Surface tension of dimethyl ether + propane from 243 to 333 K

The surface tension of the binary refrigerant mixture dimethyl ether (RE170)(1) + propane (R290)(2) at three mass fraction of w₁=0.3007,0.4975 ??and ??0.6949$w_1=\mathrm{0.3007,0.4975}\text{\hspace{0.17em}??}\text{and}\text{\hspace{0.17em}??}0.6949$ was measured in the temperature range from 243 to 333 K with a differential capillary rise method. The uncertainties of the measurement of the temperature and the surface tension were estimated to be within ±10 mK and ±0.2 mN m⁻¹, respectively. A correlation for the surface tension of the binary refrigerant mixture RE170 + R290 was developed as a function of the composition.     

Activity coefficients of NaCl in PEG 4000 + water mixtures at 288.15, 298.15 and 308.15 K

The electromotive force of the cell containing two ion-selective electrodes (ISE),

Na-ISE|NaCl (m), PEG ??4000 (Y), H₂O (100−Y)|Cl-ISE$\text{Na-ISE}|\text{NaCl}(m),\text{PEG}\text{\hspace{0.17em}??}4000(Y),{\text{H}}_2\text{O}(100-Y)|\text{Cl-ISE}$

Solubility of carbon dioxide in the solvent system (2-amino-2-methyl-1-propanol + sulfolane + water)

New sets of data for the solubility of CO₂ in the amine solvent system of 2-amino-2-methyl-1-propanol (1) + sulfolane (2) + water (3) were presented in this work. The measurements were done at temperatures of 313.2, 333.2, 353.2, and 373.2 K and CO₂ partial pressures up to 193 kPa. The investigated compositions were as follows: (i) w₁=16.5%$w_1=16.5\%$, w₂=32.2%$w_2=32.2\%$; (ii) w₁=8.2%$w_1=8.2\%$, w₂=41.2%$w_2=41.2\%$; (iii) w₁=22.3%$w_1=22.3\%$, w₂=27.7%$w_2=27.7\%$; and (iv) w₁=30.6%$w_1=30.6\%$, w₂=19.4%$w_2=19.4\%$, where w$w$ is the mass percent of the component. The present solubility data was correlated by a modified Kent–Eisenberg model. The model reasonably represents the present solubility data, not only over the considered conditions, but also for a wider range of temperatures, partial pressures, and compositions.     

Thermodynamic properties of the ternary system {yNH4Cl + (1 − y)MgCl2} (aq) at 298.15 K

The mixture {yNH₄Cl + (1 − y)MgCl₂} (aq) has been studied using the hygrometric method at the temperature 298.15 K. The water activities are measured at total molalities from 0.30 mol kg⁻¹ up to saturation for different ionic strength fractions y of NH₄Cl with y = 0.20, 0.50 and 0.80. The obtained data allow the deduction of osmotic coefficients. Experimental results are compared with the calculations using the models of Zdanovskii–Stokes–Robinson, Kusik and Meissner, Robinson and Stokes, Lietzke and Stoughton, Reilly–Wood and Robinson and Pitzer. Thermodynamic properties have been modeled using the Pitzer ion-interaction model with inclusion of an ionic strength dependence of the third virial coefficient for the binary systems. From these measurements and the obtained binary parameters β⁽⁰⁾, β⁽¹⁾, C⁽⁰⁾ and C⁽¹⁾, the mixing ionic parameters θNH₄Mg${\theta }_{\text{N}{\text{H}}_4\text{Mg}}$ and ψNH₄MgCl${\psi }_{\text{N}{\text{H}}_4\text{MgCl}}$ are determined by the standard Pitzer model. The results show that a good accuracy is obtained with the standard Pitzer model using extended binary parameters. The parameters θNH₄Mg${\theta }_{\text{N}{\text{H}}_4\text{Mg}}$ and ψNH₄MgCl${\psi }_{\text{N}{\text{H}}_4\text{MgCl}}$ were used for evaluation of activity coefficients in the mixture. The excess Gibbs energy is also determined.     

Iron organic speciation determination in rainwater using cathodic stripping voltammetry

A sensitive method using Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) has been developed to determine for the first time iron (Fe) organic speciation in rainwater over the typical natural range of pH. We have adapted techniques previously developed in other natural waters to rainwater samples, using the competing ligand 1-nitroso-2-naphthol (NN). The blank was equal to 0.17 ± 0.05 nM (n = 14) and the detection limit (DL) for labile Fe was 0.15 nM which is 10–70 times lower than that of previously published methods. The conditional stability constant for NN under rainwater conditions was calibrated over the pH range 5.52–6.20 through competition with ethylenediaminetetraacetic acid (EDTA). The calculated value of the logarithm of β^′_Fe3+(NN)3${{\beta }^{\prime }}_{{\text{Fe}}^{3+}{(\text{NN})}_3}$ increased linearly with increasing pH according to log β^′_Fe3+(NN)3=2.4±0.6×pH+11.9±3.5$\text{log}{{\beta }^{\prime }}_{{\text{Fe}}^{3+}{(\text{NN})}_3}=2.4\pm 0.6\times \text{pH}+11.9\pm 3.5$ (salinity = 2.9, T = 20 °C). The validation of the method was carried out using desferrioxamine mesylate B (DFOB) as a natural model ligand for Fe. Adequate detection windows were defined to detect this class of ligands in rainwater with 40 μM of NN from pH 5.52 to 6.20. The concentration of Fe-complexing natural ligands was determined for the first time in three unfiltered and one filtered rainwater samples. Organic Fe-complexing ligand concentrations varied from 104.2 ± 4.1 nM equivalent of Fe(III) to 336.2 ± 19.0 nM equivalent of Fe(III) and the logarithm of the conditional stability constants, with respect to Fe³⁺, varied from 21.1 ± 0.2 to 22.8 ± 0.3. This method will provide important data for improving our understanding of the role of wet deposition in the biogeochemical cycling of iron.     

Molecular motility and affinity of expanded carbon dioxide + ketone systems analyzed by molecular dynamics simulations

We perform a molecular dynamics simulation for CO₂ + ketone mixtures to study the molecular motility and elucidate how CO₂ molecules are dissolved in a mixture. The self-diffusion coefficients increase with increasing CO₂ mole fraction (xCO₂)$(x_{\text{C}{\text{O}}_2})$ and decreased with increasing molecular weight. These results mean that the mobility of molecules depends on the molecular size. To study molecular aggregation around CO₂ molecules, radial distribution functions (RDFs) and the distance from neighboring molecules to CO₂ molecules were calculated. The RDFs indicate that the CO₂ molecule exists near the carbonyl oxygen atom. Because of the distance of the neighboring molecule from the CO₂ molecule, the CO₂ molecule is less likely to exist around a branched alkyl ketone than a normal alkyl ketone.     

Synthesis and characterization of the azido-bound five-coordinate high-spin iron(II) “picket fence” porphyrin complex

An Fe(II)-azido five-coordinate picket fence porphyrin complex with the formula [Na(2,2,2-crypt)][Fe^II(TpivPP)(N₃)] · 3C₆H₅Cl (TpivPP = α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato, known as a picket fence porphyrin, and 2,2,2-crypt is the cryptand-222) has been synthesized and characterized. The synthesis utilizes cryptand-222 to solubilize sodium azide in the preparation procedure. The UV–Vis and IR spectroscopic data are consistent with an azido ferrous porphyrinate. The X-ray structural analysis and the Mössbauer results indicate that the ion complex [Fe^II(TpivPP)(N₃)]⁻ is high-spin and has the (d_xy)²(d_xz)¹(d_yz)¹(d_z2)¹(d_x2-y2)¹$({\text{d}}_{\mathit{xy}}{)}^2({\text{d}}_{\mathit{xz}}{)}^1({\text{d}}_{\mathit{yz}}{)}^1({\text{d}}_{z^2}{)}^1({\text{d}}_{x^2-y^2}{)}^1$ ground state electronic configuration.     

Modelling LLE and VLE of methanol + n-alkane series using GC-PC-SAFT with a group contribution kij

The fluid phase diagrams (LLE and VLE) of methanol + n-alkane mixtures series (from C₄ up to C₁₆) were modelled using GC-PC-SAFT EOS (Tamouza et al., Fluid Phase Equilibria 222–223 (2004) 67–76) combined with a recent method for computing k_ij based on the London theory (NguyenHuynh et al., Industrial & Engineering Chemistry Research 47 (2008) 8847–8858). This latter method requires pure compound adjustable parameters: pseudo-ionization energies J that may be calculated by group contribution in the case of n-alkane series. J_alkane is calculated from group parameters JCH₃$J_{\text{C}{\text{H}}_3}$ and JCH₂$J_{\text{C}{\text{H}}_2}$.     

Transport properties of protic ionic liquids,pure and in aqueous solutions: Effects of the anion and cation structure

Ionic conductivities of twelve protic ionic liquids (PILs) and their mixtures with water over the whole composition range are reported at 298.15 K and atmospheric pressure. The selected PILs are the pyrrolidinium-based PILs containing nitrate, acetate or formate anions; the formate-based PILs containing diisopropylethylammonium, amilaminium, quinolinium, lutidinium or collidinium cations; and the pyrrolidinium alkylcarboxylates, [Pyrr][C_nH_2n+1COO] with n = 5–8. This study was performed in order to investigate the influence of molecular structures of the ions on the ionic conductivities in aqueous solutions. The ionic conductivities of the aqueous solutions are 2–30 times higher than the conductivities of pure PILs. The maximum in conductivity varies from ww=0.41 ??to ??0.74$w_w=0.41\text{\hspace{0.17em}??}\text{to}\text{\hspace{0.17em}??}0.74$ and is related to the nature of cations and anions. The molar conductance and the molar conductance at infinite dilution for (PIL + water) solutions are then determined. Self-diffusion coefficients of the twelve protic ionic liquids in water at infinite dilution and at 298.15 K are calculated by using the Nernst–Haskell, the original and the modified Wilke–Chang equations. These calculations show that similar values are obtained using the modified Wilke–Chang and the Nernst–Haskell equations. Finally, the effective hydrodynamic (or Stokes) radius of the PILs was determined by using the Stokes–Einstein equation. A linear relationship was established in order to predict this radius as a function of the anion alkyl chain length in the case of the pyrrolidinium alkylcarboxylates PILs.