Ionic Heat Research Articles

Group Contribution Methods for Estimation of Ionic Liquid Heat Capacities: Critical Evaluation and Extension

AbstractRecently, new group contribution method (GCM) models have been developed for ionic liquids (ILs). However, difficulty arises in choosing an appropriate GCM for a given property estimation due to the fact that the reported accuracies do not enable meaningful comparison since they have been tested against different and limited datasets. Furthermore, many GCMs lack the parameters necessary to predict heat capacities for many new ILs. To overcome these problems, an extensive database of IL heat capacity data as a function of temperature was compiled and used to evaluate two different GCM approaches, analogously named the Meccano and Lego approaches, based on the nature of the fundamental building blocks used in each model. Although the Meccano approach was found to be slightly more accurate, the Lego approach has much broader applicability and is compatible with process simulation and IL design.

The Influence of Crystallization on the Ionic Conductivity of PEO/LiClO<sub>4</sub> Polymer Electrolytes

It’s generally accepted that the transport of lithium ions in solid polymer electrolytes exists mainly in the amorphous regions, thus the research has focused on reducing the crystallinity to obtain high conductivity at room temperature. However, the point has been challenged: crystalline systems can provide a better ionic conductivity. In this paper, PEO/LiClO4polymer electrolytes with different lithium-oxygen ratios were prepared by melt-blending. The results show that [EO]/ [Li+] = 3 system has higher ionic conductivity, 4.26×10-6S/cm, more than twice as that of [EO]/ [Li+] = 4 system. DSC and XRD results show PEO3:LiClO4crystalline phase present in both systems, the crystallinity of [EO]/ [Li+] = 3 system is higher. It illustrates the generally accepted mechanism is not suitable for these systems, suggesting the high conductivity of [EO]/ [Li+] = 3 system is due to the unique crystal structure of PEO3:LiClO4. Besides, as the crystallinity increases, the tensile strength of [EO]/ [Li+] = 3 system increases greatly, to 1.43 MPa. In addition, because of the high melt temperature of PEO3:LiClO4, the electrolytes will gain excellent heat resistance. In summary, this paper provides a new idea to prepare polymer electrolytes with high ionic conductivity, improved strength and excellent heat resistance in large scale.

Analytical Solutions of Ionic Diffusion and Heat Conduction in Multilayered Porous Media

Ionic diffusion and heat conduction in a multiple layered porous medium have many important engineering applications. One of the examples is the chloride ions from deicers penetrating into concrete structures such as bridge decks. Different overlays can be placed on top of concrete surface to slowdown the chloride penetration. In this paper, the chloride ion diffusion equations were established for concrete structures with multiple layers of protective system. By using Laplace transformation, an analytical solution was developed first for chloride concentration profiles in two-layered system and then extended to multiple layered systems with nonconstant boundary conditions, including the constant boundary and linear boundary conditions. Because ionic diffusion in saturated media and heat conduction are governed by the same form of partial differential equations with different materials parameters, the analytical solution was further extended to handle heat conduction in a multiple layered system under nonconstant boundary conditions. The numerical results were compared with available test data. The basic trends of the analytical solution and the test data agreed quite well.

Thermodynamic modeling of KCl + H2O and KCl + NaCl + H2O systems using electrolyte NRTL model

A comprehensive thermodynamic model based on electrolyte NRTL activity coefficient model is developed for KCl+H2O binary and KCl+NaCl+H2O ternary systems. To model KCl+H2O binary systems, we identify required binary interaction parameters for (K+Cl−):H2O pair by regressing experimental thermodynamic data including mean ionic activity coefficient, osmotic coefficient, vapor pressure, enthalpy, and heat capacity. To model KCl+NaCl+H2O ternary systems, we obtain required binary interaction parameters for (Na+Cl−):H2O pair from the literature and (K+Cl−):(Na+Cl−) pair by regressing available thermodynamic data including osmotic coefficient, vapor pressure, and solubility for KCl+NaCl+H2O ternary systems. The model accurately represents all thermodynamic properties with temperature from 273.15 to 473.15K and electrolyte concentration up to saturation. This model should be useful for process modeling and simulation of aqueous electrolyte solutions involving KCl.

Solid-state electrolytes based on ionic network polymers

Interpenetrating and semiinterpenetrating polymer networks are synthesized with the use of cationic and anionic ionic monomers: N�(3�(methacryloyloxy)propyl)� Nmethylpyrrolidinium bis(trifluoromethane� sulfonyl)imide, N�(2�(2�(2�(methacryloyloxy)ethoxy)ethoxy)ethyl)� Nmethylpyrrolidinium bis(fluorosulfo� nyl)imide, and (NbutylNmethylpyrrolidinium 1�(3�(methacryloyloxy)propylsulfonyl) (trifluoromethanesulfo� nyl) imide. Their ionic conductivities, electrochemical stabilities, heat resistances, thermal stabilities, and mechanical properties and the swelling of the films in ionic liquid/lithium salt mixtures were studied. The copoly� merization of N�(2�(2�(2�(methacryloyloxy)ethoxy)ethoxy)ethyl)� Nmethylpyrrolidinium bis(fluorosulfo� nyl)imide and poly(ethylene glycol dimethacrylate) and poly(ethylene glycol methacrylate) in the presence of butadiene-acrylonitrile rubber and a solution of Li(CF3SO2)2N in N�(methoxymethyl)� Nmethylpyrrolidinium bis(fluorosulfonyl)imide yielded a solidstate electrolyte wi th a set of properties optimum among the studied films: an ionic conductivity of 1.3 × 10 -4 S/cm (25°C), a tensile strength of 80 kPa, and an elongation at break of 60%.

Characteristics and oxidative stability of soy protein-stabilized oil-in-water emulsions: Influence of ionic strength and heat pretreatment

Some physicochemical characteristics, microstructure and stability of native and preheated (95 °C, 15 min) soy protein isolate (SPI)-stabilized emulsions, formed at varying protein concentrations (c; 0.5–4.0%, w/v) in the absence or presence of 300 mM NaCl, were characterized. The emulsifying ability, flocculated state of droplets, microstructure, interfacial protein concentration (Γ) of the fresh emulsions, as well as stability of these emulsions against coalescence, flocculation, creaming and even lipid oxidation upon storage up to 2 weeks were evaluated. In general, increasing c was favorable for the emulsification efficiency, but the flocculated state of oil droplets or size of the flocs in the fresh emulsions was more affected by the presence of salt, and/or the heat pretreatment. Increasing ionic strength or application of a heat pretreatment resulted in remarkable increases in extents of droplet flocculation in the fresh emulsions, as well as amount and concentrat,ion of adsorbed proteins at the interface. All the emulsions exhibited an extraordinary stability against coalescence and/or flocculation. Increasing c led to a progressive increase in stability against creaming, especially for the preheated SPI emulsions with 300 mM NaCl. All the emulsions at c = 1% or above exhibited a similarly high oxidative stability upon storage up to 9 days. Even at c = 0.5%, the oxidative stability of the formed emulsions could be greatly improved by increasing ionic strength, and/or application of a heat pretreatment. The findings have important implications for the development of an important kind of protein-stabilized emulsions with industrial relevance.

Dopamine-Mediated Sclerotization of Regenerated Chitin in Ionic Liquid.

Chitin is a promising structural material for biomedical applications, due to its many advantageous properties and abundance in nature. However, its usage and development in the biomedical field have been stagnant, because of chitin’s poor mechanical properties in wet conditions and the difficulties in transforming it into an applicable form. To overcome these challenges, we created a novel biomimetic chitin composite. This regenerated chitin, prepared with ionic liquid, showed improved mechanical properties in wet conditions by mimicking insect cuticle and squid beak sclerotization, i.e., catechol-meditated cross-linking. By ionic liquid-based heat treatment, dopamine oxidation produced melanin-like compounds and dopamine-meditated cross-links without any solvent evaporation and oxidant utilization. The dopamine-meditated sclerotization increased the ultimate tensile strength (UTS) of the regenerated chitin by 2.52-fold, measured after six weeks of phosphate-buffered saline (PBS) submersion. In addition, the linear swelling ratio (LSR) of the chitin film was reduced by about 22%. This strategy raises a possibility of using regenerated chitin as an artificial hard tissue in wet conditions.

Thermal analyses of LiFePO4/graphite battery discharge processes

An electrochemical–thermal coupling model is developed to describe the LiFePO4/graphite battery discharge and charge processes. Various heat generations/consumptions including Joule heat, reversible entropy heat, contact resistance heat, irreversible electrochemical reaction heat, ionic migration heat, and convective heat release to the ambient during charge or discharge processes are calculated in detail. The developed model is first validated by experimental data. Then systematic and comprehensive thermal analyses with respect to various discharge processes are performed based on the simulated results. For the specific cell considered, the irreversible electrochemical reaction heat and contact resistance heat are found to be the two main heat generation sources; for discharge processes of higher C-rate, the contact resistance heat take more proportion of the total heat generation as it is directly proportional to the squared discharge current density; the ionic migration heat is a sink with magnitude being about 1/3 of the Joule heat. The reversible entropy heat changes its sign from a negative heat sink to a positive heat source during a discharge process and its changing magnitude may be comparable to the irreversible electrochemical reaction heat for all the discharge processes of different C-rates.

Simulation of heat generation in a reconstructed LiCoO2 cathode during galvanostatic discharge

A three dimensional numerical framework with finite volume method was employed to simulate heat generation of a semi lithium ion battery (LIB) cell during isothermal galvanostatic discharge processes. The microstructure of the LIB cathode electrode was experimentally determined using X-ray nano computed tomography technology. Heat generation in the semi LIB cell during galvanostatic discharge processes from different mechanisms, such as electronic resistive heat, ionic resistive heat, contact resistive heat, reaction heat, entropic heat and heat of mixing, was investigated. The spatial distribution of heat generation rates from different mechanisms was also studied. The simulation results demonstrate that the magnitude of heat generation rates spans a wide range in the electrode due to structural inhomogeneity. The simulation results of heat generation from the three dimensional model and the porous-electrode theory model were compared in this study. It is found that the typical Bruggeman coefficient, 1.5, underestimated ionic resistance in the electrolyte and overestimated electronic resistance in the cathode particles. In general, the three dimensional model predicted more heat generation than the porous-electrode theory model at large discharge rates due to the wider distribution of physical and electrochemical properties.

Design and performance evaluation of ionic liquid-based microwave-assisted simultaneous extraction of kaempferol and quercetin from Chinese medicinal plants

An ionic liquid-based microwave-assisted extraction (IL-MAE) technique has been successfully developed for the simultaneous effective extraction of quercetin and kaempferol from Toona sinensis and Rosa chinensis which are Chinese medicinal plants. Twenty different types of ionic liquids (ILs) with different cations and anions have been synthesized and investigated. Several significant operating parameters of IL-MAE were optimized by a series of single factor experiments and orthogonal design L9 (34) experiments, respectively. Compared with ionic liquid-based maceration extraction (IL-ME), ionic liquid-based heat extraction (IL-HE) and ionic liquid-based ultrasound-assisted extraction (IL-UAE), the optimized approach was demonstrated as the optimal technique with the highest extraction efficiency and the shortest extraction time. Reversed phase high performance liquid chromatography (RP-HPLC) with ultraviolet-detection (UV-DAD) was employed for the simultaneous analysis of kaempferol and quercetin. The results indicated that the extraction amounts of quercetin from Toona sinensis extracted using [Bmim]Br and from Rosa chinensis extracted using [Omim]Br were 176.5 mg g−1 with RSD 1.2% and 134.3 mg g−1 with RSD 0.63%. And the extraction amounts of kaempferol from Toona sinensis extracted using [Bmim]Br and from Rosa chinensis extracted using [Omim]Br were 16.12 mg g−1 with RSD 0.24% and 9.070 mg g−1 with RSD 0.15%. The developed approach for analyzing quercetin was linear between the concentrations of 32.10 mg L−1 to 233.3 mg L−1 in Toona sinensis and 25.70 mg L−1 to 160.5 mg L−1 in Rosa chinensis with the regression coefficients (R) of 0.9998 and 0.9999, respectively. And for kaempferol, the developed approach was linear between the concentrations of 0.73 mg L−1 to 23.20 mg L−1 in Toona sinensis and 0.19 mg L−1 to 15.00 mg L−1 in Rosa chinensis with the regression coefficients (R) of 0.9993 and 0.9996, respectively. The recoveries of quercetin extracted by the developed methods were 96.76–104.1% in Toona sinensis and 98.40–103.3% in Rosa chinensis, and the recoveries of kaempferol were 95.75–106.3% in Toona sinensis and 98.55–102.9% in Rosa chinensis with the RSDs of lower than 3.0%. The LODs were 1.87–2.26 μg mL−1. The microstructures and chemical structures of these two researched samples before and after different extraction procedures were also investigated.

Processes, parameters and mechanisms controlling the normal and abnormal growth of porous anodic alumina films

Aluminium was anodised in H2SO4 solutions 0.25–1.53 M, temperatures 0–35 °C, times up to 90 min and voltage 25 V. Anodising was followed chronoamperometrically. The passing charge, consumed Al, formed oxide, transport numbers of oxygen anions in barrier layer and film thicknesses were determined. Films were examined to detect abnormal film growth, called burning. It was found that the current in Al anode is closely solely ionic, and the only processes occurring are those related with ionic charge transport and heat release and its abduction for which suitable equations were formulated relating many parameters. At each concentration, the temperatures, current densities and times up to which normal film growth occurs and above which stain-like mild, island-like intermediate, strong, strong-destructive and mixed burning appears were found. Burning emerges at lower concentrations, temperatures and times for thinner Al. Low concentrations and temperatures among thresholds where mild and next-kind burning first appear define windows of conditions where thick enough dark or black films grow. Peculiar chronoamperometric plot characterises each film growth type. Though other burning kinds can appear at each surface region or in the whole surface, strong and strong-destructive emerge only at the lower Al side around which the efficiency of solution stirring is highest. The mechanisms of normal and abnormal film growth were formulated showing that different processes and interacting variable parameters, some of which are noted for first time, regulate each film growth type. These can predict methods to avoid abnormal film growth.

Application of ionic liquid-based surfactants in the microwave-assisted extraction for the determination of four main phloroglucinols fromDryopteris fragrans

An ionic liquid-based surfactant combined with microwave-assisted extraction method, followed by RP-HPLC-diode array detection (DAD) with a core shell column, was successfully applied in extracting and quantifying four major phloroglucinols from Dryopteris fragrans. Eight ionic liquids with different cation and anion were investigated, and 1-octyl-3-methylimidazolium bromide presented the best relative extraction efficiency for four phloroglucinols. The optimum conditions of this method were as follows: ionic liquid concentration 0.75 M, liquid/solid ratio 12:1 mL/g, extraction time 7 min, extraction temperature 50°C, and irradiation power 600 W. The quality analytical parameters of the method were obtained based on the linearity, precision, accuracy, detection, and quantification limits. The recoveries were between 96.90 and 103.5% with standard deviations not higher than 4.7%. Compared with ionic liquid-based heat reflux extraction, ultrasonic-assisted extraction, negative-pressure cavitation extraction, and conventional microwave-assisted extraction, the relative extraction efficiencies of the proposed method for four phloroglucinols increased 1.5-40.4%. The method was successfully applied for the quantification of four major phloroglucinols from D. fragrans. All these results suggest that the developed method represents an excellent alternative for the extraction and quantification of phloroglucinols in other plant materials.

Ultrasonic Properties of Hydrophobic Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids

Energy conversion in sonochemistry is known to be an important factor for understanding the mechanism of chemical reactions. However, ultrasound characteristics are dependent on the physical properties of the liquid medium. This work describes specific heat capacities (cp) of five hydrophobic bis(trifluoromethylsulfonyl)imide based ionic liquids ([C8mpyrr][NTf2], [C4mpyrr][NTf2], [C8epip][NTf2], [C8mim][NTf2], [C8mpy][NTf2]) and, for the first time, the acoustic power when they are submitted to ultrasound at two selected electric powers. The behavior of ultrasound in ionic liquids is then compared to the one in water. Despite the difference in cp values, the measured acoustic powers are very similar for both media. Indeed, ionic liquids heat up faster than water, and this can lead to interesting effects when using ionic liquids as solvents in organic chemistry.

Thermodynamic representation of the NaCl + Na 2SO 4 + H 2O system with electrolyte NRTL model

A comprehensive thermodynamic model based on the electrolyte NRTL (eNRTL) activity coefficient equation is developed for the NaCl + H 2O binary, the Na 2SO 4 + H 2O binary and the NaCl + Na 2SO 4 + H 2O ternary. The NRTL binary parameters for pairs H 2O–(Na +, Cl −) and H 2O–(Na +, SO 4 2−), and the aqueous phase infinite dilution heat capacity parameters for ions Cl − and SO 4 2− are regressed from fitting experimental data on mean ionic activity coefficient, heat capacity, liquid enthalpy and dissolution enthalpy for the NaCl + H 2O binary and the Na 2SO 4 + H 2O binary with electrolyte concentrations up to saturation and temperature up to 473.15 K. The Gibbs energy of formation, enthalpy of formation and heat capacity parameters for solids NaCl (s), NaCl·2H 2O (s), Na 2SO 4(s) and Na 2SO 4·10H 2O (s) are obtained by fitting experimental data on solubilities of NaCl and Na 2SO 4 in water. The NRTL binary parameters for the (Na +, Cl −)–(Na +, SO 4 2−) pair are regressed from fitting experimental data on dissolution enthalpies and solubilities for the NaCl + Na 2SO 4 + H 2O ternary.

Characterization and Quantification of Electronic and Ionic Ohmic Overpotential and Heat Generation in a Solid Oxide Fuel Cell Anode

The development of a solid oxide fuel cell (SOFC) with a higher efficiency and power density requires an improved understanding and treatment of the irreversibilities. Losses due to the electronic and ionic resistances, which are also known as ohmic losses in the form of Joule heating, can hinder the SOFC’s performance. Ohmic losses can result from the bulk material resistivities as well as the complexities introduced by the cell’s microstructure. In this work, two-dimensional (2D), electronic and ionic transport models are used to develop a method of quantification of the ohmic losses within the SOFC anode microstructure. This quantification is completed as a function of properties determined from a detailed microstructure characterization, namely, the tortuosity of the electronic and ionic phases, phase volume fraction, contiguity, and mean free path. A direct modeling approach at the level of the pore-scale microstructure is achieved through the use of a representative volume element (RVE) method. The correlation of these ohmic losses with the quantification of the SOFC anode microstructure are examined. It is found with this analysis that the contributions of the SOFC anode microstructure on ohmic losses can be correlated with the volume fraction, contiguity, and mean free path.

Application of ionic liquids in the microwave-assisted extraction of podophyllotoxin from Chinese herbal medicine

A micelle-mediated extraction technique, i.e. ionic liquid-based microwave-assisted extraction (ILs-MAE) technique has been developed for the effective extraction of podophyllotoxin from three Chinese medicinal plants. Several operating parameters were successively optimized by single-factor and L(9) (3(4)) orthogonal array experiments. 1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]), 1-decyl-3-methylimidazolium tetrafluoroborate ([demim][BF(4)]) and 1-allyl-3-methylimidazolium tetrafluoroborate ([amim][BF(4)]) were selected as the optimal surfactants for Dysosma versipellis, Sinopodophyllum hexandrum and Diphylleia sinensis, respectively. Compared with other extraction techniques, such as ionic liquids-based maceration extraction (ILs-ME), heat extraction (ILs-HE) and ultrasound-assisted extraction (ILs-UAE), the ILs-MAE technique not only took a shorter time but also afforded a higher extraction rate of podophyllotoxin from the herbs. Reversed phase high performance liquid chromatography was employed for the analysis of podophyllotoxin. The results showed that the linearity for analyzing podophyllotoxin in all three herbs was in the concentration range of 0.005-0.4 mg mL(-1) with the correlation coefficient between 0.9993 and 0.9996. LODs were 2.05-2.58 μg mL(-1) and RSDs of inter-day stability were less than 5.8%. Repeatability and intermediate precision were separately lower than 3.3% and 6.3%. The recoveries for podophyllotoxin extracted with the ILs-MAE technique were in the range of 97.1-102% and all RSDs were lower than 3.0%. Furthermore, the mechanism of ILs-MAE was preliminarily studied by means of kinetic mechanism, surface structures and chemical compositions of samples before and after different extraction techniques. On the basis of the destruction of herb surface microstructures and high solubility of ILs, the ILs-MAE technique eventually got the maximum yield value.

Uptake and desorption of nickel(II) using polymerised tamarind fruit shell with acidic functional groups in aqueous environments

The sorption potential of formaldehyde polymerised tamarind fruit shell (FPTFS) containing acidic functional groups for the treatment of Ni(II) ions from aqueous solutions has been investigated. The adsorbent was characterised by infrared spectroscopy and scanning electron microscopy. Operating parameters affecting Ni(II) adsorption were investigated by the batch technique. Maximum Ni(II) sorption was found to occur at an initial pH of around 6. Kinetic studies showed that the amount adsorbed increased with initial Ni(II) concentration and the equilibrium was established in 180 min. The kinetic data were analysed using the Lagergren pseudo-first-order, Ritchie second-order and modified Ritchie second-order equations, and showed better fit with the modified Ritchie second-order equation. Equilibrium data were analysed by Langmuir, Freundlich, Sips and Toth isotherm models and the Sips model best defined the isotherm. The adsorption of Ni(II) was endothermic in nature (ΔHads: 45.93 kJ/mol) with an increase in entropy (ΔSads: 245.67 J/mol/K) and a decrease in Gibbs free energy (ΔGads:−28.52 to−35.67 kJ/mol) in the temperature range 30–60 °C. The reduction in adsorption capacity with an increase in ionic strength and isosteric heat of adsorption (ΔHx: 24.85 kJ/mol) revealed an ion exchange mechanism for Ni(II) adsorption. The adsorption efficiency of FPTFS towards Ni(II) removal from a nickel-plating industry wastewater sample was investigated and quantitative removal of 100 mg/L of Ni(II) in 1 L of industrial wastewater was possible with 6 g of FPTFS. The spent, nickel-laden FPTFS was regenerated by 0.1 M HCl and four adsorption/desorption cycles were performed. The results indicated that FPTFS exhibited considerable potential for application in the removal of Ni(II) ions from aqueous solutions.

Classical Transport in a Plasma

An ideal plasma of electrons and a single species of ions in the low collisionality limit subject to an almost straight magnetic field is considered. In such conditions, the linear theory of transport determines the 3 × 1 matrix of dissipative fluxes [J with circumflex above]r namely, the electric current, the electronic heat flux and the ionic heat flux, in terms of a 3 × 1 matrix of thermodynamic forces [X with circumflex above] combining the electric field with the gradients of the densities and of the temperatures. The classical transport coefficients are the components of the 3 × 3 matrix of tensors [L with circumflex above]rs of the linear flux-force relations [J with circumflex above]r = [summation from s=1 to 9][L with circumflex above]rs[X with circumflex above]. The theory is developed in the framework of the statistical mechanics of charged particles starting from the Landau kinetic equation.

Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni-18Cr-6Fe Alloys

Abstract The breakdown potentials of mill-annealed Ni-18Cr-6Fe alloys were measured in wide range of chloride concentrations (0.001–1 M NaCl) and various concentrations of thiosulfate ranging from 0–0.25 M (Na2S2O3) at 80°C using the potentiodynamic technique. These potentials were compared with heat treated alloys for one or five hours at 900°C (and quenched). This work aimed to study the effect of sensitization on the pitting characteristics of this alloy in chloride-thiosulfate solutions. The anodic polarization curves revealed that sensitized alloys became more susceptible to chloride and thiosulfate pitting attack, or both. Addition of thiosulfate was potentially detrimental to chloride pitting resistance and the aggressiveness of thiosulfate species was found dependent on the ratio of chloride to thiosulfate concentration as the overall ionic strength is varied. A thiosulfate to chloride ratio of 1:40 (S2O2–3 / Cl–=0.025) was found be the most aggressive, regardless of ionic strength or heat treatment duration.

Molar Volumes and Heat Capacities of Electrolytes and Ions in N,N-Dimethylformamide

Densities and heat capacities of various 1:1 and higher-charged electrolytes have been measured in N,N-dimethylformamide (DMF) at 25 degrees C using a series-connected flow densimeter and Picker calorimeter. Standard molar volumes V (o) and isobaric heat capacities C p (o) derived from these data were split into their ionic contributions using the tetraphenylphosphonium tetraphenylborate (TPTB) reference electrolyte assumption. The values so obtained have enabled a meaningful separation of the effects of cationic size and charge for the first time in a nonaqueous solvent. As in water, V (o)(M (n+) ) values in DMF are markedly more negative for higher-charged cations due to increasing electrostriction of the solvent. In contrast, ionic charge has a much smaller effect on C p (o)(M (n+) ) in DMF than in water. Ionic volumes in DMF show the expected dependence on size but those of small monatomic monovalent cations and anions imply a significant difference in accessibility of the electron donor and acceptor sites on the DMF molecule. Ionic heat capacities in DMF show a relatively weak dependence on ionic size that, when corrected for charge, is opposite to that in water. Both V (o)(R 4N (+)) and C p (o)(R 4N (+)) in DMF show the usual linear dependence on carbon number but differ from their values in aqueous solution due to the absence of hydrophobic interactions in DMF.