Thermodynamics of binary liquid mixtures of cyclopentane with 2-propanol, 1-butanol and 2-butanol at different temperatures

Densities and speeds of sound of the cyclopentane with 2-propanol, 1-butanol and 2-butanol are measured over the whole composition range at different temperatures in the range 288.15–308.15 K and atmospheric pressure using Anton Paar DSA 5000 densimeter. The experimental densities and speeds of sound have been used to calculate excess molar volumes, excess molar isentropic compressibilities and excess intermolecular free length. The partial molar volumes and apparent molar volumes at infinite dilution have also been calculated. The mixing quantities like (∂V _m^E/∂T)_P and (∂H _m^E/∂P)_T have been calculated at T = 298.15 K and these values are compared with the values calculated from Flory’s theory at equimolar composition.     

Heat capacities and thermodynamic properties of 2-benzoylpyridine (C12H9NO)

The heat capacities of 2-benzoylpyridine were measured with an automated adiabatic calorimeter over the temperature range from 80 to 340 K. The melting point, molar enthalpy, Δ_fusH^m, and entropy, Δ_fusS^m, of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03 kJ mol^–1 and 66.07±0.05 J mol^–1 K^–1, respectively. The purity of the compound was calculated to be 99.60 mol% by using the fractional melting technique. The thermodynamic functions (H_T–H_298.15) and (S_T–S_298.15) were calculated based on the heat capacity measurements in the temperature range of 80–340 K with an interval of 5 K. The thermal properties of the compound were further investigated by differential scanning calorimetry (DSC). From the DSC curve, the temperature corresponding to the maximum evaporation rate, the molar enthalpy and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2 kJ mol^–1 and 92.2±0.4 J K^–1 mol^–1, respectively, under the experimental conditions.     

Different coordination modes of the dimethyldisulfide ligand in trimethylplatinum(IV) complexes

The reaction of [PtMe₃(bpy)(Me₂CO)](BF₄) (2) (prepared from [PtMe₃I(bpy)] (1) plus Ag(BF₄)) with MeSSMe resulted in the formation of [PtMe₃(bpy)(MeSSMe-κS)](BF₄) (3). A single-crystal X-ray diffraction analysis revealed in the octahedral Pt(IV) complex (configuration index: OC-6-33), a conformation of the monodentately κS bound MeSSMe ligand (C–S–S–C 92.7(4)°) being very close to that in non-coordinated MeSSMe, thus allowing some hyperconjugative interaction stabilizing the S–S bond. The reaction of [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (4; 18C6 = 18-crown-6, Hpz = pyrazole) with Ag(BF₄) and MeSSMe resulted in the formation of dinuclear complexes [(PtMe₃)₂(μ-pz)₂(μ-MeSSMe)] existing at room temperature in acetone solution as different fast interconverting isomers. At –40 °C, two isomers with a μ-1κS:2κS (5a) and a μ-1κS:2κS′ (5b) coordinated MeSSMe ligand in the ratio 2:1 could be identified ¹H NMR spectroscopically. DFT calculations of type 5 complexes revealed the existence of two conformers with a μ-MeSSMe-1κS:2κS ligand, which differ mainly in the C–S–S–C dihedral angle (66.4 vs. 180.0° 6a/6a′). They have essentially the same energy and a very low activation barrier in acetone as solvent (1.3 kcal/mol) for their mutual interconversion. A further equilibrium structure was identified to be an isomer having a μ-MeSSMe-1κS:2κS′ ligand (6b) that proved to be only 1.9 kcal/mol higher in energy than 6a/6a′.     

Ultrasound Speeds and Molar Isentropic Compressions of Aqueous Binary Mixtures of Diethylamine from 278.15 to 308.15 K

Ultrasound speeds in aqueous binary mixtures of diethylamine (DEA) were measured across the entire composition range at five temperatures between 278.15 and 308.15 K. Isentropic compressibilities, κ _S , were calculated from the ultrasound speed and density data. The excess molar isentropic compressions, K _S,m ^E, were estimated and their variation with the mole fraction of the amine were fitted by the Redlich–Kister equation. Excess partial molar isentropic compressions, K _S,i ^E, were then obtained, allowing separation of the role of each component in the mixing process. Interesting insights are gained from the analysis of the temperature and composition dependence of K _S,i ^E, principally in the water-rich region. A comparison of the limiting values of this property with those of the limiting excess partial molar isobaric expansion, E _P,i ^E,∞, previously published, clearly shows the different sensitivity of these two differential thermodynamic properties to the mixing process. The different behavior of the temperature dependence of K _S,i ^E,∞ in the systems, water + DEA, and water + 2-diethylaminoethanol (DEEA), are also analyzed and interpreted in terms of changes in the solute configuration, the degree of hydrolysis and solute-solvent interactions.     

Heat capacity and heat content of BiNb<Subscript>5</Subscript>O<Subscript>14</Subscript>

The heat capacity and the heat content of bismuth niobate BiNb₅O₁₄ were measured by the relaxation time method, DSC and drop method, respectively. The temperature dependence of heat capacity in the form C _pm=455.84+0.06016T–7.7342·10⁶/T ² (J K^–1 mol^–1) was derived by the least squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S _m=397.17 J K^–1 mol^–1 was derived from the low temperature heat capacity measurement.     

Volumetric and Ultrasonic Investigation of Glycylglycine in Aqueous FeCl<Subscript>3</Subscript> Solutions

Viscosity, ultrasonic velocity and density measurements have been carried out for glycylglycine in aqueous FeCl₃ solution as a function of molality at T=288.15 K, 298.15 K and 308.15 K. The experimental data have been used to derive properties such as isentropic compressibility (κ _S ), change in isentropic compressibility (Δκ _S ), relative change in isentropic compressibility (Δκ _S /κ ₀), apparent molar compressibility, volume and their limiting apparent molar quantities along with the constants S _K , S _V and viscosity B-coefficient. The obtained thermodynamic properties have been discussed in terms of molecular interactions.     

Acoustical Studies of Binary Liquid Mixtures of Cyclopentane with 1-Alkanol at Different Temperatures and Different Approaches for Ideal Mixing Laws

Speeds of sound have been measured in liquid mixtures of cyclopentane with 1-propanol, with 1-pentanol, and with 1-heptanol across the entire composition range at temperatures of (298.15, 308.15 and 318.15) K and atmospheric pressure. The experimental speed of sound data were used to estimate the isentropic compressibility κ _S for all mixtures. The molar volumes were multiplied by the corresponding isentropic compressibilities to obtain estimates of the molar compressibilities K _S,m. The corresponding K_S,m^EK_{S,\mathrm{m}}^{\mathrm{E}} values have also been calculated. Theoretical values of the speeds of sound were estimated using theories and empirical relations. Deviations of the speed of sound, u ^D, from the values calculated by different approaches for ideal mixing have been obtained for all mole fractions.     

Thermophysical Investigations of the Polymorphous Phases of Calcium Carbonate

1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T _tr=455±10°C, Δ_tr H=403±8 J mol^–1 at T _tr, V→C: T _tr=320–460°C, depending on the way of preparation,Δ_tr H=–3.2±0.1 kJ mol^–1 at T _tr,Δ_tr H=–3.4±0.9 kJ mol^–1 at 40°C, S _V ^Θ= 93.6±0.5 J (K mol)^–1, A→C: E _A=370±10 kJ mol^–1; XRD only, V→C: E _A=250±10 kJ mol^–1; thermally activated, iso- and non-isothermal, XRD 2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are presented. NCC→C: T _tr=276±10°C,Δ_tr H=–15.0±3 kJ mol^–1 at T _tr, T _tr – transition temperature, Δ_tr H – transition enthalpy, S ^Θ – standard entropy, E _A – activation energy. 3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Volumetric properties of 1-iodoperfluorohexane+<Emphasis Type="Italic">n</Emphasis>-octane binary system at several temperatures

New densities are reported over the whole composition range for 1-iodoperfluorohexane+n-octane system at temperatures from 288.15 to 308.15 K at atmospheric pressure. These data have been used to compute the excess molar volumes, V _m ^E. Large positive V _m ^E values have been obtained over the entire range of composition, which increases when the temperature rises. The experimental data were used to calculate the isobaric thermal expansivity, and the quantities (∂V _m ^E/∂T)_p and (∂H _m ^E/∂p)_T. Furthermore, the results have been used to investigate the volumetric prediction ability of the equations of state Soave–Redlich–Kwong, Peng–Robinson, Patel–Teja and Soave–Redlich–Kwong with volume translation.     

Thermodynamics of the Interaction of a Homologous Series of Amino Acids with Sorbitol

The apparent molar volumes V _2,φ , apparent molar isentropic compressibilities K _S,2,φ , and enthalpies of dilution of aqueous glycine, alanine, α-amino butyric acid, valine, and leucine have been determined in aqueous 1.0 and 2.0 mol⋅dm⁻³ sorbitol solutions at 298.15 K. These data have been used to calculate the infinite dilution standard partial molar volumes V_2,m⁰V_{2,m}^{0}, partial molar isentropic compressibilities K_S,2,m⁰K_{S,2,m}^{0}, and enthalpies of dilution Δ_dil H ⁰ of the amino acids in aqueous sorbitol, along with the standard partial molar quantities of transfer of the amino acids from water to aqueous sorbitol. The linear correlation of V_2,m⁰V_{2,m}^{0} for this homologous series of amino acids has been utilized to calculate the contribution to V₂⁰V_{2}^{0} of the charged end groups (NH₃⁺\mathrm{NH}_{3}^{+}, COO⁻), the CH₂ group, and other alkyl chains of the amino acids. The results for the standard partial molar volumes of transfer, compressibilites and enthalpies of dilution from water to aqueous sorbitol solutions have been correlated and interpreted in terms of ion–polar, ion–hydrophobic, and hydrophobic–hydrophobic group interactions. A comparison of these thermodynamic properties of transfer suggest that an enhancement of the hydrophilic/polar group interactions is operating in ternary systems of amino acid, sorbitol, and water.     

Thermal properties of Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–PbO–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glass system

Thermal behavior of xGa₂O₃–(50 − x)PbO–50P₂O₅ (x = 0, 10, 20, and 30 mol.% Ga₂O₃) and xGa₂O₃–(70 − x)PbO–30P₂O₅ (x = 0, 10, 20, 30, and 40 mol.% Ga₂O₃) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of PbO for Ga₂O₃ is accompanied by increasing glass-transition temperature (263 ≤ T _g/°C ≤ 535), deformation temperature (363 ≤ T _d/°C ≤ 672), crystallization temperature (396 ≤ T _c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K⁻¹ ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K _H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga₂O₃.     

Thermodynamic Properties of Peptide Solutions. Part 18. Partial Molar Isentropic Compressibilities of Gly-X-Gly Tripeptides (X = Tyr,Pro, Gln,Asp and Glu), and the Peptide Salts K[GlyAspGly], Na[GlyGluGly] and GlyLysGly Acetate in Aqueous Solution at 25 <Superscript>∘</Superscript>C

The partial molar isentropic compressibilities at infinite dilution, K∘_S,2, have been determined for several tripeptides of the sequence glycyl-X-glycine, where X is one of the amino acids tyrosine, proline, glutamine, aspartic acid, glutamic acid and lysine in aqueous solution at 25 ^∘C. These results, along with those for triglycine, were used to estimate the contributions of the amino acid side-chains to the partial molar isentropic compressibilities of polypeptides. Values for K∘_S,2 have also been determined for aqueous solutions of the two peptide salts K[glyaspgly] and Na[glyglugly]. The K∘_S,2 results for the peptides and their salts have been combined with literature data for electrolytes to calculate the changes in isentropic compressibility upon ionization of the acidic side-chains. The results are compared with those for other carboxylic acid systems.     

Acoustic,Viscometric, and Spectroscopic Studies of Dipropylene Glycol Monopropyl Ether with <Emphasis Type="Italic">n</Emphasis>-Alkanols at Temperatures of 288.15, 298.15, and 308.15 K

Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol, and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds of sound were combined with our previous densitity results to obtain the isentropic compressibility κ _S . The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K _S,m and its excess counterparts K_S,m^EK_{S,m}^{\mathrm{E}}. The K_S,m^EK_{S,m}^{\mathrm{E}} values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑x _i ln η _i and excess Gibbs energies of activation for viscous flow ΔG ^∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities [`(K)]_f,i⁰\overline{K}_{\phi ,i}^{0} of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental results have also been discussed on the basis of IR measurements.     

Apparent molar volume,viscosity, and adiabatic compressibility of some mineral sulfates in aqueous binary mixtures of formamide at 298.15, 308.15, and 318.15 K

The densities and viscosities of several sulfates, viz., ammonium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, zinc sulfate and cadmium sulfate in aqueous binary mixtures of formamide (FA) have been determined at 298.15, 308.15, and 318.15 K and at atmospheric pressure. The ultrasonic speeds of the electrolytic solutions have also been measured at 298.15 K. Apparent molar volumes (ϕ _V ), viscosity B-coefficients and adiabatic compressibilities (K _S) of these electrolytic solutions were calculated from the experimental densitiy, viscosity and acoustic data. The density and viscosity data were evaluated by using Masson’s and Jones-Dole equation respectively; the derived parameters have been analyzed in terms of ion-ion and ion-solvent interactions. The structure making/breaking capacities of the electrolytes have been inferred from the sign of (∂²ϕ _V ⁰/∂T ²) _P . The results showed that all the electrolytes act as structure-makers in these media. Also the compressibility data indicated electrostriction of the solvent molecules around the cations. The activation parameters of viscous flow were also determined and discussed by the application of transition state theory.     

An electroconductivity study on degree of counterion binding or dissociation of a-sulfonatomyristic acid methyl ester micelles in water as a function of temperature

 For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, the differential conductivity (∂κ/∂C) _T , _P vs. square root of concentration (√C) was employed in order to determine not only CMC but also the limiting molar conductance (Λ⁰) and the molar conductance of micellar species (Λ^M). Based on the data of the degree of counterion binding to micelles (β) determined previously at different temperatures ranging 15–50 °C at every 5 °C, the experimental values of the degree of dissociation (ionization) of a micelle (α_EX) were calculated by regarding as α_EX=1−β. The ratio Λ^M/Λ⁰ corresponding to the ratio of slopes below and above CMC in the curve of specific conductivity (κ) vs. concentration (C), which has been often assumed to be the degree of ionization of micelles (α), was compared with the present α_EX. However, the ratio Λ^M/Λ⁰ (=α) was found to have a correlationship with α_EX (=1−β) as α_EX≈0.40×(Λ^M/Λ⁰), or strictly, α_EX=0.40 (Λ^M/Λ⁰)+0.08, indicating that the simple ratio of the slopes below and above CMC in κ vs. C curve is not true for α_EX=1−β. On the other hand, the method proposed by Evans gave a value closer to α_EX compared with the simple ratio. Received: 17 September 1996 Accepted: 8 April 1997     

Anisotropy in the physical properties of UNiGa under high pressure

The linear thermal expansion, compressibility and magnetostriction of UNiGa have been measured under high pressure. Huge anisotropic behaviors are observed in these physical quantities. The linear thermal expansion coefficients are α _a ∼ 16·10⁻⁶ K⁻¹ along thea-axis anda _c ∼5·10⁻⁶ K⁻¹ along thec-axis, and the linear compressibilities at room temperature are κ _a ∼ 3.6·10⁻³ GPa⁻¹ and κ _c ∼ 1.7·10⁻³ GPa⁻¹ alonga-axis andc-axes, respectively. UNiGa orders antiferromagnetically belowT _N=39 K and shows a metamagnetic transition at 4.2 K in magnetic fieldB _C=1 T. It is found thatT _N decreases andB _C increases with increasing pressure.     

Apparent Molar Volumes and Adiabatic Compressibilities of Crown Ethers and Glymes in Aqueous Solutions at Various Temperatures

Apparent molar volumes and adiabatic compressibilities of 18-crown-6,15-crown-5, 12-crown-4, tetraglyme, and triglyme were measured at 15, 25, and40°C. Apparent molar expansibilities andK ^o Tvalues were also determined.The contribution of the -CH₂CH₂O- group to the limiting partial molar volumesand compressibilities of cyclic and open-chain ethers are compared. It isconcluded, on the basis of the compressibility results, that there is a subtle differencebetween the hydration of the ethene-oxide group in cyclic and open-chain ethers.     

Compressibilities of cyclohexane and toluene mixtures at various temperatures

The isothermal compressibilities _T for cyclohexane+toluene mixtures at 25, 35, 45 and 60°C have been determined by direct piezometric measurement. By combining our results with supplementary literature data, we have calculated the isentropic compressibility _S. Values of the excess functions (V^E/_p)_T, _T ^E and _S ^E were also calculated at four temperatures and their behavior as a function of mole fraction and temperature was studied.     

Thermodynamic characteristics of triphenylantimony bis(acetophenoneoximate)

The temperature dependence of heat capacity C _p ^° = f(T) of triphenylantimony bis(acetophenoneoximate) Ph₃Sb(ONCPhMe)₂ was measured for the first time in an adiabatic vacuum calorimeter in the range of 6.5–370 K and a differential scanning calorimeter in the range of 350–463 K. The temperature, enthalpy, and entropy of fusion were determined. Treatment of low-temperature (20 K ≤ T ≤ 50 K) heat capacity was performed on the basis of Debye’s theory of the heat capacity of solids and its multifractal model and, as a consequence, a conclusion was drawn on the type of structure topology. Standard thermodynamic functions C _p ^°(T), H°(T) — H°(0), S°(T), and G°(T) — H°(0) were calculated according to the experimental data obtained for the compound mentioned in the crystalline and liquid states for the range of T → 0–460 K. The standard entropy of the formation of crystalline Ph₃Sb(ONCPhMe)₂ was determined at T = 298.15 K.     

Thermodynamics of cross-linked and branched (co)polymers based on <Emphasis Type="Italic">tris</Emphasis>- and <Emphasis Type="Italic">bis</Emphasis>-(pentafluorophenyl)germanes

The temperature dependence of the heat capacity of cross-linked and branched (co)polymers based on tris- and bis-(pentafluorophenyl)germanes is studied in the temperature range of 6–7 to 535–570 K, using adiabatic vacuum and differential scanning calorimeters. In the indicated temperature range, physical transformations are revealed and their thermodynamic characteristics are determined. The obtained experimental data are used to calculate the thermodynamic functions of (co)polymers: C _p /°, H°(T) - H°(0), S°(T) - S°(0), and G°(T) - H°(0) in the range of T → 0 to 535 K for the branched (co)polymer and from T → 0 to 500 K for the cross-linked polymer. Their standard entropies of formation are determined at 298.15 K. The obtained results are compared with analogous data for hyperbranched perfluorinated polyphenylenegermane studied earlier. The effect of the structure of polyphenylenegermanes on their thermodynamic properties is analyzed.