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Data on the solubility of neutral compounds in perfluoro-hexane, -heptane, and –octane have been obtained from the literature. It is shown that water-solvent and gas-solvent partition coefficients, P and K respectively, are effectively the same for all three perfluoroalkanes. Linear free energy relationships, LFERs, have been set up for these partition coefficients, as log P and log K. Comparison of the LFER coefficients in the log K equation for perfluoroheptane with those for a large number of other solvents shows that perfluoroheptane is an unusual solvent, in that small nonpolar solutes are more soluble than in other solvents. The comparative solubility of small nonpolar gaseous compounds in perfluoroheptane is due to a combination of cavity and interaction terms. Calculations using Pierotti's version of Scaled Particle Theory indicates that the solute-perfluoroheptane unfavourable cavity term is always smaller than that for solution in other solvents, which by itself would lead to enhanced solubilities in perfluoroheptane, as shown by small nonpolar solutes. As the solute becomes larger and more polar, the favourable interaction terms in other organic solvents become much larger than the corresponding interaction terms in perfluoroheptane. This results in the larger and/or more polar gaseous solutes being much more soluble in other organic solvents than in perfluoroheptane.

Excess molar volumes V (E) for 40 mixtures of heptane with a liquid alkane and apparent molar volumes in heptane for eight solid alkanes have been obtained at 298.15 K. They include five linear, 30 branched-chain, and 13 cyclic alkanes. Almost all systems exhibit negative V (E) values. For mixtures with open chain alkanes, V (E) increases from C5 to C7 and then decreases. A similar trend is shown by mixtures with cycloalkanes. V (E) values are compared with known H (E) data for mixtures with heptane and tetrachloromethane. Signs and trends of V (E) and H (E) are correlated with the free volume and interactional terms of the Flory theory. The partial molar volumes at infinite dilution in heptane, VA degrees, have also been obtained and discussed together with literature data on other hydrocarbons and polar compounds. The calculated contributions to VA degrees by CH3, CH2, CH and C groups are compared with previously determined contributions of polar groups. The lower contributions of the latter groups are explained with the volume contraction caused by dipole-induced dipole interaction. The volume effects associated with branching and cyclization have been evaluated and compared with the corresponding effects on solvation enthalpy. The branching effect, in the order of magnitude of few cm(3)center dot mol(-1), and the larger negative values of cyclization volumes, down to -24 cm(3)center dot mol(-1), are discussed in terms of packing and solute-solvent interactions, in analogy to polar organic solutes either in heptane and tetrachloromethane. A negative cyclization effect is also exhibited by the solvation enthalpies.

Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of {heptane + open chain secondary (diethyl to dibutyl) and tertiary (triethyl to tripentyl) amines} as well as for cyclic imines (C2, C3, C4, C6, and C7) and primary cycloalkylamines (C5, C6, C7, and C12). The VE values were found positive for mixtures involving small size amines, with VE decreasing as the size increases. Negative VE’s were found for tributyl- and tripentylamine, heptamethylenimine, and cyclododecylamine. Mixtures of heptane with cycloheptylamine showed an s-shaped curve. Partial molar volumes V ∘ of amines at infinite dilution in heptane were obtained from VE and compared with V ∘ of hydrocarbons and other classes of organic compounds taken from literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, NH, N, OH, O, CO, and COO) contributions to V ∘ . These contributions, the effect of cyclization on V ∘ , and the limiting slope of the apparent excess molar volumes were discussed in terms of solute–solvent and solute–solute interactions.

Partial molar enthalpies and excess enthalpies HE of binary mixtures of heptane + secondary and tertiary n-alkyl, primary cycloalkyl, and secondary (hetero)cyclic amines have been determined at 298.15 K by isothermal titration calorimetry in the whole composition range. All mixtures showed positive HE values which decrease with increasing amine size in each category, and decrease in the order cyclic primary > cyclic secondary > linear primary [1] > secondary > tertiary when comparing amines of similar size in different categories. From partial molar enthalpies at infinite dilution and known enthalpies of vaporization, the solvation enthalpies have been calculated either for heptane in amines and for amines in heptane. These quantities, together with their cavitational and interactional terms obtained applying the scaled particle theory, are discussed to get insight into the types and relative strength of solute–solvent interactions and into their effects on molecular structure features such as branching and cyclization.

Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of heptane + primary n-alkyl (C3 to C10) and branched amines (iso-propyl-, iso-, sec-, and tert-butyl-, iso-, tert-pentyl-, and pentan-3-amine) in the whole composition range. The apparent molar volumes of solid dodecyl- and tetradecylamine in heptane dilute solution were also determined. The VE values were found positive for mixtures involving C3 to C8 linear amines, with VE decreasing with chain lengthening. Heptane + nonyl and decylamine showed s-shaped, markedly asymmetric, curves. Mixtures with branched C3 to C5 amines displayed positive VE’s larger than those observed in the mixtures of the corresponding linear isomers. Partial molar volumes V° at infinite dilution in heptane were evaluated for the examined amines and compared with those of alkanes and alkanols taken from the literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, and OH) contributions to V°. The effect of branching on V° and the limiting slope of the apparent excess molar volumes were evaluated and discussed in terms of solute–solvent and solute–solute interactions.

Vapour–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and excess enthalpies (HE) of binary mixtures of perfluoro-n-hexane plus an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether), have been determined using a head-space gas-chromatographic technique, a turbidimetric apparatus, and a heat-flow calorimeter, respectively. A recently designed titration technique and calculation procedure have been used to obtain HE from heats of solution. The observed liquid–liquid coexistence curves have been compared with those predicted by the activity coefficients γi and their temperature dependence. All mixtures are strongly endothermic (HE > 0) and show large positive deviations from ideality (GE > 0), which increase with the size of the ether. Molecular interactions have been examined by calculating and discussing solvation functions and Kirkwood–Buff (KB) integrals. Perfluorohexane proved to be an inert molecule that interacts with ethers more weakly than hexane.

The excess molar volumes V m E at T =298.15 have been determined in the whole composition domain for (2-methoxyethanol + tetrahydrofuran + cyclohexane) and for the parent binary mixtures. Data on V m E are also reported for (2-ethoxyethanol + cyclohexane). All binaries showed positive V m E values, small for (methoxyethanol + tetrahydrofuran) and large for the other ones. The ternary V m E surface is always positive and exhibits a smooth trend with a maximum corresponding to the binary (2-methoxyethanol + cyclohexane). The capabilities of various models of either predicting or reproducing the ternary data have been compared. The behaviour of V m E and of the excess apparent molar volume of the components is discussed in both binary and ternary mixtures. The results suggest that hydrogen bonding decreases with alcohol dilution and increases with the tetrahydrofuran content in the ternary solutions.

Excess molar volumes VE at 298.15 K have been determined by means of a vibrating-tube densimeter for binary mixtures of n-hexane with a perfluoroalkane, C5–C8, and of perfluorohexane with a n-alkane, C5–C8, or an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether). The systems perfluoropentane+hexane, perfluorohexane+pentane or hexane or diethyl ether have been investigated in the entire mole fraction range, while the other mixtures only in the miscibility regions. The observed VE values are positive (up to 5.5 cm3 mol−1) and among the largest known for non-electrolyte systems. Limiting partial molar volumes, V ° , have been evaluated for each component of the examined mixtures. The behaviour of V ° has been discussed in terms of the scaled particle theory (SPT) and of a simple group additivity scheme based on surface interactions. An estimate has been made of the average separation distance of solvent from solute molecules.

Vapour–liquid equilibria (VLE) of binary mixtures of n -perfluorohexane plus a n -alkane (C 5 –C 8 ) and of n -hexane plus a n -perfluoroalkane (C 5 –C 8 ) were determined using a head-space gas-chromatographic technique. Excess molar Gibbs energies, G E , for the systems investigated have been obtained by a least-square treatment of equilibrium data. Liquid–liquid equilibria (LLE) were determined by turbidimetry for n -perfluorohexane+ n -C n H 2 n +2 ( n =6–8) mixtures and the observed T – x curves compared with those predicted by the temperature dependence of activity coefficients. All mixtures show strong positive deviations from ideality, which increase with the size of the second component. Solute–solvent and solute–solute interactions have been examined by calculating and discussing solvation Gibbs energies and Kirkwood–Buff integrals. Perfluoroalkanes proved to be inert molecules that interact weakly with themselves as well as with alkanes.

Excess molar volumes VmEof {di- n -butyl ether (DBE) + a monofunctional organic compound} have been determined atT = 298.15 K over the whole composition range by means of a vibrating-tube densimeter. TheVmE values were either positive (propylamine, or butylamine, or acetone, or tetrahydrofuran + DBE) or negative (methanol, or butanol, or diethyl ether, or cyclopentanone, or acetonitrile + DBE). Markedly asymmetric VmEcurves were displayed by (DBE + methanol) and (DBE + acetonitrile). Partial molar volumes __ Vmoat infinite dilution in DBE, both from this work and the literature, were analysed in terms of an additivity scheme, and the group contributions thus obtained were discussed and compared with analogous results in water. DBE revealed a greater capability of distinguishing between polar and non-polar solutes, as well as in discriminating differently shaped molecules (unbranched, branched, cyclic). The limiting slopes of apparent excess molar volumes are evaluated and briefly discussed in terms of solute–solute and solute–solvent interactions.

A calorimetric technique and a calculation procedure to obtain excess enthalpies HE of liquid mixtures is described and tested. It is based on a heat-flow calorimeter used as a titration calorimeter to measure the heat effects associated to small additions of one of the components, or a mixture of them, to the ampoule containing a known amount of the other component or of a mixture of them. The procedure takes into account the presence of a small vapour space and calculates the heat involved in the vapour–liquid equilibration after each addition. The experimental values are fitted with a parametric equation such as Redlich–Kister to determine the HE parameters by least-squares adjustment. The technique has been tested with respect to the systems ethanol+cyclohexane, dioxane+water and tetrachloromethane+benzene. The results show a good agreement with literature data for these mixtures, and confirm the capability of this technique to reliably replace the mix-flow technique when the components mix slowly, or show a mixture gap, or are available in small quantities. HE results are reported for the system perfluorohexane+hexane for which the mixing process is slow.

The partial molar enthalpy H at 323.15K of each component (solvaton) of the ternary systems ethanol + trichloromethane (TCM) + dioxane, methanol + TCM + acetone and ethanol + TCM + n-heptane is analyzed in order to estimate the relative weight of the contributions due to: i) the interactions between solvaton and pure solvents; ii) a local composition in the neighbourhood of the solvaton that is different from the bulk one; iii) specific solvaton-solvent and solvent-solvent interactions. These systems have been chosen because present a wide range of the strength of interactions that can take place between the same or different species: hydrogen bonds, dipole-dipole and dispersion. This analysis is carried out by using the Kirkwood-Buff theory to calculate the local composition and the results as regards this quantity are presented and discussed. The results of the whole treatment indicate that non-zero excess local composition is the main cause of the H trend when the solvaton is alcohol dissolved in the binary mixture of alcohol + TCM, alcohol + heptane and TCM + heptane. This contribution is also effective but to a smaller extent for dioxane in ethanol + TCM, for acetone in methanol + TCM, and for heptane in ethanol + heptane. For ethanol infinitely diluted in dioxane + TCM and for methanol also at infinite dilution in acetone + TCM, the particular trends of H are not due non-zero excess local composition in the neighbourhood of the solvatons, but to solvent-solvent association through hydrogen bonding which allows a favourable solvaton-solvent interaction. In the other cases, the H trend is mostly determined by the same interactions that take place in the solution of the solvatons with the neat substances. The present study indicates that for excess local composition to play a significant role in determining H , one of the solvent components needs to be able to self-associate through hydrogen bonding.

By means of a vibrating tube densimeter, the excess molar volumes V E at 298.15 K have been determined in the whole composition domain for the ternary system ethanol+tetrahydrofuran+cyclohexane and for the relevant binary mixtures. While ethanol+tetrahydrofuran shows slight V E values and a S-shaped V E curve, the other two binaries have similar largely positive V E s. The ternary V E surface is almost always positive with a small maximum. The binary V E data have been described with different correlation equations. The capabilities of different models of either predicting or reproducing the ternary data have been compared. The behaviour of V E and of the partial molar excess volumes of the components in the ternary system is discussed and it is found that hydrogen-bonding decreases with alcohol dilution and increases with the tetrahydrofuran solution content.

A systematic study of a series of room-temperature ionic liquids, belonging to the alkylammonium nitrate family (XAN), was carried out at 298.15 K and 0.1 MPa with the aim of investigating the effect of the cationic chain length on some thermo-physical properties and their behavior in the organic solvent N-methyl-2-pyrrolidone (NMP), over the whole concentration range. Experimental densities were used to calculate molar volumes, V-m, and excess molar volumes, V-E. Complementary information was obtained by isothermal titration calorimetry that provided the values of the heat of mixing, H-E, and the excess partial molar enthalpies of each component, (H) over bar (E)(1) and (H) over bar (E)(2). The density values of neat XAN samples decreased as the alkyl chain length of the cation increases, whereas, the addition of the methoxy group to the considered smaller alkyl chain resulted in an increase of density. Negative V-E and H-E values were found for each XAN + NMP system, indicating the presence of strong attracting interactions between the constituents. (C) 2014 Elsevier B.V. All rights reserved.

It is shown that a reference state is necessary for the correct interpretation of the Kirkwood−Buff integrals, Gij, of liquid mixtures in terms of interactions between the components and for their use in the calculation of the local composition. This state is identified with the symmetrical ideal system, and its Gij's are taken as zero-level. The equations for calculating the Gij of the reference mixtures are derived and discussed, and those for calculating local composition and preferential solvation are reformulated with respect to the reference system. The mixtures of compounds with large size mismatch and/or small deviations from Raoult's law are those for which the new equations should be applied in order to get correct indications on the interactions that take place and influence the preferential solvation. A comparison with Flory−Huggins athermal mixtures (GE = −TSE) as reference systems is also made, allowing one to estimate the relative weights of the contributions to Gij and preferential solvati...

Vapour-liquid equilibria for the ternary system ethanol + tetrahydrofuran + cyclohexane and for the relevant binary mixtures have been determined at 298.15 K by head-space gas-chromatographic analysis of the vapour phase directly withdrawn from an equilibration apparatus. Experimental data have been described with different equations (Redlich-Kister, Wilson, NRTL and UNIQUAC) and excess Gibbs energies GE as well as activity coefficients γi of components have been obtained. All systems exhibit positive deviations. The binaries containing cyclohexane form azeotropic mixtures at 298.15 K, while ethanol + tetrahydrofuran and the ternary systems do not. The excess entropy and the temperature dependence of GE and γi have been calculated in the whole ternary domain from the known excess enthalpy and heat capacity.

Densities and viscosities of binary mixtures (H2O or D2O) (1) + (DMSO or DMSO-D6)(2) have been measured over the entire mole fraction range; and the excess volumes, excess viscosities, and excess partial molar volumes Vf of the components have been obtained. All systems show negative excess volume Ve at all compositions, values for mixtures containing D2O being more negative than those with H2O byca. 0.03 cm3-mol-1 at x1, = 0.6, where a minimum is observed. The difference between DMSO and DMSO-D6 containing mixtures is negligible. The excess viscosity ηe is always positive and shows a maximum at x1 = 0.65; at this composition, the substitution of H2O with D2O causes an excess viscosity increment ofca. 0.35 mPa-s, while deuteration of DMSO brings about a smaller increase,ca. 0.1 mPa-s. The trend of V2E with concentration shows the characteristic features of moderately hydrophobic solutes in water (negative values and a minimum in the water-rich region), features that are slightly but significantly more marked in D2O than in H2O. The V2E values in the water-diluted region and at x1, =0 are more negative for D2O than for H2O.

Excess enthalpies and excess heat capacities at 298.15 K for the ternary system ethanol + dimethylformamide + tetrahydrofuran were determined by means of a flow calorimetric apparatus built in our laboratory. Experimental data were described with a Redlich-Kister type equation and compared with those of other ternary systems previously studied (ethanol + tetrahydrofuran + cyclohexane, ethanol + dimethylformamide + cyclohexane, dimethylformamide + tetrahydrofuran + cyclohexane). A peculiar behaviour was observed for mixtures containing dimethylformamide, namely the negative values of both H E and C p E ternary contributions. A satisfactory prediction of experimental H E data is provided by the UNIQUAC model, while UNIFAC (Dortmund, Germany) clearly fails probably owing to an unsufficient definition of interaction parameters involving dimethylformamide.

Excess enthalpies and excess heat capacities at 298.15 K for the ternary system ethanol + dimethylformamide + cyclohexane, and for the related binary mixtures dimethylformamide + ethanol or cyclohexane were determined by means of a flow calorimetric apparatus built in our laboratory. Experimental data were described with a Redlich-Kister type equation. H E and C P E data are positive in the whole region of miscibility; however, their ternary contributions to the excess quantities, referred to the combination of the Redlich-Kister representation of the parent binary mixtures, present opposite features. UNIQUAC and UNIFAC models were used for the description or prediction of experimental results.

By means of a vibrating-tube densimeter, the densities at 25°C have been determined for binary mixtures of tetrachloromethane with a liquid (cyclodecane, cis-decahydronaphthalene, trans-decahydronaphthalene, bicyclohexyl, pentane) or a solid hydrocarbon (cyclododecane, cyclopentadecane, norbornane, adamantane, octahydro-4,7-methano-1H-indene). Excess molar volumes have been obtained in the whole mole fraction range for mixtures containing a liquid hydrocarbon. For solid cycloalkanes, apparent molar volumes have been evaluated in the whole range of miscibility. The partial molar volumes at infinite dilution\(\bar V^\circ \) have been calculated for all examined cycloalkanes and compared with those of n-alkanes. The dependence of\(\bar V^\circ \) upon the size and shape of the ring or cage structure of the solute is discussed. The capability of the Flory theory to reproduce VE for these mixtures is also tested.

Spanedda, A., Lepori, L. and Matteoli, E., 1991. Volumes of mixing of ethers with tetrachloromethane at 298.15 K. Fluid Phase Equilibria , 69: 209-222. The excess molar volumes V E , at 298.15 K, have been determined by means of a vibrating-tube densimeter in the whole mole fraction range for binary mixtures of tetra-chloromethane with an ether (diethyl ether, dimethoxymethane, diethoxymethane, 1,2-di-methoxyethane, 1,2-diethoxyethane, diethyleneglycol dimethyl ether, oxepane or 1,3-dioxolane). The V E values are negative for all systems and become less negative with increasing number of oxygen atoms in the ether molecule. The V E values of some of the present mixtures have been analyzed in terms of the Flory theory of non-polar solutions. Limiting partial molar volumes − V o have been evaluated for each component of the examined systems. The behaviour of − V o of ethers is discussed and a simple group additivity scheme is presented.

Vapor-liquid equilibria for dichloromethane or chlorobutane+a linear mono-, or diether (diethyl ether, dipropyl ether, methyl butyl ether, 1,2-dimethoxyethane,) or an acetal (diethoxymethane), were determined at 25°C by head-space gas chromatographic analysis of the vapor phase directly withdrawn from an equilibration apparatus. Excess Gibbs energies, G E , activity coefficients at infinite dilution, f i o as well as free energy of solvation, ΔG o , were evaluated for all the systems. A tentative approach is presented based either on an additivity scheme of surface interactions and scaled particle theory to calculate group contribution to the free energy of solvation.

A head-space gas chromatographic technique has been used to determine vapour—liquid equilibria for binary mixtures of: cyclohexane+an aldehyde (ethanal, butanal, pentanal); tetrachloromethane+ethanal, +pentanal and +cyclobutanone; and heptane+cyclobutanone or+a diketone (2,3-butanedione, 2,5-hexanedione). Excess molar Gibbs energies, GE, for the mixtures investigated were obtained by a least-squares treatment of the equilibrium results. All systems exhibit positive deviations. For mixtures involving aldehydes, the GE values are larger when the other component is cyclohexane than when it is tetrachloromethane and decrease with increasing aldehyde chain length. Activity coefficients at infinite dilution, f∞, as well as free energies of solvation, δG°, were evaluated for each component of the systems examined. A tentative approach, based on an additivity scheme of surface interactions combined with the Scaled Particle Theory, is presented to estimate and to analyse group contributions to δG°.

Marongiu, B., Pittau, B., Porcedda, S., and Tine, M.R., 1994. Thermodynamics of binary mixtures containing linear or cyclic alkenes + n -alkanes or cyclohexane. Fluid Phase Equilibria 93; 249-276. A head-space technique has been used to determine vapor-phase equilibria for binary mixtures of linear or cyclic mono- and polyalkenes + n-alkanes or + cyclohexane. Excess molar Gibbs energies GE for the mixtures investigated were obtained by a least-squares treatment of the equilibrium results. These data the previously measured excess enthalpies HE and the data available in the literature on GE HE activity coefficients at infinite dilution γi∞ and molar excess enthalpies at infinite dilution hiE,∞ are examined on the basis of the DISQUAC group contribution model. The model provides a fairly consistent description of the phase equilibria and the related excess functions using a unique set of structure-dependent dispersive parameters.

The activity coefficiens, γi, and the partial molal volumes, Vi, of the three components of the ternary system water(1)+1-propanol(2)+urea(3) have been measured at 298.15 K in the entire domain of full miscibility. These data have been used to calculate the six Kirkwood-Buff (K-B) integrals, Gij, of the ternary mixture. γ1 and γ2 are found very little dependent on urea mole fraction x3. indicating the scarce influence of urea on the interaction free energy between water and propanol. V1 and V2 too are little dependent on urea concentration; V2 shows a characteristic minimum in dilute alcohol solution even at high x3 values. The increase of V3 with x3, a characteristic of hydrophilic compounds in water, is found even at high x2. The observed increase of the three homologous Gii's and of G12 and the decrease of G23 and G12 with addition of urea indicate that this compound brings about an enhanced homocoordination of the three components, as well as an increase of the urea-water affinity, and suggest that the observed increase of G22 with urea addition may be due to the abduction of water molecules from the solvation sphere of propanol.

The apparent molar heat capacities, Cp,ϕ, of alkaline aqueous solutions of aluminum ion in excess NaOH have been measured at temperatures between 50 and 250°C in the overall molality range 0.3–1.7 mol-kg−1. Enthalpies of dilution, ΔLϕ, have also been determined at 99°C and apparent molar relative enthalpies, Lϕ, were calculated starting from 2.16 mol-kg−1 as the maximum concentration. Measurements of the above quantities have been performed by means of a differential flow calorimeter built in our laboratory and already described. The thermodynamic data obtained and the corresponding quantities for aqueous NaOH previously determined have been fitted to the equations of the Pitzer ionic interaction model to obtain parameters relative to aqueous NaAl(OH)4. These parameters permit the calculation of Cp,ϕ, and Lϕ for this species over the examined range of temperatures and concentrations.

The limiting apparent molal adiabatic and isothermal compressibilities in aqueous solutions of alcohols and ethers at various temperatures have been determined by means of ultrasonic velocity measurements. The following compounds have been considered: secondary cyclic and open-chain alcohols (cyclopentanol, cyclohexanol, cycloheptanol, 2-butanol, 3-pentanol, 3-hexanol, 4-heptanol; cyclic ethers of the types (CH2)3On (n=1, 2, 3), (CH2)nO2 (n=3, 4, 5), and (CH2)nO (n=3, 4, 5); and the linear diethers dimethoxymethane, diethoxymethane, and 1,2-dimethoxyethane. The results indicate that both alcohols and ethers cause the water near the solute to become more resistant to pressure than the bulk. This is in agreement with the prediction of a mixture model for water.

The apparent molar heat capacity, C p,ϕ, of aqueous NaOH has been measured at temperatures between 50 and 250°C and molalities from 0.05 to 1.5 mol-kg−1. Enthalpies of dilution ΔLϕ were also determined at 99°C and apparent molar relative enthalpies Lϕ were calculated up to 1.9 m. Measurements were performed by means of a flow calorimetric apparatus constructed in our laboratory and standardized for C p,ϕ and ΔLϕ with aqueous Na2SO4 and with the formation of water from its ions, respectively. Characteristics and performance of this calorimeter are described in detail. Pitzer's semiempirical equations are used for the representation of the results and a general fitting of C p,ϕ data is reported using also recent literature values measured between 4 and 55°C. The fitted parameters are finally utilized, through an integration procedure, to derive a general equation to calculate Lϕ at any temperature between 4 and 250°C.

The temperature dependence of limiting apparent molal volumes Φ°υ in water for some alcohols (methanol, ethanol, 1-propanol, 2-butanol, 3-pentanol, 3-hexanol, 2,5-hexanediol, cyclopentanol, cyclohexanol, cycloheptanol, and 1,4-cyclohexanediol) and ethers (trimethylene oxide, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxepane, 1,3,5-trioxane, dimethoxymethane, 1,2-dimethoxyethane, diethoxymethane, and diethyl ether) has been studied in the temperature range 10–50°C by means of an automatic digital-readout dilatometer. Values of the thermal expansion coefficient α* = (1/Φ°υ)(∂Φ°υ/∂T)p have been obtained at several temperatures and discussed together with literature data on expansibilities of related compounds. The data show a wide spectrum of values of α* at low temperatures which is narrowed at the higher ones. The expansibilities of monofunctional alcohols increase with increasing temperature; the opposite effect is observed for polyhydric alcohols. The α*'s of ethers are very slightly temperature dependent and are much higher, at low temperature, than those of alcohols having the same ratio ofno/nc. These results are discussed in terms of solutewater interactions, and a possible interpretation is put forward.

Apparent molal heat capacities of 20 organic uncharged compounds in aqueous solution have been determined at 25 and 40°C. The substances studied include mono- and polyfunctional ethers, and bifunctional open-chain compounds like aminoalcohols, aminoethers, and diamines. The results obtained support the presence of interaction between water and the hydrophilic groups −O−, −NH2, −NH−, and\(\begin{array}{*{20}c} \backslash \\ / \\ \end{array} N - \), and evidence indicates that these interactions strongly depend on the molecular structure of the compound containing the functional group.