Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene by using three electroneutral receptors

From extraction experiments and $ \gamma $ -activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3 A^?(aq) + L(nb) $ \Leftrightarrow $ EuL³⁺(nb) + 3A^?(nb) taking place in the two-phase water–nitrobenzene system ( $ {\text{A}}^{ - } = {\text{CF}}_{ 3} {\text{SO}}_{3}^{ - } $ ; L = electroneutral receptors denoted by 1, 2, and 3 – see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the series of 3 < 2 < 1.

Synergistic extraction of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate and bis(diphenylphosphino)methane dioxide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of bis(diphenylphosphino)methane dioxide (DPPMDO, L) has been investigated. The equilibrium data have been explained assuming that the species $ {\text{HL}}^{ + } $ , $ {\text{HL}}_{2}^{ + } $ , $ {\text{ML}}_{2}^{3 + } $ , $ {\text{ML}}_{3}^{3 + } $ and $ {\text{ML}}_{4}^{3 + } $ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the corresponding complexes $ {\text{EuL}}_{n}^{3 + } $ and $ {\text{AmL}}_{n}^{3 + } $ , where n = 2, 3 and L is DPPMDO, in water–saturated nitrobenzene are comparable, whereas in this medium the stability of the cationic species $ {\text{AmL}}_{4}^{3 + } $ (L = DPPMDO) is somewhat higher than that of $ {\text{EuL}}_{4}^{3 + } $ with the same ligand L.     

Experimental and DFT study on complexation of Eu3+ with a macrocyclic lactam receptor

From extraction experiments and $ \gamma $ -activity measurements, the extraction constant corresponding to the equilibrium $ {\text{Eu}}^{ 3+ } \left( {\text{aq}} \right) + 3 {\text{A}}^{ - } \left( {\text{aq}} \right) + {\mathbf{1}}\left( {\text{nb}} \right) \Leftrightarrow {\mathbf{1}} \cdot {\text{Eu}}^{ 3+ } \left( {\text{nb}} \right) + 3 {\text{A}}^{ - } \left( {\text{nb}} \right) $ taking place in the two-phase water–nitrobenzene system ( $ {\text{A}}^{ - } = \text {CF}_{3} \text{SO}_{3}^{ - } $ ; 1 = macrocyclic lactam receptor—see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as $ { \log } K_{{{\text{ex}} }} ({\mathbf{1}} \cdot {\text{Eu}}^{ 3+ } ,{\text{ 3A}}^{ - } )\; = \; - 4. 9 \pm 0. 1 $ . Further, the stability constant of the 1·Eu³⁺ cationic complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: $ { \log } \beta_{{{\text{nb}} }} ({\mathbf{1}} \cdot {\text{Eu}}^{ 3+ } ) \; = \; 8. 2 \pm 0. 1 $ . Finally, using DFT calculations, the most probable structure of the cationic complex species 1·Eu³⁺ was derived. In the resulting 1·Eu³⁺ complex, the “central” cation Eu³⁺ is bound by five bond interactions to two ethereal oxygen atoms and two carbonyl oxygens, as well as to one carbon atom of the corresponding benzene ring of the parent macrocyclic lactam receptor 1 via cation-π interaction.

Extraction of some univalent cations into phenyltrifluoromethyl sulfone by using sodium dicarbollylcobaltate in the presence of benzo-18-crown-6

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺ (aq) + 1·Na⁺ (org) $ \Leftrightarrow $ 1·M⁺ (org) + Na⁺ (aq) taking place in the two-phase water–phenyltrifluoromethyl sulfone (abbrev. FS 13) system (M⁺ = Li⁺, H₃O⁺, NH₄ ⁺, Ag⁺, Tl⁺, K⁺, Rb⁺, Cs⁺; 1 = benzo-18-crown-6; aq = aqueous phase, org = FS 13 phase) were evaluated. Further, the stability constants of the 1·M⁺ complexes in FS 13 saturated with water were calculated; they were found to increase in the series of $ {\text{Cs}}^{ + } \, < \,{\text{Rb}}^{ + } \, < \,{\text{H}}_{ 3} {\text{O}}^{ + } \, < \,{\text{Ag}}^{ + } \, < \,{\text{Li}}^{ + } \, < \,{\text{NH}}_{4}^{ + } \, < \,{\text{K}}^{ + } \, < \,{\text{Tl}}^{ + } $ .     

Density functional study on structures, stabilities, and electronic properties of size-selected Pd n Si q (n = 1–7 and q = 0, +1, −1) clusters

The density functional theory (DFT) calculations within the framework of generalized gradient approximation have been employed to systematically investigate the geometrical structures, stabilities, and electronic properties of Pd _n Si ^q (n = 1–7 and q = 0, +1, ?1) clusters and compared them with the pure ${\text{Pd}}_{n + 1}^{q}$ (n = 1–7 and q = 0, +1, ?1) clusters for illustrating the effect of doping Si atom into palladium nanoclusters. The most stable configurations adopt a three-dimensional structure for both pure and Si-doped palladium clusters at n = 3–7. As a result of doping, the Pd _n Si clusters adopt different geometries as compared to that of Pd _n+1. A careful analysis of the binding energies per atom, fragmentation energies, second-order difference of energies, and HOMO–LUMO energy gaps as a function of cluster size shows that the clusters ${\text{Pd}}_{4}^{ + }$ , ${\text{Pd}}_{4}$ , ${\text{Pd}}_{8}^{ - }$ , ${\text{Pd}}_{5} {\text{Si}}^{0, + , - }$ , and ${\text{Pd}}_{7} {\text{Si}}^{0, + , - }$ possess relatively higher stability. There is enhancement in the stabilities of palladium frameworks due to doping with an impurity atom. In addition, the charge transfer has been analyzed to understand the effect of doped atom and compared further.     

A thermodynamic study of complexation of 18-crown-6 with Zn2+, Tl+, Hg2+ and {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} cations in acetonitrile-dimethylformamide binary media and study the effect of anion on the stability constant of (18C6-Na+) complex in methanol solutions

The equilibrium constants and thermodynamic parameters for complex formation of 18-crown-6(18C6) with Zn²⁺, Tl⁺, Hg²⁺ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations have been determined by conductivity measurements in acetonitrile(AN)-dimethylformamide(DMF) binary solutions. 18-crown-6 forms 1:1 complexes [M:L] with Zn²⁺, Hg²⁺ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations, but in the case of Tl⁺ cation, a 1:2 [M:L₂] complex is formed in most binary solutions. The thermodynamic parameters ( $ \Delta {\text{H}}^{ \circ }_{{\text{c}}} $ and $ \Delta {\text{S}}^{ \circ }_{{\text{c}}} $ ) which were obtained from temperature dependence of the equilibrium constants show that in most cases, the complexes are enthalpy destabilized but entropy stabilized and a non-monotonic behaviour is observed for variations of standard enthalpy and entropy changes versus the composition of AN/DMF binary mixed solvents. The obtained results show that the order of selectivity of 18C6 ligand for these cations changes with the composition of the mixed solvent. A non-linear relationship was observed between the stability constants (logK_f) of these complexes with the composition of AN/DMF binary solutions. The influence of the $ {\text{ClO}}^{ - }_{{\text{4}}} $ , $ {\text{NO}}^{ - }_{{\text{3}}} $ and $ {\text{Cl}}^{ - } $ anions on the stability constant of (18C6-Na⁺) complex in methanol (MeOH) solutions was also studied by potentiometry method. The results show that the stability of (18C6-Na⁺) complex in the presence of the anions increases in order: $ {\text{ClO}}^{ - }_{{\text{4}}} $  >  $ {\text{NO}}^{ - }_{{\text{3}}} $  >  $ {\text{Cl}}^{ - } $ .     

Volumetric Properties of the Nucleoside Thymidine in Aqueous Solution at T = 298.15 K and p = (10 to 100) MPa

Sound speeds have been measured for aqueous solutions of the nucleoside thymidine at T = 298.15 K and at the pressures p = (10, 20, 40, 60, 80, and 100) MPa. The partial molar volumes at infinite dilution, $ V_{2}^{\text{o}} $ , the partial molar isentropic compressions at infinite dilution, $ K_{S,2}^{\text{o}} $ , and the partial molar isothermal compressions at infinite dilution, $ K_{T,2}^{\text{o}} $ $ \{ K_{T,2}^{\text{o}} = - (\partial V_{2}^{\text{o}} /\partial p)_{T} \} $ , have been derived from the sound speeds at elevated pressures using methods described in our previous work. The $ V_{2}^{\text{o}} $ and $ K_{T,2}^{\text{o}} $ results were rationalized in terms of the likely interactions between thymidine and the aqueous solvent. The $ V_{2}^{\text{o}} $ results were also compared with those calculated using the revised Helgeson–Kirkham–Flowers (HKF) equation of state.     

Solvent extraction of microamounts of strontium and barium into nitrobenzene by using synergistic mixture of hydrogen dicarbollylcobaltate and dicyclohexano-18-crown-6

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-18-crown-6 (DCH18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, $ {\text{HL}}_{ 2}^{ + } $ , ML²⁺ and $ {\text{ML}}_{ 2}^{ 2+ } $ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that in the mentioned medium the stability constants of the complexes BaL²⁺ and $ {\text{BaL}}_{2}^{2 + }, $ where L = DCH18C6, are somewhat higher than those of the species SrL²⁺ and $ {\text{SrL}}_{2}^{2 + } $ with the same ligand L.     

Densities and Volumetric Properties of Butyl Acrylate + 1-Butanol, or +2-Butanol, or +2-Methyl-1-propanol, or +2-Methyl-2-propanol Binary Mixtures at Temperatures from 288.15 to 318.15 K

The densities, ρ, of binary mixtures of butyl acrylate with 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, including those of the pure liquids, were measured over the entire composition range at temperatures of (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume $ V_{\text{m}}^{\text{E}} $ V m E , partial molar volumes $ \overline{V}_{\text{m,1}} $ V ¯ m,1 and $ \overline{V}_{\text{m,2}} $ V ¯ m,2 , and excess partial molar volumes $ \overline{V}_{\text{m,1}}^{\text{E}} $ V ¯ m,1 E and $ \overline{V}_{\text{m,2}}^{\text{E}} $ V ¯ m,2 E , were calculated over the whole composition range as were the partial molar volumes $ \overline{V}_{\text{m,1}}^{^\circ } $ V ¯ m,1 ° and $ \overline{V}_{\text{m,2}}^{^\circ } $ V ¯ m,2 ° , and excess partial molar volumes $ \overline{V}_{\text{m,1}}^{{^\circ {\text{E}}}} $ V ¯ m,1 ° E and $ \overline{V}_{\text{m,2}}^{{^\circ {\text{E}}}} $ V ¯ m,2 ° E , at infinite dilution,. The $ V_{\text{m}}^{\text{E}} $ V m E values were found to be positive over the whole composition range for all the mixtures and at each temperature studied, indicating the presence of weak (non-specific) interactions between butyl acrylate and alkanol molecules. The deviations in $ V_{\text{m}}^{\text{E}} $ V m E values follow the order: 1-butanol < 2-butanol < 2-methyl-1-propanol < 2-methyl-2-propanol. It is observed that the $ V_{\text{m}}^{\text{E}} $ V m E values depend upon the position of alkyl groups in alkanol molecules and the interactions between butyl acrylate and isomeric butanols decrease with increase in the number of alkyl groups at α-carbon atom in the alkanol molecules.     

Synergistic extraction of some divalent cations into nitrobenzene by using strontium dicarbollylcobaltate and hexaethyl p- tert-butylcalix[6]arene hexaacetate

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺ (aq) + SrL²⁺ (nb) $ \Leftrightarrow $ ML²⁺ (nb) + Sr²⁺ (aq) taking place in the two-phase water–nitrobenzene system (M²⁺ = Ca²⁺, Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, $ {\text{UO}}_{2}^{2 + } $ , Mn²⁺, Co²⁺, Ni²⁺; L = hexaethyl p-tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML²⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following order: Cd²⁺ < Ca²⁺ < Mn²⁺ < Cu²⁺, Zn²⁺ <  $ {\text{UO}}_{2}^{2 + } $ , Co²⁺ < Ni²⁺ < Sr²⁺ < Pb²⁺.     

Solvent extraction of strontium and barium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexano-24-crown-8

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-24-crown-8 (DCH24C8, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, $ {\text{HL}}_{2}^{ + }, $ ML²⁺ and $ {\text{ML}}_{ 2}^{2 + } $ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that in water–saturated nitrobenzene, the stability constants of the complexes BaL²⁺ and $ {\text{BaL}}_{ 2}{^{2 + }}, $ where L = DCH24C8, are somewhat higher than those of the corresponding species SrL²⁺ and $ {\text{SrL}}_{ 2}{^{2 + }} $ with the same ligand L.     

Correlation consistent, Douglas–Kroll–Hess relativistic basis sets for the 5p and 6p elements

The diatomic carbon molecule has a complex electronic structure with a large number of low-lying electronic excited states. In this work, the potential energy curves (PECs) of the four lowest lying singlet states ( $X^{1} \Sigma^{ + }_{g}$ , $A^{1} \Pi_{u}$ , $B^{1} \Delta_{g}$ , and $B^{\prime1} \Sigma^{ + }_{g}$ ) were obtained by high-level ab initio calculations. Valence electron correlation was accounted for by the correlation energy extrapolation by intrinsic scaling (CEEIS) method. Additional corrections to the PECs included core–valence correlation and relativistic effects. Spin–orbit corrections were found to be insignificant. The impact of using dynamically weighted reference wave functions in conjunction with CEEIS was examined and found to give indistinguishable results from the even weighted method. The PECs showed multiple curve crossings due to the $B^{1} \Delta_{g}$ state as well as an avoided crossing between the two $^{1} \Sigma^{ + }_{g}$ states. Vibrational energy levels were computed for each of the four electronic states, as well as rotational constants and spectroscopic parameters. Comparison between the theoretical and experimental results showed excellent agreement overall. Equilibrium bond distances are reproduced to within 0.05 %. The dissociation energies of the states agree with experiment to within ~0.5 kcal/mol, achieving “chemical accuracy.” Vibrational energy levels show average deviations of ~20 cm^?1 or less. The $B^{1} \Delta_{g}$ state shows the best agreement with a mean absolute deviation of 2.41 cm^?1. Calculated rotational constants exhibit very good agreement with experiment, as do the spectroscopic constants.     

Excess Molar Volumes and Excess Isentropic Compressibilities of o-Toluidine + Tetrahydropyran with Pyridine or Benzene or Toluene Ternary Mixtures at 298.15, 303.15 and 308.15 K

The densities, ρ ₁₂₃, and speeds of sound, u ₁₂₃, of ternary o-toluidine (OT, 1) + tetrahydropyran (THP, 2) + pyridine (Py) or benzene or toluene (3) mixtures have been measured as a function of composition at 298.15, 303.15 and 308.15 K. Values of the excess molar volumes, $ V_{123}^{\text{E}} , $ and excess isentropic compressibilities, $ (\kappa_{\text{S}}^{\text{E}} )_{123} , $ of the studied mixtures have been determined by employing the measured experimental data. The observed thermodynamic properties were fitted with the Redlich–Kister equation to determine adjustable ternary parameters and standard deviations. The $ V_{123}^{\text{E}} $ and $ (\kappa_{\text{S}}^{\text{E}} )_{123} $ values were also analyzed in terms of Graph theory. It was observed that Graph theory correctly predicts the sign as well as magnitude of $ V_{123}^{\text{E}} $ and $ (\kappa_{\text{S}}^{\text{E}} )_{123} $ values of the investigated mixtures. Analysis of the data suggests strong interactions and a more close packed arrangement in OT (1) + THP (2) + Py (3) mixtures as compared to those of the OT (1) + THP (2) + benzene (3) or toluene (3) mixtures. This may be due to the presence of a nitrogen atom in Py which results in stronger interactions for the OT:THP molecular entity as compared to those with benzene or toluene.     

Solvent extraction of calcium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of dicyclohexano-18-crown-6 and dicyclohexano-24-crown-8

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of dicyclohexano-18-crown-6 (DCH18C6, L) and dicyclohexano-24-crown-8 (DCH24C8, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, $ {\text{HL}}_{2}^{ + },$ CaL²⁺ and $ {\text{CaL}}_{2}^{2 + } $ (L = DCH18C6, DCH24C8) are present in the organic phase. The values of extraction and stability constants of the complex species in nitrobenzene saturated with water have been determined. It was found that the stability constants of CaL²⁺ (L = DCH18C6, DCH24C8) for both ligands under study are practically the same in nitrobenzene saturated with water, whereas in this medium the stability of the complex $ {\text{CaL}}_{2}^{2 + } $ involving the DCH24C8 ligand is somewhat higher than that of $ {\text{CaL}}_{2}^{2 + } $ with the ligand DCH18C6.     

Synthesis of lanthanide(III) complexes appended with a diphenylphosphinamide and their interaction with human serum albumin

Two DOTA-based proligands bearing a pendant diphenylphosphinamide 4a and 4b were synthesised. Their Eu(III) complexes exhibit sensitised emission when excited at 270 nm via the diphenylphosphinamide chromophore. Hydration states of q = 1.5 were determined from excited state lifetime measurements (Eu.4a $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 2. 1 4 \,{\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 0. 6 4 \,{\text{ms}}^{ - 1} $ ; Eu.4b $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 2. 6 7\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 1. 1 8 \,{\text{ms}}^{ - 1} $ ). In the presence of human serum albumin (HSA) (0.1 mM Eu.4a/b, 0.67 mM HSA, pH 7.4) q = 0.4 for Eu.4a ( $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 1. 3 4\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 0. 7 5\, {\text{ms}}^{ - 1} $ ) and q = 0.6 for Eu.4b ( $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 1. 8 3\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 1.0 5 \,{\text{ms}}^{ - 1} $ ). Relaxivites (pH 7.4, 298 K, 20 MHz) of the Gd(III) complexes in the absence and presence of HSA (0.1 mM Gd.4a/b, 0.67 mM HSA) were: Gd.4a (r ₁ = 7.6 mM^?1s^?1 and r ₁ = 11.7 mM^?1s^?1) and Gd.4b. (r ₁ = 7.3 mM^?1s^?1 and r ₁ = 16.0 mM^?1s^?1). These relatively modest increases in r ₁ are consistent with the change in inner-sphere hydration on binding to HSA shown by luminescence measurements on Eu.4a/b. Binding constants for HSA determined by the quenching of luminescence (Eu) and enhancement of relaxivity (Gd) were Eu.4a (27,000 M^?1 ± 12%), Eu.4b (32,000 M^?1 ± 14%), Gd.4a (21,000 M^?1 ± 15%) and Gd.4b (26,000 M^?1 ± 15%).     

Thermodynamic study of metal corrosion and inhibitor adsorption processes in copper/N-1-naphthylethylenediamine dihydrochloride monomethanolate/nitric acid system: part 2

N-1-Naphthylethylenediamine dihydrochloride monomethanolate (N-NEDHME) was tested as a corrosion inhibitor for copper in 2 M HNO₃ solution using the standard gravimetric technique at 303–343 K. N-NEDHME acts as an inhibitor for copper in an acidic medium. Inhibition efficiency increases with increase in concentration of N-NEDHME but decreases with a rise in temperature. Thermodynamic parameters such as adsorption heat ( $ \Updelta H_{\text{ads}}^\circ $ ), adsorption entropy ( $ \Updelta S_{\text{ads}}^\circ $ ) and adsorption free energy ( $ \Updelta G_{\text{ads}}^\circ $ ) were obtained from experimental data of the temperature studies of the inhibition process at five temperatures ranging from 303 to 343 K. Kinetic parameters activation such as $ E_{a} $ , $ \Updelta H_{\text{a}}^\circ $ , $ \Updelta S_{\text{a}}^\circ $ and pre-exponential factors have been calculated and are discussed. Adsorption of N-NEDHME on the copper surface in 2 M HNO₃ follows the Langmuir isotherm model.     

Thermochemical Properties of n-Undecylammonium Bromide Monohydrate C11H28BrNO(s)

The crystal structure of n-undecylammonium bromide monohydrate was determined by X-ray crystallography. The crystal system of the compound is monoclinic, and the space group is P2₁/c. Molar enthalpies of dissolution of the compound at different concentrations m/(mol·kg^?1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. According to the Pitzer’s electrolyte solution model, the molar enthalpy of dissolution of the compound at infinite dilution ( $ \Updelta_{\text{sol}} H_{\text{m}}^{\infty } $ ) and Pitzer parameters ( $ \beta_{\text{MX}}^{(0)L} $ and $ \beta_{\text{MX}}^{(1)L} $ ) were obtained. Values of the apparent relative molar enthalpies ( $ {}^{\Upphi }L $ ) of the title compound and relative partial molar enthalpies ( $ \bar{L}_{2} $ and $ \bar{L}_{1} $ ) of the solute and the solvent at different concentrations were derived from experimental values of the enthalpies of dissolution.     

Thermal analysis, phase transitions and molecular reorientations in [Sr(OS(CH3)2)6](ClO4)2

Thermal analysis (TG/DTG/QMS), performed for [Sr(OS(CH₃)₂)₆](ClO₄)₂ in a flow of argon and in temperature range of 295–585 K, indicated that the compound is completely stable up to ca. 363 K, and next starts to decompose slowly, and in the temperature at ca. 492 K looses four (CH₃)₂SO molecules per one formula unit. During further heating [Sr(DMSO)₂](ClO₄)₂ melts and simultaneously decomposes with explosion. Differential scanning calorimetry (DSC) measurements performed in the temperature range of 93–370 K for [Sr(DMSO)₆](ClO₄)₂ revealed existence of the following phase transitions: glass ? crystal phase Cr5 at T _g  ≈ 164 K (235 K), phase Cr5 → phase Cr4 at $ T_{\text{c6}}^{\text{h}} $  ≈ 241 K, phase Cr4 → phase Cr3 at $ T_{\text{c5}}^{\text{h}} $  ≈ 255 K, phase Cr3 → phase Cr2 at $ T_{\text{c4}}^{\text{h}} $  ≈ 277 K, phase Cr2 ? phase Cr1 at $ T_{\text{c3}}^{\text{h}} $  ≈ 322 K and $ T_{\text{c3}}^{\text{c}} $  ≈ 314 K, phase Cr1 ? phase Rot2 at $ T_{\text{c2}}^{\text{h}} $  ≈ 327 K and $ T_{\text{c2}}^{\text{c}} $  ≈ 321 K and phase Rot2 ? phase Rot1 at $ T_{\text{c1}}^{\text{h}} $  ≈ 358 K and $ T_{\text{c1}}^{\text{c}} $  ≈ 347 K. Entropy changes values of the phase transitions at $ T_{\text{c1}}^{\text{h}} $ and $ T_{\text{c2}}^{\text{h}} $ (?S ≈ 79 and 24 J mol^?1 K^?1, respectively) indicated that phases Rot1 and Rot2 are substantially orientationally disordered. The solid phases (Cr1–Cr5) are more or less ordered phases (?S ≈ 7, 10, 4 and 3 J mol^?1 K^?1, respectively). Phase transitions in [Sr(DMSO)₆](ClO₄)₂ were also examined by Fourier transform middle infrared spectroscopy (FT-MIR). The characteristic changes in the FT-MIR absorption spectra of the low- and high-temperature phases observed at the phase transition temperatures discovered by DSC allowed us to relate these phase transitions to the changes of the reorientational motions of DMSO ligands and/or to the crystal structure changes.     

Temperature Dependence of the Parameter of the SIT Model for Activity Coefficients of 1:1 Electrolytes

This work analyzes the temperature dependence of the only fitting parameter of the SIT (Specific Ion Interaction Theory) model for activity coefficients. Relations based on the so-called “primitive” model for the inter-ionic potential suggest that the binary interaction parameter is proportional to the pure water density. In order to check this correlation, activity coefficients and related data are tested for twenty 1:1 electrolytes, where the necessary data are available at temperatures up to at least 523 K. A strong correlation with water density is universally observed at temperatures T > 360 K (or water densities, $ \rho_{1}^{*} $ ρ 1 ? , below 950 kg·m^?3). In accordance with expectations from theoretical considerations, at these temperatures and water densities, the SIT parameter is constant under isochoric conditions (a constant water density), and decreases with decreases of $ \rho_{1}^{*} $ ρ 1 ? . Over the whole temperature range, usually between 273 and 573 K, the temperature and water density dependence of the SIT model interaction parameters, $ \varepsilon_{\gamma } (M,X) $ ε γ ( M , X ) , where M stands for a cation and X for an anion, is well described (including data at pressures up to 100 MPa) by the following expression $ \varepsilon_{\gamma } (M,X) = b_{0} + b_{1} \rho_{1}^{*} + \frac{{b_{2} }}{T - 210} $ ε γ ( M , X ) = b 0 + b 1 ρ 1 ? + b 2 T ? 210 .     

Transport of Water by Group 1 and 2 Ions with t-Butyl Alcohol as Reference Substance: Comparison with Raffinose and Dioxan

Measurement of the transport of water with respect to the second solvent component in a binary aqueous mixture gives the Washburn number, $ w_{\text{W}} = (n_{\text{W}} )_{ + } t_{ + } - (n_{\text{W}} )_{ - } t_{ - } $ , in a transport number determination, where the ions move in opposite directions, and give the Erdey–Grúz number, $ \Upsigma n_{\text{W}} = (n_{\text{W}} )_{ + } + (n_{\text{W}} )_{ - } $ , in a diffusion experiment, where the ions move in the same direction. Here n _W and t are the number of water molecules and transport number, respectively, of the anion or cation. Combination of the results of these two experiments allows unambiguous determination of values for the solvent transport numbers, $ n_{\text{W}} $ , of the individual ions. While the values of $ n_{\text{W}} $ depend on the cosolvent, at high dilutions of the second component the highest value of $ n_{\text{W}} $ found, $ N_{\text{W}} $ , should approach the number of water molecules transported by the ion in pure water, $ N_{\text{W}}^{0} $ . New data for alkali-metal, alkaline-earth metal, hydrogen and halide ions in dilute mixtures of t-butyl alcohol with water are presented. Values of $ N_{\text{W}} $ rounded to whole numbers thus found are: 12 (Li⁺), 10 (Na⁺), 6 (K⁺), 5 (Rb⁺), 5 (Cs⁺), 1 (H⁺), 13 (Ca²⁺), 16 (Sr²⁺) and 15 (Ba²⁺). Factors influencing preferential solvation are briefly discussed. Detailed recalculations of $ n_{\text{W}} $ in the raffinose–water system from literature data also allows resolution of a problem with the Onsager Relations.