuterium oxide solutions.

The sorption of rare earths on anion exchange resins from nitric acid-mixed solvent systems

The sorption of lanthanum, dysprosium, and ytterbium on anion exchange resins from nitric acid-isopropyl alcohol-water mixtures was studied in detail. The distribution function of lanthanum shows a maximum that appears to be caused by the invasion of isopropyl alcohol into the resin phase at high mole fractions of alcohol. This is supported by indirect evidence obtained from the effects of polarity of organic solvent, temperature, cross-linkage of resin, and complexing agent on the distribution functions. The size of the maximum decreases as the atomic number increases, and as a result, large differences in distribution coefficients are obtained at high mole fractions of alcohol. The separation of the rare earths by use of Amberlite IRA 400 resin and 0·5 M HNO 3-95 per cent isopropyl alcohol eluent is suggested.

Solution Hydrates of Aqueous Non-electrolytes

FRANKS and Johnson1 recently developed a computer method for the accurate determination of partial molar quantities from the measured total properties of binary systems. In their treatment of the volume of aqueous ethyl alcohol solutions, an unexpectedly complex and apparently anomalous variation of the ethyl alcohol partial molar volume was revealed at 0.06 alcohol mole fraction over the temperature-range 0°–30° C. In addition to the known2 increase of the water solvent partial molar volume and the decrease of the alcohol partial molar volume to a minimum at about 0.08 alcohol mole fraction, the alcohol partial molar volume-concentration contour furnished1 a hitherto unobserved change in course at 0.06 alcohol mole fraction appearing as a shoulder at 10° C. which progressively developed with increasing temperature to furnish a small but definite peak at 30° C.

The relation between the Margules and van Laar equations: The square‐root equation

AbstractThe excess free energy of mixing (ΔGE) has been used to show that the Margules and van Laar equations are reciprocally related. Thus if the Margules equation is written as χG = ΔGE/x1x2 = Σakx1k, then the van Laar equation can be written as χG−1 = Σbkx1k. It is known from previous work that the Margules equation does not adequately represent the thermodynamic properties of solutions of alcohols in non‐polar solvents over the whole range of composition, and it is pointed out that the van Laar equation cannot be used if the excess function changes sign. In such cases the use of a square‐root analogue of the Margules equation, χG = Σckx1(k‐2)/2, is proposed. This equation satisfactorily accounts for the rapid increase in χ as the mole fraction of alcohol becomes small and is empirically useful. However, it has theoretical disadvantages; it cannot be used to determine by extrapolation the value of the partial molar excess thermodynamic property for component 1 in an infinitely dilute solution; furthermore, it predicts a violation of the second law in the case of free energy of mixing for solutions dilute in component 1, but the region of violation lies outside the experimental range for x1 as low as 0.01.