Thermal properties of <Emphasis Type="Italic">n</Emphasis>-R<Subscript>4</Subscript>NBr solutions in binary solvents containing formamide

The enthalpies of solution of tetraethyl- and tetra-n-hexylammonium bromides have been measured in mixtures of formamide with ethylene glycol at 298.15 and 313.15 K in the whole mole fraction range by the calorimetric method. The standard enthalpies of solution in binary mixtures have been calculated with Redlich–Rosenfeld–Meyer type equation. The enthalpy and heat capacity parameters of pair interaction of organic electrolytes with EG in FA and with FA in EG have been computed and discussed. The enthalpy interaction parameters of single ions with EG in FA medium have been evaluated and compared with those for ion–water and ion–MeOH interaction in FA. The standard heat capacities of solution have been evaluated. The excess enthalpies of solution, Δ_sol H ^E, of Et₄NBr, Bu₄NBr, and Hex₄NBr have been determined. The Δ_sol H ^E values are positive for Et₄NBr and negative for Bu₄NBr and Hex₄NBr and become more negative from Bu₄NBr to Hex₄NBr.     

Crystal structure determination of complexes of monomethylammonium chloride and mercury(II) chloride: CH3NH3HgCl3, (CH3NH3)2HgCl4, and CH3NH3Hg2Cl5

The crystal structures have been determined of CH₃NH₃HgCl₃, (CH₃NH₃)₂HgCl₄, and CH₃NH₃Hg₂Cl₅. In (CH₃NH₃)₂HgCl₄ the Hg^II atom is tetrahedrally coordinated by four Cl atoms with Hg? Cl bond lengths of 2.464 to 2.478 Å. In the other two compounds the Hg^II atom is involved in two short covalent Hg? Cl bonds, forming a pseudo HgCl₂ molecule and two much longer bridging Hg? Cl bonds. The methylammonium groups are connected by hydrogen bonds to the chlorine atoms. The nature of the hydrogen bonding scheme probably causes disorder of the methylammonium groups.     

Measurement and Correlation of Excess Molar Enthalpy of Binary Mixtures Containing Butyl Acetate + 1-Alkanols (C1–C6) at 298.15 K

Excess molar enthalpies, ?H _m ^E , for the binary mixtures of butyl acetate + 1-alkanols, namely (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol), were measured over the whole range of composition at 298.15 K using a Parr 1455 solution calorimeter. The excess partial molar enthalpies, ?H _m,i ^E , were calculated from the experimental excess molar enthalpies using the Redlich–Kister polynomial equation. The sign of ?H _m ^E for all systems are positive because of the disruption of hydrogen bonding and dipole–dipole interactions in the alkanols and esters, respectively. The magnitude of the ?H _m ^E values increases with increasing alkyl chain length. The behavior of ?H _m ^E was analyzed in terms of the length of the alkanol chain, the nature and type of intermolecular interactions and the balance between positive and negative effects on deviations from ideality. The experimental excess molar enthalpy data have also been correlated using the Redlich–Kister and SSF equations and two local composition models (UNIQUAC and NRTL).     

The phase diagrams of the CdCl2-NaCl-H2O system at 298 K

Solid-liquid equilibrium of ternary system Cd²⁺, Na⁺//Cl^?-H₂O at 298 K were studied by an isothermal solution saturation method. Experimental results indicate that there are three univariant curves AE, EF, and FB, two invariant points E, F, and three crystallization fields in the ternary system. The ternary system has one double salt Na₂CdCl₄ · 3H₂O. The crystallization zones of equilibrium solid phases are CdCl₂ · H₂O (AEG field), Na₂CdCl₄ · 3H₂O (EFM field), and NaCl (FBN field), respectively. The composition of the invariant point E is CdCl₂ · H₂O and Na₂CdCl₄ · 3H₂O of which content was 52.70 and 4.11%, respectively. The composition of the invariant point F is Na₂CdCl₄ · 3H₂O and NaCl of which content was 27.92 and 14.95%, respectively. The density of solution in the ternary system show regular changes along with the increased cadmium concentration. The results indicated that CdCl₂ · H₂O possessed the highest solubility among those three salts, which means a strong transfer of Cd ion and a high pollution risk of soil environment. And the solubility of NaCl would be restrained as the three salts existing together.     

Organic-inorganic hybrid perovskite (C<Subscript>6</Subscript>H<Subscript>5</Subscript>(CH<Subscript>2</Subscript>)<Subscript>2</Subscript>NH<Subscript>3</Subscript>)<Subscript>2</Subscript>CdCl<Subscript>4</Subscript>: Synthesis,structural and thermal properties

The present research work reports the study on crystal structure, vibrational spectroscopy and thermal analysis of organic-inorganic hybrid compound (C₆H₅(CH₂)₂NH₃)₂CdCl₄. Single crystals of bis(phenethylammonium)tetrachlorocadmate (C₆H₅(CH₂)₂NH₃)₂CdCl₄ (PEA–Cd) were obtained by diffusion at room temperature. This compound crystallizes in the orthorhombic space group C2cb with unit cell parameters a = 7.4444(2) Å, b = 38.8965(3) Å, c = 7.3737(2) Å and Z = 4. Single crystal structure has been solved and refined to R = 0.036 and wR = 0.092. The structure consists of an extended [CdCl₄]^2– network and two [C₆H₅(CH₂)₂NH₃]⁺ cations to form a two-dimensional perovskite system. The infrared (IR) spectrum of the title compound was recorded at room temperature. Differential scanning calorimetry (DSC) was used to investigate the phase transition; this compound exhibits a reversible single solid-solid phase transition.     

Correlation of the prigogine-flory theory with isothermal compressibility and excess enthalpy data for benzene +n-alkane mixtures

Isothermal compressibilitiesκ _T for benzene + n-alkane systems at 25, 35, 45, and 60°C have been used to check the Prigogine-Flory theory using the van der Waals and Lennard-Jones potentials in order to study the energy-volume dependence. The Flory interaction parameter χ₁₂ has also been calculated for those set of systems at four temperatures. The variation of χ₁₂ with the number of carbon atoms in the n-alkane was studied. Three excess functions have been obtained from χ₁₂ for the equimolecular mixture: (?V ^E/?p)_T which is related toκ _T ^E , the excess enthalpy H ^E , and the excess volume V ^E . Except for H ^E theoretical predictions using a Lennard-Jones potential are in good agreement with the experimental data. A similar treatment has been performed for the same set of systems but using H ^E data at 25°C. The theory, using a van der Waals potential, predicts correctly the variation of the three excess functions with the chain length of the n-alkane but using a Lennard-Jones potential results in better agreement for the order in the magnitude of these excess functions.     

Structure et étude raman du composé (C3H7NH3)2HgCl4

The structure of (C₃H₇NH₃)₂HgCl₄ is orthorhombic, M_r = 462.6, Abma, a = 7.991(2) Å, b = 7.779(2) Å, c = 23.519(2) Å, Z = 4, V = 1462(1) ų, D_m = 2.05(2), D_x = 2.10 mg/m⁻³, λ(AgKα) = 0.56083 Å, μ(AgKα) = 61.02 cm⁻¹, T = 300 K, R = 0.032, R₂ = 0.027 for 1188 reflections with I < 0.5σ(I). The structure is of the K₂NiF₄ type and consists of HgCl₆ octahedra which are held together through equatorial Cl atoms forming a two-dimensional (HgCl₄)²⁻_n layer perpendicular to the c axis (HgCl_ax is shorter than the HgCl_eq). The C₃H₇NH⁺₃ cations inserted between these layers are disordered and joined to the layers by hydrogen bonding. The Raman spectra between 10 and 400 cm⁻¹ have been recorded and some characteristic (HgCl₄)²ⁿ⁻_n layer frequencies assigned. Thermal analysis indicates two singularities at 195 and 205 K.     

Calorimetric investigation of the RbFRb2SO4 liquid system and comparison of the excess thermodynamic functions in the AFA2SO4 (ALi,Na, K,Rb) molten salt mixtures

The experimental values of the excess enthalpy, obtained by direct calorimetry, are reported in this work for the RbFRb₂SO₄ liquid system. The entropy of mixing of this system was calculated from the equilibrium phase diagram.Many expressions have been presented in the literature for the ideal entropy of mixing of ABin2A′B asymmetrical systems and we have pointed out, here, a criterion allowing the selection of one of them for a further evaluation of the excess entropy.A comparative study of the thermodynamic excess functions (δH,δS^E)was carried out on the series of AFA₂SO₄ mixtures (ALi, Na, K, Rb).     

Structure of aminonitrones and electronic effect of substituents on their acid-base properties

A series of para-substituted aromatic aminonitrones p-RC₆H₄C(NH₂)=N⁺(Me)O^– (R = NMe₂, H, Br, Cl, CF₃) have been prepared. Acidity constants of the conjugate acids RC₆H₄C(NH₂)N⁺(Me)OH at 25°C in a EtOH–H₂O mixture (5: 95) have been determined by potentiometric titration. A linear correlation between log (k_R/k_H) and σ_para values has been revealed, and a ρ²⁹⁸(σ_para) parameter has been determined as of 0.635.     

The standard enthalpies of formation of cyclohexylamine and cyclohexylamine hydrochloride

The standard enthalpy of combustion of cyclohexylamine has been measured in an aneroid rotating-bomb calorimeter. The value ΔH_o^o(c-C₆H₁₁NH₂, 1) = ?(4071.3 ± 1.3) kJ mol^?1 yields the standard enthalpy of formation ΔH_f^o(c-C₆H₁₁NH₂, 1) = ?(147.7 ± 1.3) kJ mol^?1. The corresponding gas-phase standard enthalpy of formation for cyclohexylamine is ΔH_f^o(c-C₆H₁₁NH₂, g) = ?(104.9 ± 1.3) kJ mol^?1. The standard enthalpy of formation of cyclohexylamine hydrochloride, ΔH_f^o(c-C₆H₁₁NH₂·HCl, c) = ?(408.2 ± 1.5) kJ mol^?1, was derived by combining the measured enthalpy of solution of the salt in water, literature data, and the ΔH_c^o measured in this study. Comment is made on the thermochemical bond enthalpy H(CN).     

Thermodynamics of liquid propane + cyclopropane

The vapour pressure differences between a mixture of (propane + cyclopropane) and cyclopropane and between propane and cyclopropane have been measured simultaneously with the absolute vapour pressure of cyclopropane. This was done at 13 temperatures between 175 K and 210 K, as a function of composition. The mixtures show small positive deviations from Raoult's law. The excess molar Gibbs energy (G_m^E) has been calculated from the vapour pressure data fitted to the equation G_m^E/(RTx₁x₂ = (−0.2490±0.0072)+(81.8±1.4)/T. The estimated value of the excess molar enthalpy (H_m^E) for the equimolar composition, in the same temperature range is 170 ± 4 J mol⁻¹. The results were interpreted using Deiters' equation of state.     

A one‐dimensional ladder‐like six‐coordinate cadmium polymer: catena‐poly[bis[(S)‐2‐methylpiperazine‐1,4‐diium] [bis[trichloridocadmium(II)]‐di‐μ3‐chlorido]]

The crystal structure of the title compound {(C₅H₁₄N₂)₂[Cd₂Cl₈]}_n, (I), consists of hydrogen‐bonded 2‐methylpiperazinediium (H₂MPPA²⁺) cations in the presence of one‐dimensional polymeric {[CdCl₃(μ₃‐Cl)]²⁻}_n anions. The Cd^II centres are hexacoordinated by three terminal chlorides and three bridging chlorides and have a slightly distorted octahedral CdCl₃(μ₃‐Cl)₃ arrangement. The alternating CdCl₆ octahedra form four‐membered Cd₂Cl₂ rings by the sharing of neighbouring Cd–Cl edges to give rise to extended one‐dimensional ladder‐like chains parallel to the b axis, with a Cd...Cd distance of 4.094 (2) Å and a Cd...Cd...Cd angle of 91.264 (8)°. The H₂MPPA²⁺ cations crosslink the [CdCl₃(μ₃‐Cl)]_n chains by the formation of two N—H...Cl hydrogen bonds to each chain, giving rise to one‐dimensional ladder‐like H₂MPPA²⁺–Cl₂ hydrogen‐bonded chains [graph set R₄²(14)]. The [CdCl₃(μ₃‐Cl)]_n chains are interwoven with the H₂MPPA²⁺–Cl₂ hydrogen‐bonded chains, giving rise to a three‐dimensional supramolecular network.     

New approach to simplify the equation for the excess Gibbs free energy of aqueous solutions of electrolytes applied to the modelling of the NH3–CO2–H2O vapour–liquid equilibria

A new, simple, empirical equation for G^E (excess Gibbs free energy) of electrolyte solutions is proposed in which, contrary to the commonly used Pitzer equation, binary and ternary interaction parameters relate to the interactions of electrolytes in a solution rather than to the interactions of real species in a solution (i.e., anions, cations and nondissociated molecules). Such an approach radically reduces the number of parameters in the new equation for G^E as compared with the Pitzer equation and consequently significantly simplifies their calculation. The efficiency of the new approach is demonstrated on the example of modelling the vapour–liquid equilibria of the industrially important and widely investigated NH₃–CO₂–H₂O system.     

The excess enthalpies of (carbon dioxide + cyclohexane) at 308.15, 358.15, and 413.15 K from 7.50 to 12.50 MPa

The excess molar enthalpies H_m^E for (carbon dioxide + cyclohexane) were measured in the vicinity of their critical locus and in the supercritical region. Mixtures at 308.15 K and at 7.50 MPa show very exothermic mixing and a region where H_m^E varies linearly with mole fraction x while at 10.50 and 12.50 MPa they show only moderately endothermic mixing. Mixtures at 358.15 and 413.15 K and at all pressures studied except for 358.15 K and 12.50 MPa have an exothermic section in the cyclohexane-rich region, a linear section which starts at a mole fraction x corresponding very closely to that of the minimum value of H_m^E, and an endothermic section in the carbon-dioxide-rich region. The H_m^E results exhibiting a linear section allow the determination of values for the vapor and liquid equilibrium-phase compositions. The changes observed in the excess enthalpy with both pressure and temperature are discussed in terms of liquid-vapor equilibrium and critical constants for (carbon dioxide + cyclohexane).     

Enthalpie de dissolution du fluorure et de l′hydrogenofluorure d'ammonium dans les solutions d'acide fluorhydrique

The standard enthalpies of solution of NH₄F and NH₄HF₂ in aqueous solutions of hydrogen fluoride (in the range of concentration 0–30 mol.1^?1) have been measured and from these results the standard enthalpy of formation of NH₄HF_2(c) has been derived as: δH^o_fNH₄HF_2(c) = ?809.9 ± 0.9 kJ.mol^?1     

The Phase Diagram and the Application for the Quaternary System K+, $$ {\text{NH}}{_4^{+}} $$//Cl−, $$ {\text{SO}}{_4^{2 -}} $$SO42-–H2O at 80.0 °C

The solubilities in the quaternary system K⁺, \( {\text{NH}}{_4^{+}} \)//Cl^?, \( {\text{SO}}{_4^{2-}} \)–H₂O and its two ternary subsystems NH₄Cl–KCl–H₂O, (NH₄)₂SO₄–K₂SO₄–H₂O at 80.0 °C were measured using the isothermal dissolution equilibrium method under atmospheric pressure, and the corresponding phase diagrams were plotted. In the phase diagram of the NH₄Cl–KCl–H₂O system, there are three crystalline zones, which correspond to (K_1?m,(NH₄)_m)Cl, ((NH₄)_n,K_1?n)Cl and the co-existence zone of (K_1?m,(NH₄)_m)Cl and ((NH₄)_n,K_1?n)Cl, respectively. In the phase diagram of the (NH₄)₂SO₄–K₂SO₄–H₂O system, there is only one crystalline zone for (K_1?t,(NH₄)_t)₂SO₄. In the phase diagram of the K⁺, \( {\text{NH}}{_4^{+}} \)//Cl^?, \( {\text{SO}}{_4^{2-}} \)–H₂O system, there are three crystal zones, which correspond to (K_1?t,(NH₄)_t)₂SO₄, (K_1?m,(NH₄)_m)Cl and ((NH₄)_n,K_1?n)Cl, respectively. According to the analysis and the calculations for the phase diagrams of the K⁺, \( {\text{NH}}{_4^{+}} \)//Cl^?, \( {\text{SO}}{_4^{2 -}} \)–H₂O system at 80.0 °C and 50.0 °C, this paper proposes a technological process. In the process, the (K_1?t,(NH₄)_t)₂SO₄ can be prepared at 80.0 °C and the ((NH₄)_n,K_1?n)Cl can crystallize out at 50.0 °C. The mass fraction of K₂SO₄ in product L₁ (K_1?t,(NH₄)_t)₂SO₄ (t?=?0.1465) is 88.48%. The composition of solid solutions in the K⁺, \( {\text{NH}}{_4^{+}} \)//Cl^?, \( {\text{SO}}{_4^{2 -}} \)–H₂O system was experimentally determined and then theoretical calculations about the process can be carried out.     

Measurements of excess molar enthalpy and excess molar heat capacity of (1-heptanol or 1-octanol)+(diethylamine or <Emphasis Type="Italic">s</Emphasis>-butylamine) mixtures at 298.15 K and 0.1 MPa

Experimental data of excess molar enthalpy (H _m^E) and excess molar heat capacity (C _pm^E) of binary mixtures containing (1-heptanol or 1-octanol)+(diethylamine or s-butylamine) have been determined as a function of composition at 298.15 K and at 0.1 MPa using a modified 1455 Parr solution calorimeter. The excess molar enthalpy data are negative and show parabolic format over the whole composition range; however, the excess molar heat capacity values, whose curves show a S-shape, are positive in the 0.0 to 0.7 molar fraction range and negative between the molar fraction values 0.7 to 1.0. The applicability of the ERAS-model to correlate the excess molar enthalpy data was tested. The calculated data values are in good agreement with the experimental ones. The experimental behavior of H _m^E is interpreted in terms of specific interactions between 1-alkanol and amine molecules.     

Zwei Mercuri‐Ammin‐Komplexe: [Hg(NH3)2][HgCl3]2 und [Hg(NH3)4](ClO4)2

Two Mercuric Ammoniates: [Hg(NH₃)₂][HgCl₃]₂ and [Hg(NH₃)₄](ClO₄)₂ [Hg(NH₃)₂][HgCl₃]₂ ( 1 ) is obtained by saturating an equimolar solution of HgCl₂ and NH₄Cl with Hg(NH₂)Cl at 75 °C. 1 crystallizes in the orthorhombic space group Pmna with a = 591.9(1) pm, b = 800.3(1) pm, c = 1243.3(4) pm, Z = 2. The structure consists of linear cations [Hg(NH₃)₂]²⁺ and T‐shaped anions [HgCl₃]^—. The coordination sphere of mercury is ?effectively”? completed to compressed hexagonal bipyramids and distorted octahedra, respectively. Single crystals of [Hg(NH₃)₄](ClO₄)₂ ( 2 ) are obtained by passing gaseous ammonia through a solution of mercuric perchlorate, while the solution was cooled to temperatures below 10 °C. 2 crystallizes in the monoclinic space group P2₁/c with a = 791.52(9) pm, b = 1084.3(2) pm, c = 1566.4(2) pm, β = 120.352(1)°, Z = 4. The structure consists of compressed [Hg(NH₃)₄]²⁺ tetrahedra and perchlorate anions. The packing of the heavy atoms Hg and Cl is analogous to the baddeleyite (α‐ZrO₂) type of structure.     

Synthesis,non-isothermal kinetic and thermodynamic studies of the formation of LiMnPO4 from NH4MnPO4·H2O precursor

NH₄MnPO₄·H₂O was successfully synthesized by precipitating method. The LiMnPO₄ was successfully generated through solid state reaction between synthesized NH₄MnPO₄·H₂O precursor and Li₂CO₃. The morphologies were observed to depend on the reaction temperatures. The thermal decomposition of NH₄MnPO₄·H₂O and the formation process of LiMnPO₄ were confirmed by TG/DTG/DTA, FTIR, AAS/AES, XRD and SEM methods. The average crystallite size of NH₄MnPO₄·H₂O, Mn₂P₂O₇ and LiMnPO₄ were found to be around 51.2, 44.9 and 48.1 nm, respectively. The non–isothermal kinetic parameters (kinetic triplet: E_α, A, g(α)) of the formation process of LiMnPO₄ were evaluated from TG data by using Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of E_α. The Coats–Redfern equation and kinetic compensation effects were successfully applied to confirm the activation energy and the most probable mechanism functions of the formation of LiMnPO₄. The thermodynamic functions (ΔH^≠, ΔS^≠, ΔG^≠) of the transition state complexes of the formation of LiMnPO₄ were calculated from the kinetic parameters for the first time.