Apparent molar heat capacities and apparent molar volumes of Pr(ClO4)3(aq), Gd(ClO4)3(aq), Ho(ClO4)3(aq), and Tm(ClO4)3(aq) at T=(288.15, 298.15, 313.15, and 328.15) K and p=0.1 MPa

Acidified aqueous solutions of Pr(ClO₄)₃(aq), Gd(ClO₄)₃(aq), Ho(ClO₄)₃(aq), and Tm(ClO₄)₃(aq) were prepared from the corresponding oxides by dissolution in dilute perchloric acid. Once characterized with respect to trivalent metal cation and acid content, the relative densities of the solutions were measured at T=(288.15, 298.15, 313.15, and 328.15) K and p=0.1 MPa using a Sodev O2D vibrating tube densimeter. The relative massic heat capacities of the aqueous systems were also determined, under the same temperature and pressure conditions, using a Picker Flow Microcalorimeter. All measurements were made on solutions containing rare earth salt in the concentration range 0.01 ⩽ m/(mol · kg⁻¹) ⩽ 0.2. Relative densities and relative massic heat capacities were used to calculate the apparent molar volumes and apparent molar heat capacities of the acidified salt solutions from which the apparent molar properties of the aqueous salt solutions were extracted by the application of Young's Rule. The concentration dependences of the isothermal apparent molar volumes and heat capacities of each aqueous salt solution were modelled using Pitzer ion-interaction equations. These models produced estimates of apparent molar volumes and apparent molar heat capacities at infinite dilution for each set of isothermal V_φ,2 and C_pφ,2 values. In addition, the temperature and concentration dependences of the apparent molar volumes and apparent molar heat capacities of the aqueous rare earth perchlorate salt solutions were modelled using modified Pitzer ion-interaction equations. The latter equations utilized the Helgeson, Kirkham, and Flowers equations of state to model the temperature dependences (at p=0.1 MPa) of apparent molar volumes and apparent molar heat capacities at infinite dilution. The results of the latter models were compared to those previously published in the literature.Apparent molar volumes and apparent heat capacities at infinite dilution for the trivalent metal cations Pr³⁺(aq), Gd³⁺(aq), Ho³⁺(aq), and Tm³⁺(aq) were calculated using the conventions V₂^∘(H⁺(aq)) ≡ 0 and C_p2^∘(H⁺(aq)) ≡ 0 and have been compared to other values reported in the literature.     

Thermodynamics of Selected Aqueous Rare-Earth Elements Containing Triflate Salts at T=(288.15, 298.15, 313.15 and 328.15) K and p=0.1 MPa

Aqueous acidified solutions of the rare-earth-element (REE) triflates (Gd(CF₃SO₃)_3(aq), Dy(CF₃SO₃)_3(aq), Nd(CF₃SO₃)_3(aq), Er(CF₃SO₃)_3(aq), Yb(CF₃SO₃)_3(aq) and Y(CF₃SO₃)_3(aq)) have been prepared by the dissolution of the corresponding REE oxides in dilute aqueous trifluoromethanesulfonic acid (triflic acid, CF₃SO₃H_(aq)). Relative densities and relative massic heat capacities have been measured for these systems over the approximate ionic strength range 0.10≤I/(mol?kg^?1)≤1.35 at T=(288.15, 298.15, 313.15 and 328.15) K and p=0.1 MPa. These measurements were completed using a Sodev O2D vibrating tube densimeter and Picker-flow microcalorimeter, respectively. Relative densities and relative massic heat capacities for aqueous solutions of triflic acid and its sodium salt have also been measured over the concentration range 0.018≤m ₂/(mol?kg^?1)≤0.23 over the same temperature range at p=0.1 MPa. Young’s rule has been used to calculate apparent molar volumes and apparent molar heat capacities of the aqueous solutions of REE triflate salts from the calculated apparent molar properties of the acidified salt solutions. These properties have been modeled using the Pitzer ion-interaction equations. The apparent molar properties of aqueous triflic acid solutions and aqueous solutions of its sodium salt have also been modeled using the same Pitzer ion-interaction equations. The apparent molar properties at infinite dilution obtained from our property modeling have been used to calculate single ion volumes and single ion heat capacities for each of the aqueous ions; Gd _(aq) ³⁺ , Dy _(aq) ³⁺ , Nd _(aq) ³⁺ , Er _(aq) ³⁺ , Yb _(aq) ³⁺ , and Y _(aq) ³⁺ . The reported single ion values have been compared with those previously reported in the literature.     

Apparent molar heat capacities and apparent molar volumes ofY2(SO4)3(aq),La2(SO4)3(aq),Pr2(SO4)3(aq),Nd2(SO4)3(aq),Eu2(SO4)3(aq),Dy2(SO4)3(aq),Ho2(SO4)3(aq), andLu2(SO4)3(aq)atT = 298.15 K andp = 0.1 MPa

The apparent molar heat capacities C_{p, φ} ^∘ and apparent molar volumes V_φ ^∘ of Y₂(SO₄)₃(aq), La₂(SO₄)₃(aq), Pr₂(SO₄)₃(aq), Nd₂(SO₄)₃(aq), Eu₂(SO₄)₃(aq), Dy₂(SO₄)₃(aq), Ho₂(SO₄)₃(aq), and Lu₂(SO₄)₃(aq) were measured at T =  298.15 K and p =  0.1 MPa with a Sodev (Picker) flow microcalorimeter and a Sodev vibrating-tube densimeter, respectively. These measurements extend from lower molalities of m =  (0.005 to 0.018) mol ·kg ^− 1to m =  (0.025 to 0.434) mol ·kg ^− 1, where the upper molality limits are slightly below those of the saturated solutions. There are no previously published apparent molar heat capacities for these systems, and only limited apparent molar volume information. Considerable amounts of the R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are present, where R denotes a rare-earth, which complicates the interpretation of these thermodynamic quantities. Values of the ionic molar heat capacities and ionic molar volumes of these complexes at infinite dilution are derived from the experimental information, but the calculations are necessarily quite approximate because of the need to estimate ionic activity coefficients and other thermodynamic quantities. Nevertheless, the derived standard ionic molar properties for the various R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are probably realistic approximations to the actual values. Comparisons indicate that V_φ ^∘ {RSO₄ ⁺ , aq, 298.15K}  =  − (6  ±  4)cm³· mol ^− 1and V_φ ^∘ {R(SO₄)₂ ⁻ , aq, 298.15K}  =  (35  ±  3)cm³· mol ^− 1, with no significant variation with rare-earth. In contrast, values of C_{p, φ} ^∘ { RSO₄ ⁺ , aq, 298.15K } generally increase with the atomic number of the rare-earth, whereas C_{p, φ} ^∘ { R(SO₄)₂ ⁻ , aq, 298.15K } shows a less regular trend, although its values are always positive and tend to be larger for the heavier than for the light rare earths.     

Sublimation enthalpy of Ni(II) and Cu(II) diethyldithiocarbamate and diethylammonium diethyldithiocarbamate by the sublimation bulb technique

We have used a flow calorimeter and a flow densimeter for measurements leading to apparent molar heat capacities and apparent molar volumes of dilute aqueous solutions of NaIO₃, KMnO₄, and MnCl₂ at 25°C. These apparent molar quantities have been extrapolated to infinite dilution to obtain the corresponding standard state apparent and partial molar heat capacities and volumes. which have then been used for the calculation of conventional ionic heat capacities and volumes.     

The Calorimetric and Volumetric Properties of Selected α-Amino Acids and α,ω-Amino Acids in Water at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa

Relative densities and relative massic heat capacities have been measured for the amino acids β-alanine, 4-aminobutanoic acid, d,l-norleucine and d,l-norvaline in dilute aqueous solution at p = 0.1 MPa and T = (288.15, 298.15, 313.15 and 328.15) K. Apparent molar volumes and apparent molar heat capacities have been calculated and the isothermal concentration dependences of these properties have been modeled to yield apparent molar properties at infinite dilution. Values for apparent molar properties at infinite dilution are compared to those previously reported in the literature. Trends in the temperature dependences of the infinite dilution properties are discussed in terms of methylene group contributions and the variations in these contributions caused by the presence of ionic end groups.     

Apparent molar heat capacities and volumes of aqueous electrolytes at 25°C: Cd(ClO4)2, Ca(ClO4)2, Co(ClO4)2, Mn(ClO4)2, Ni(ClO4)2, and Zn(ClO4)2

We have used a flow calorimeter and a flow densimeter for measurements leading to apparent molar heat capacities and apparent molar volumes of aqueous solutions of Cd(ClO₄)₂, Ca(ClO₄)₂, Co(ClO₄)₂, Mn(ClO₄)₂, Ni(ClO₄)₂, and Zn(ClO₄)₂. The resulting apparent molar quantities have been extrapolated to infinite dilution to obtain the corresponding standardstate apparent and partial molar heat capacities and volumes. These latter values have been used for calculation of conventional ionic heat capacities and volumes.     

Thermodynamics of aqueous phosphate solutions: Apparent molar heat capacities and volumes of the sodium and tetramethylammonium salts at 25°C

A Picker flow microcalorimeter and a flow densimeter were used to obtain apparent molar heat capacities and apparent molar volumes of aqueous solutions of Na₃PO₄ and mixtures of Na₂HPO₄ and NaH₂PO₄. Identical measurements were also made on solutions of tetramethylammonium salts to evaluate the importance of anion-cation interaction. The experimental apparent molar properties were analyzed in terms of a simple extended Debye-Hückel model and the Pitzer ion-interaction model, both with a suitable treatment for the effect of chemical relaxation on heat capacities, to derive the partial molar properties of H₂PO ₄ ^– (aq), HPO ₄ ^2– (aq) and PO ₄ ^3– (aq) at infinite dilution. The volume and heat capacity changes for the second and third ionization of H₃PO₄(aq) have been determined from the experimental data. The importance of ionic complexation with sodium is discussed.     

Apparent molar heat capacities and volumes of aqueous electrolytes: CaCl2, Cd(NO3)2, CoCl2, Cu(ClO4)2, Mg(ClO4)2, and NiCl2

We have used a flow calorimeter and a flow densimeter for measurements leading to apparent molar heat capacities and apparent molar volumes of six 21 electrolytes in aqueous solution at 25°C. Results of these measurements have been used to derive apparent molar heat capacities and volumes at infinite dilution for all six electrolytes: CaCl₂, Cd(NO₃)₂, CoCl₂, Cu(ClO₄)₂, Mg(ClO₄)₂, and NiCl₂.     

Thermodynamics of Aqueous Diethylenetriaminepentaacetic Acid (DTPA) Systems: Apparent and Partial Molar Heat Capacities and Volumes of Aqueous H2DTPA3−, DTPA5−, CuDTPA3−, and Cu2DTPA− from 10 to 55°C

Apparent molar heat capacities and volumes have been determined for aqueous solutions of the mixed electrolytes Na₅DTPA + NaOH, Na₃CuDTPA + NaOH, and NaCu₂DTPA + NaOH, and the single electrolyte Na₃H₂DTPA (DTPA=diethylenetriaminepentaacetic acid) at temperatures from 10 to 55°C. The experimental results have been analyzed in terms of Young's rule with the Guggenheim form of the extended Debye–Hückel equation and the Pitzer ion-interaction model. These calculations led to standard partial molar heat capacities and volumes for the species H₂DTPA^3–(aq), DTPA^5–(aq), CuDTPA^3–(aq), and Cu₂DTPA^–(aq) at each temperature. The partial molar properties at 0.1 m ionic strength were also calculated. The standard partial molar properties were extrapolated to elevated temperatures with the revised Helgeson–Kirkham–Flowers (HKF) model. Values for the partial molar heat capacities from the HKF model have been combined with the literature data to estimate the ionization constants of H₂DTPA^3–(aq) and the formation constant of the CuDTPA^3–(aq) copper complex at temperatures up to 300°C.     

Apparent molar heat capacities of aqueous solutions of phosphoric acid and sulfur dioxide from 303 to 623 K and a pressure of 28 MPa

Heat capacities of aqueous solutions of phosphoric acid from 0.1 to 0.8 mol- kg^-1 and sulfur dioxide from 0.2 to 0.9 mol-kg^-1 have been measured with a flow heat-capacity calorimeter from 303 to 623 K and a pressure of 28 MPa. At the lowest molality single-solute solutions as well as mixtures of either H₃PO₄ or SO₂ with HC1 were measured to repress dissociation. Calculated apparent molar heat capacities were corrected for dissociation reactions and the chemical relaxation effect. Experimental results for mixtures were analyzed using Young’s rule. Standard state partial molar heat capacities of H₃PO₄(aq) and SO₂(aq) were obtained by extrapolation to infinite dilution. A few measurements of the densities of aqueous H₃PO₄ and SO₂ were made at 25°C and a pressure of 28 MPa.     

Standard thermodynamic properties of H3PO4(aq) over a wide range of temperatures and pressures

The densities and heat capacities of solutions of phosphoric acid, 0.05 to 1 mol kg-1, were measured using flow vibrating tube densitometry and differential Picker-type calorimetry at temperatures up to 623 K and at pressures up to 28 MPa. The standard molar volumes and heat capacities of molecular H3PO4(aq) were obtained, via the apparent molar properties corrected for partial dissociation, by extrapolation to infinite dilution. The data on standard derivative properties were correlated simultaneously with the dissociation constants of phosphoric acid from the literature using the theoretically founded SOCW model. This made it possible to describe the standard thermodynamic properties, particularly the standard chemical potential, of both molecular and ionized phosphoric acid at temperatures up to at least 623 K and at pressures up to 200 MPa. This representation allows one to easily calculate the first-degree dissociation constant of H3PO4(aq). The performance of the SOCW model was compared with the other approaches for calculating the high-temperature dissociation constant of the phosphoric acid. Using the standard derivative properties, sensitively reflecting the interactions between the solute and the solvent, the high-temperature behavior of H3PO4(aq) is compared with that of other weak acids.     

Densities and Apparent Molar Volumes of NaOH(aq) to the Temperature 623 K and Pressure to 30 MPa

Densities of NaOH(aq) solutions with molalities between 0.033 and 6.047 mol⋅kg⁻¹ were measured with a vibrating-tube densitometer at temperatures between 373 K and 623 K and pressures from near the saturation vapor pressure of water to 30 MPa. Apparent molar volumes, V _φ, calculated from the measured densities in this work were well represented with the Pitzer ion-interaction treatment up to T = 523 K. Above that temperature the formation of ion pairs must be taken into account to describe correctly the molality dependence of V _φ and for the reliable extrapolation of V _φ to infinite dilution. Standard-state thermodynamic properties for the ion formation reaction were taken from recently published electrical conductivity measurements. A comparison with previous correlations of volumetric properties of NaOH(aq) is presented covering the full range of pressure and temperature.     

Partial molar volumes of organic solutes in water. XII. Methanol(aq), ethanol(aq), 1-propanol(aq), and 2-propanol(aq) at T = (298 to 573) K and at pressures up to 30 MPa

Density data for dilute aqueous solutions of methanol, ethanol, 1-propanol, and 2-propanol are presented together with partial molar volumes at infinite dilution calculated from the experimental data. The measurements were performed at from T = (298.15 up to 573.15) K and at pressure close to the saturated vapor pressure of water, at p = 30 MPa and at pressure between these limits. The data were obtained using a high-temperature high-pressure flow vibrating-tube densimeter.     

Volumetric properties of ascorbic acid (vitamin C) and thiamine hydrochloride (vitamin B1) in dilute HCl and in aqueous NaCl solutions at (283.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K

Apparent molar volumes and apparent molar isentropic compressibilities of ascorbic acid (vitamin C) and thiamine hydrochloride (vitamin B₁) were determined from accurately measured density and sound velocity data in water and in aqueous NaCl solutions at (283.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K. These volume and compressibility data were extrapolated to zero concentration using suitable empirical or theoretical equations to determine the corresponding infinite dilution values. Apparent molar expansibilities at infinite dilution were determined from slopes of apparent molar volume vs. temperature plots. Ionization of both ascorbic acid and thiamine hydrochloride were suppressed using sufficiently acidic solutions. Apparent molar volumes at infinite dilution for ascorbic acid and thiamine hydrochloride were found to increase with temperature in acidic solutions and in the presence of co-solute, NaCl. Apparent molar expansibility at infinite dilution were found to be constant over the temperature range studied and were all positive, indicating the hydrophilic character of the two vitamins studied in water and in the presence of co-solute, NaCl. Apparent molar isentropic compressibilities of ascorbic acid at infinite dilution were positive in water and in the presence of co-solute, NaCl, at low molalities. Those of thiamine hydrochloride at infinitive dilution were all negative, consistent with its ionic nature. Transfer apparent molar volumes of vitamins at infinite dilution from water solutions to NaCl solutions at various temperatures were determined. The results were interpreted in terms of complex vitamin-water-co-solute (NaCl) interactions.     

Effect of alkyl chain length and temperature on the thermodynamic properties of ionic liquids 1-alkyl-3-methylimidazolium bromide in aqueous and non-aqueous solutions at different temperatures

The alkyl chain length of 1-alkyl-3-methylimidazolium bromide ([Rmim][Br], R = propyl (C₃), hexyl (C₆), heptyl (C₇), and octyl (C₈)) was varied to prepare a series of room-temperature ionic liquids (RTILs), and experimental measurements of density and speed of sound at different temperatures ranging from (288.15 to 308.15) K for their aqueous and methanolic solutions in the dilute concentration region (0.01 to 0.30) mol · kg^?1 were taken. The values of the compressibilities, expansivity and apparent molar properties for [C_nmim][Br] in aqueous and methanolic solutions were determined at the investigated temperatures. The obtained apparent molar volumes and apparent molar isentropic compressibilities were fitted to the Redlich–Mayer and the Pitzer’s equations from which the corresponding infinite dilution molar properties were obtained. The values of the infinite dilution molar properties were used to obtain some information about solute–solvent and solute–solute interactions. The thermodynamic properties of investigated ionic liquids in aqueous solutions have been compared with those in methanolic solutions. Also, the comparison between thermodynamic properties of investigated solutions and those of electrolyte solutions, polymer solutions, cationic surfactant solutions and tetraalkylammonium salt solutions have been made.     

Isopiestic Determination of the Osmotic and Activity Coefficients of Li2SO4(aq) at T=298.15 and 323.15 K, and Representation with an Extended Ion-Interaction (Pitzer) Model

Isopiestic vapor-pressure measurements were made for Li₂SO₄(aq) from 0.1069 to 2.8190 mol?kg^?1 at 298.15 K, and from 0.1148 to 2.7969 mol?kg^?1 at 323.15 K, with NaCl(aq) as the reference standard. Published thermodynamic data for this system were reviewed, recalculated for consistency, and critically assessed. The present results and the more reliable published results were used to evaluate the parameters of an extended version of Pitzer’s ion-interaction model with an ionic-strength dependent third-virial coefficient, as well as those of the standard Pitzer model, for the osmotic and activity coefficients at both temperatures. Published enthalpies of dilution at 298.15 K were also analyzed to yield the parameters of the ion-interaction models for the relative apparent molar enthalpies of dilution. The resulting models at 298.15 K are valid to the saturated solution molality of the thermodynamically stable phase Li₂SO₄?H₂O(cr). Solubilities of Li₂SO₄?H₂O(cr) at 298.15 K were assessed and the selected value of m(sat.)=3.13±0.04 mol?kg^?1 was used to evaluate the thermodynamic solubility product K _s(Li₂SO₄?H₂O, cr, 298.15 K) = (2.62±0.19) and a CODATA-compatible standard molar Gibbs energy of formation Δ_f G _m ^o (Li₂SO₄?H₂O, cr, 298.15 K) = ?(1564.6±0.5) kJ?mol^?1.     

Thermodynamics of Aqueous Nitrilotriacetic Acid (NTA) Systems: Apparent and Partial Molar Heat Capacities and Volumes of Aqueous HNTA2−, NTA3−, MgNTA−, CoNTA−, NiNTA− and CuNTA− at 25 °C

Apparent molar heat capacities and volumes have been determined for aqueous Na₂HNTA, Na₃NTA, NaMgNTA, NaCoNTA, NaNiNTA and NaCuNTA at 25 °C. The experimental results have been analyzed in terms of Young’s rule with an extended Debye–Hückel equation to obtain standard partial molar heat capacities C _p ^o and volumes V ^o for the species HNTA²⁻(aq), NTA³⁻(aq), MgNTA⁻(aq), CoNTA⁻(aq), NiNTA⁻(aq) and CuNTA⁻(aq), at ionic strengths I = 0 and I = 0.1 mol⋅kg⁻¹. Values of C _p ^o and V ^o were combined with the literature data to estimate the stability constants of the NTA complexes at temperatures up to 100 °C.     

Aqueous Guanidinium Salts: Part I. Densities, Ultrasonic Velocities, and Apparent Molar Properties

The densities and ultrasonic velocities in aqueous solutions of guanidinium chloride, bromide, acetate, perchlorate and sulfate have been measured at 25°C. The infinite dilution partial molar volumes and compressibilities of the salts were estimated and analyzed by the Pitzer equations. The concentration dependence of densities and sound velocities of the guanidinium salts can be correlated by the Pitzer equations with an average root-mean-square deviation of 0.025 kg-m^-3 and 0.31 m-s^-1, respectively.     

The apparent molar heat capacities and volumes of aqueous NaCl from 0.01 to 3 mol kg−1 in the temperature range 274.65 to 318.15 K

The heat capacities per unit volume of aqueous solutions of NaCl were measured with a flow microcalorimeter. The molality and temperature range covered were 0.01 to 3 mol kg^?1 and 274.65 to 318.15 K. The derived apparent molar heat capacities C₂, φ, when extrapolated to infinite dilution, give standard partial molar heat capacities C₂^o which are in excellent agreement with those of Criss and Cobble. The excess apparent molar heat capacities (C₂, φ - C₂^o) can be used to predict the temperature dependence of (H₂, φ - H₂^o), the excess apparent molar enthalpy. The calculated values of ΔH₂, φ agree within experimental uncertainty with the integral enthalpies of dilution of Ensor and Anderson and of Messikomer and Wood up to 323.15 K. Above this temperature significant differences are observed. The densities of the solutions were also remeasured in the same range of temperature and molality with a flow densimeter, and the derived apparent molar volumes agree with the literature values.