Effect of Temperature on Henry's Constant in Simple Mixtures

Preston, G.T.; Funk, Edward W.; Prausnitz, John M.

doi:10.1080/00319107108083813

Cited by 8 publications

(4 citation statements)

References 1 publication

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“…Interestingly, constant density calculations exhibit a monotonic increase for β , unlike the calculations along the solvent saturation curve. This behavior supports previous macroscopic calculations by Prausnitz and co-workers . Furthermore, β for a given temperature is practically independent of the density.…”

Section: Monte Carlo Simulationsupporting

confidence: 91%

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Henry's Constant Analysis for Water and Nonpolar Solvents from Experimental Data, Macroscopic Models, and Molecular Simulation

et al. 2001

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Experimental data, equations of state (EoS), and Monte Carlo simulations are used to analyze the Henry's law constant of solutes in water and in organic solvents at different temperatures. EoS are incapable of correlating the experimental data for light hydrocarbons dissolved in water. Novel simulation methodologies are used for methane in water and in ethane. Results are analyzed with respect to the free energy of cavity formation for hosting the solute molecule in the solvent and the free energy of interactions between the solute molecule and the solvent. It is shown that the hydrophobic phenomenon is driven, to a large extent, by the weak intermolecular interactions between water molecules and nonpolar solute molecules. IntroductionThe Henry's law constant is used widely to describe the low solubility of light solutes in a variety of solvents at relatively low pressure over a wide temperature range. 1-3 Experimental data and accurate correlations have been reported for many solutes in different solvents such as water, 1 light and heavy hydrocarbons, 2,3 and others. 2 Typically Henry's constant increases with temperature for relatively low-temperature values, goes through a maximum, and then decreases for higher temperatures. A relatively high Henry's constant value corresponds to low solubility and vice versa. Traditionally, the low solubility of a solute in a solvent has been associated with differences in energetic interactions between solvent molecules and solute molecules or differences in molecular size or both. A typical example of the first case is the dissolution of n-alkanes in water. N-alkane molecules interact through weak London forces, whereas water molecules exhibit strong hydrogenbonding interactions resulting in three-dimensional structures. A representative example for the second case is that of light gases (hydrogen, nitrogen, etc.) dissolved in a heavy n-alkane.In this work, a generalized thermodynamic framework is presented for the analysis of the Henry's constant and its variation with temperature. Henry's constant is expressed as a product of two terms: The first term involves pure solvent thermodynamic properties only. The second term is a function of the excess chemical potential of the solute at the state conditions examined. The latter is subdivided into a term associated with the formation of a cavity in the solvent to host the solute molecule and a term that accounts for the free energy of inserting the solute into the cavity by turning on the energetic

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Section: Monte Carlo Simulationsupporting

confidence: 91%

“…This behavior supports previous macroscopic calculations by Prausnitz and co-workers. 29 Furthermore, µ solute ex,en for a given temperature is practically independent of the density. As expected, the difference is considerable in the case of the cavity formation term.…”

Section: Equation Of State Predictionsmentioning

confidence: 99%

Henry's Constant Analysis for Water and Nonpolar Solvents from Experimental Data, Macroscopic Models, and Molecular Simulation

et al. 2001

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“…That the behavior of Henry's constant is more fruitfully linked to the solvent density than to its temperature, has been suggested before (Preston et al, 1971;Potter and Clynne, 1978). Our results show this to be a thermodynamic necessity near the solvent's critical point.…”

Section: Critiquementioning

confidence: 87%

Gas solubility and Henry's law near the solvent's critical point

1989

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It has been experimentally observed, for water and nonaqueous solvents alike, that Henry's constant passes through a maximum and then declines as the temperature is raised from the triple point to the critical point. From classical and nonclassical models, we derive exact relations for the value of Henry's constant and its temperature dependence at the solvent's critical point, showing that the decline of this constant is a universal phenomenon. We demonstrate that the limiting temperature dependence of Henry's constant can be predicted from the thermodynamic properties of the pure solvent and the initial slope of the critical line. The validity of our prediction is tested by comparing it with experimental solubility data for several gases in high-temperature water and benzene. Our predictive model appears valid over a temperature range of at least 15% in temperature below the critical point of the solvent.

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“…Nonpolar gases display a minimum in their aqueous solubility with increasing temperature. The hydration enthalpy becomes positive above the solubility minimum temperature (52,53). For small hardsphere solutes, Gaussian theory (54) as well as the exact point-particle limit of the scaled particle theory (55) indicate that the sign of the hydration enthalpy is positive above the temperature of maximum density (TMD) of liquid water.…”

Section: (D) Shown Is the Ratio P N͞mentioning

confidence: 99%

Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

Rajamani

Truskett

Garde

2005

Proc. Natl. Acad. Sci. U.S.A.

275

329

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Small and large hydrophobic solutes exhibit remarkably different hydration thermodynamics. Small solutes are accommodated in water with minor perturbations to water structure, and their hydration is captured accurately by theories that describe density fluctuations in pure water. In contrast, hydration of large solutes is accompanied by dewetting of their surfaces and requires a macroscopic thermodynamic description. A unified theoretical description of these lengthscale dependencies was presented by Lum, Chandler, and Weeks [(1999) J. Phys. Chem. B 103, 4570 -4577]. Here, we use molecular simulations to study lengthscale-dependent hydrophobic hydration under various thermodynamic conditions. We show that the hydration of small and large solutes displays disparate dependencies on thermodynamic variables, including pressure, temperature, and additive concentration. Understanding these dependencies allows manipulation of the small-tolarge crossover lengthscale, which is nanoscopic under ambient conditions. Specifically, applying hydrostatic tension or adding ethanol decreases the crossover length to molecular sizes, making it accessible to atomistic simulations. With detailed temperaturedependent studies, we further demonstrate that hydration thermodynamics changes gradually from entropic to enthalpic near the crossover. The nanoscopic lengthscale of the crossover and its sensitivity to thermodynamic variables imply that quantitative modeling of biomolecular self-assembly in aqueous solutions requires elements of both molecular and macroscopic hydration physics. We also show that the small-to-large crossover is directly related to the Egelstaff-Widom lengthscale, the product of surface tension and isothermal compressibility, which is another fundamental lengthscale in liquids. molecular dynamics ͉ salt and additive effects ͉ density fluctuations ͉ nonpolar solvation B iological self-assembly processes in aqueous solutions are driven by water-mediated interactions between constituents taking part in the assembly. Of these, hydrophobic interactions have received particular attention because of their relevance to protein folding and interactions, micelle and membrane formation, and molecular recognition (1-5). Theoretical work in this direction has been focused on the modeling of primitive hydrophobic phenomena, such as hydration and association of small hydrophobic particles in water (6-13). However, biological assembly occurs over a spectrum of lengthscales from that of an amino acid to proteins and larger. Naturally, fundamental understanding of the lengthscale dependence of hydration and association of hydrophobic solutes in water will be relevant to the quantitative modeling of realistic macromolecular processes (14,15).Small hydrophobic solutes can be accommodated into the open hydrogen-bonded network of liquid water without significant perturbations. Indeed, theories that model density fluctuations over small lengthscales in pure water provide a quantitative description of the hydration thermodynamics of small...

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Effect of Temperature on Henry's Constant in Simple Mixtures

Cited by 8 publications

References 1 publication

Henry's Constant Analysis for Water and Nonpolar Solvents from Experimental Data, Macroscopic Models, and Molecular Simulation

Henry's Constant Analysis for Water and Nonpolar Solvents from Experimental Data, Macroscopic Models, and Molecular Simulation

Gas solubility and Henry's law near the solvent's critical point

Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

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