Study of the Volumetric Properties of the Aqueous Ionic Liquid 1-Methyl-3-pentylimidazolium Tetrafluoroborate

This paper reports the densities of aqueous solutions of the ionic liquid (IL) 1-methyl-3-pentylimidazolium tetrafluoroborate ([pmim][BF₄]) that were measured from 278.15 to 343.15 K, at intervals of 5 K, using an Anton Parr model DMA 4500 oscillating U-tube densitometer. The apparent molar volume, ^φ V _B, and the partial molar volume of [pmim][BF₄], , were calculated. The values of the apparent molar volume, ^φ V _B, were fitted to Pitzer’s model for volumetric properties by the method of least-squares, which allowed the partial molar volume of the IL at infinite dilution, , and Pitzer’s parameters, β _M,X ^(0)V and β _M,X ^(1)V , to be obtained. The small standard deviations of the fits show that Pitzer’s model is also appropriate for representing the volumetric properties of aqueous solutions of the ionic liquid [pmim][BF₄].     

Thermodynamic investigation of room temperature ionic liquid

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF₄) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C _P,m (J K^–1 mol^–1)= 195.55+47.230 X–3.1533 X ²+4.0733 X ³+3.9126 X ⁴ [X=(T–125.5)/45.5] for the solid phase (80~171 K), and C _P,m (J K^–1 mol^–1)= 378.62+43.929 X+16.456 X ²–4.6684 X ³–5.5876 X ⁴ [X=(T–285.5)/104.5] for the liquid phase (181~390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIBF₄ relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass translation of BMIBF₄ was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BMIBF₄ was determined to be Δ_c H _m ^o= – 5335±17 kJ mol^–1. The standard molar enthalpy of formation of BMIBF₄ was evaluated to be Δ_f H _m ^o= –1221.8±4.0 kJ mol^–1 at T=298.150±0.001 K.     

Micellar and associated thermodynamic properties of binary mixtures of alkyl triphenyl phosphonium bromides in ethylene glycol and water mixtures

Micellar properties of binary combinations of a family of cationic alkyl triphenyl phosphonium bromides with varying chain length (C₁₀–C₁₆) were investigated in aqueous and aqueous ethylene glycol mixtures employing conductometric technique. The results of the mixed systems were analyzed in the light of the Regular Solution Theory and the Gibbs–Duhem equation to evaluate the composition of the mixed micelle, the activity coefficients, and the interaction parameter (β). The excess free energy and the other related thermodynamic parameters of mixing were calculated and discussed in terms of the stability of the mixed micelles in the presence of an ethylene glycol additive. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Photosensitive heterojunctions of silicon coated with sol–gel derived TiO2 dispersed in poly(3,4-ethylendi oxythiophene)/poly(styrenesulfonate)

Sol–gel derived aggregates of titania nanocrystals, synthesized starting from alcohol–water solutions of titanium isopropoxide, were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) measurements. The TiO₂ powder was dispersed in aqueous solutions of poly(3,4-ethylendioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS), and the blends were coated on n-doped silicon substrates to achieve simple design heterojunctions. Current versus voltage measurements performed both in the dark and under broad band light irradiation show that the nSi/PEDOT-PSS/TiO₂ heterojunctions have remarkable photosensitive behaviour, promising in view of applications as hybrid photovoltaic cells.     

Electrochemical reactivity of Li–Mn–O and Li–Fe–Mn–O spinels

Electrochemical reductive dissolution of Li–Mn–O and Li–Fe–Mn–O spinels and Li⁺ extraction/insertion in these oxides were performed using voltammetry of microparticles. Both electrochemical reactions are sensitive to the Fe/(Fe+Mn) ratio, specific surface area, Li content in tetrahedral positions, and Mn valence, and can be used for electrochemical analysis of the homogeneity of the elemental and phase composition of synthetic samples. The peak potential (E _P) of the reductive dissolution of the Li–Mn–O spinel is directly proportional to the logarithm of the specific surface area. E _P of Li–Fe–Mn–O spinels is mainly controlled by the Fe/(Fe+Mn) ratio. Li⁺ insertion/extraction can be performed with Mn-rich Li–Fe–Mn–O spinels in aqueous solution under an ambient atmosphere and it is sensitive to the regularity of the spinel structure, in particularly to the amount of Li in tetrahedral positions and the Mn valence. Electronic Publication     

Hybrid Inorganic/Organic Quasi-Single Crystals of Wheel-Shaped \{\hbox{Mo}_{154}\} Macro-anions and Cationic-surfactants

The formation of hybrid inorganic/organic quasi-single crystals from giant polyoxomolybdate (POM) macro-anions in solutions mixed a positively charged surfactant tetradecyltrimethylammonium bromide (TTA⁺Br⁻¹) was described. The crystalline nature of the self-assembled –(TTA)_n complexes was determined by Transmission Electron Microscope (TEM) and Brunauer–Emmett–Teller (BET) analysis. In addition, the quasi-single crystals can further dissolve in aqueous solution with the excess TTABr and the larger hydrophilic aggregations formed. TEM and Dynamic Light Scattering (DLS) investigations were applied to analyze the aggregations in the simple-phase solution.     

Activity coefficients of rubidium chloride and cesium chloride in methanol–water mixtures and a comparative study of Pitzer and Pitzer–Simonson–Clegg models (298.15 K)

Activity coefficients of rubidium chloride and cesium chloride in methanol–water mixed solvent systems were determined by electromotive force (EMF) measurements at 298.15 K, in the range 0–40% (wt.%) methanol. For our work, the cells:

Rb-ISE | RbCl (m), methanol (Y), water (1 − Y) | Cl-ISE;  Cs-ISE | CsCl (m), methanol (Y), water (1 − Y) | Cl-ISE

Ab initio and density functional theory studies on the mechanism of nucleophilic vinylic substitution of 4<Emphasis Type="Italic">H</Emphasis>-pyran-4-one and 2-methyl-4<Emphasis Type="Italic">H</Emphasis>-pyran-4-one with ammonia

 Nucleophilic vinylic substitutions of 4H-pyran-4-one and 2-methyl-4H-pyran-4-one with ammonia were calculated by the B3LYP method using the 6-31G(d,p) basis set. Bulk solvent effects of aqueous solution were estimated by the polarized continuum and Poisson–Boltzmann self-consistent reaction field models using the 6-311+G(d,p) basis set. In the gas phase different mechanisms were found for the two reaction systems calculated. The reaction of 4H-pyran-4-one proceeds through enol, whereas a feasible path for the less reactive 2-methyl-4H-pyran-4-one is the mechanism through a keto intermediate. Addition of ammonia in concert with proton transfer is the rate-determining step ofthe reaction. The mechanism proceeding either by a bimolecular nucleophilic substitution (S_N2) or by one involving a tetrahedral zwitterionic intermediate is shown to be unlikely in the gas phase or nonpolar solution. The effects of bulk solvent not only consist in a reduction of the various activation barriers by about 25–40 kJ mol⁻¹ but also in a change in the reaction mechanism. Received 26 May 2002 / Accepted 26 July 2002 / Published online: 14 February 2003     

Thermodynamics of potassium diclofenac salt aqueous solutions at various temperatures

Solution and dilution enthalpies of aqueous solutions of potassium diclofenac salt (K_DC) were measured by an isoperibolic calorimeter at 298.15 and 318.5 K. Heat capacities of the solutions with concentrations 0.002–0.09 mol kg⁻¹ were obtained at the temperature interval of 288.15–318.15 K using a scanning adiabatic microcalorimeter. The virial coefficients were derived from Pitzer’s model, and the excess thermodynamic functions of both the solvent and the solute of the solution were calculated. The concentration and temperature dependencies of thermodynamic characteristics of the solution were analyzed and discussed.     

Thermo-infrared-spectroscopy analysis of the interaction of naphthylammonium–montmorillonite with sodium nitrite

The deep blue organoclay color pigment (OCCP), naphthylazonaphthylammonium–montmorillonite, was synthesized in an aqueous suspension by treating montmorillonite with naphthylammonium chloride followed after 2 h by NaNO₂. The reddish-brown azo dye naphthylazonaphthylamine (commercial name “Solvent Brown 3”) was synthesized in an aqueous solution in the absence of clay from the same reagents. X-ray diffraction and thermo-infrared (IR) spectroscopy of organoclay prepared by treating montmorillonite with naphthylammonium chloride showed that the organoclay contained two types of tactoids with intercalated naphthylammonium cations and with naphthylammonium–naphthylamine associations. Naphthylammonium clay was obtained after thoroughly washing the latter organoclay. IR spectra of naphthylamine, naphthylammonium chloride, naphthylammonium clay, naphthylammonium–naphthylamine clay (with some naphthylammonium-clay), OCCP, and Solvent Brown 3 in KBr disks were recorded before and after thermal treatments up to 120 °C. IR spectrum of the OCCP was similar to that of Solvent Brown 3. An NH₃ ⁺ group was identified in the spectrum of the OCCP but not in that of Solvent Brown 3. In the latter spectrum, an NH₂ group was identified, suggesting that the amine group of the azo dye in the OCCP was protonated. It appears that the difference in color between OCCP and Solvent Brown 3 resulted from the protonation of the azo molecule in the interlayer space of the clay.     

Pitzer and Pitzer–Simonson–Clegg Modeling Approaches: Ternary HCl + 2-Propanol + Water Electrolyte System

Despite its success for modeling electrolyte thermodynamics in aqueous media, the use of the Pitzer approach for the investigation of electrolytes in nonaqueous or in mixed solvent media is still very limited. Further, a review of the literature reveals that there are no more than a few research groups who have used the exact form of the Pitzer–Simonson–Clegg (PSC) ion-interaction approach for the investigation of electrolytes in mixed solvent systems. As a continuation of our previous studies, the present investigation reports modeling of HCl in the 2-propanol + water mixed solvent system with the Pitzer, PSC and an extended form of the PSC ion-interaction approaches using the experimental potentiometric data from a cell containing pH glass membrane and Ag/AgCl electrodes. The electrochemical measurements were performed over the HCl molality range from 0.01 to 4.5 mol⋅kg⁻¹ in mixed 2-propanol (x%)+water (100−x%) solvents, with different solvent percent mass fractions (x%=10,20,30,40 and 50%) at 298.15±0.05 K.     

Analysis of Solvent–Solvent Interactions in Mixed Isosteric Solvents by Inverse Gas Chromatography

The Flory–Huggins interaction parameter, χ ₂₃, characterizing the interaction between solvents in a mixed stationary phase has been calculated using inverse gas chromatography (IGC). The χ ₂₃ parameters for four mixed solvent systems formed by mixing a non-polar branched alkane, 19, 24-dioctadecyldotetracontane (C78), with four different polar solvents are analysed as a function of temperature. Two of the polar solvents are formed by replacing one of the –CH₃ groups of C78 by –OH (POH) group and –CN (PCN) group and the other two polar solvents are formed by replacing all the four –CH₃ groups of C78 by four –CF₃ (TTF) groups and four –OCH₃ (TMO) groups. The five solvents have similar structures and nearly the same molar volume and in mixtures, they form regular solutions. For the mixture, C78 + POH, χ ₂₃ was calculated at two compositions and for the remaining three mixtures χ ₂₃ was calculated at equimolar composition. Eight solute probes representing all possible chemical structures and polarity were used under conditions approaching infinite dilution. The effects of temperature, concentration of the mixed solvent and probe solute on χ ₂₃ are presented and discussed. The probe-independent χ ₂₃ values were also calculated by linear regression analysis using the retention data of all the solute probes. In all the mixed solvents considered here the χ ₂₃ values are probe-dependent and decrease with increase of temperature.     

Solubility in the ternary system CaSO<Subscript>4</Subscript> + Na<Subscript>2</Subscript>SO<Subscript>4</Subscript> + H<Subscript>2</Subscript>O at 298.15 K

The solubility in the ternary system, aqueous mixture of CaSO₄ and Na₂SO₄, at T = 298.15 K comprises five different salts: calcium sulfate dihydrate, mirabilite, thenardite, glauberite and labile salt. Using the Extended Pitzer’s Ion Interaction model for pure and mixed electrolyte solutions and criteria of phase equilibria, predicted solubility behavior of salts was compared with experimental results from literature. The agreement between calculated and experimental solubilities was excellent in the ionic strength range up to 10.9062 mol kg⁻¹.     

Fundamental aspects of the polarization resistance technique—the early days

The work of Oldham and Mansfeld dealing with the concept of the polarization resistance technique that can be used to determine corrosion rates from potential E—current I curves measured in the vicinity of the corrosion potential E _corr has been summarized. In addressing the interpretation of this technique as the “linear polarization (resistance) technique,” Oldham and Mansfeld pointed out that curvature of polarization curves in the vicinity of E _corr has to occur in order for the Butler–Volmer equation, as modified for corrosion reactions, to be valid. They proposed a modification of the Stern–Geary linear polarization equation and presented a new graphical method for the calculation of corrosion rates from polarization curves. Some of the earliest computer programs for the determination of corrosion current densities, and Tafel slopes from polarization data collected in the vicinity of E _corr and examples of their application have been discussed. Dedicated to the 80th birthday of Keith B. Oldham.     

Method optimization for determination of selected perfluorinated alkylated substances in water samples

In recent years perfluorinated alkylated substances (PFAS) have appeared as a new class of global pollutant. Besides being an industrially important group of compounds, PFAS are regarded as highly toxic and extraordinarily persistent chemicals that pervasively contaminate human blood and wildlife throughout the world. They are therefore regarded as PBT (persistent, bioaccumulative, and toxic) chemicals. Two comprehensive methods have been developed for determination of eleven of the most environmentally relevant PFAS (seven perfluoroalkylcarboxylates, two perfluoroalkylsulfonates, and two perfluoroctanesulfonamides) in aqueous samples. The compounds were isolated by liquid–liquid extraction (LLE) and solid-phase extraction (SPE), and identification and quantification of the target analytes were achieved by liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS–MS). With LLE detection limits ranged from 0.26 to 0.62 ng L⁻¹ for enrichment of 900-mL water samples; recovery of PFAS with a carbon chain longer than C₇ was excellent (80–93%). With SPE, carboxylates with carbon chains <C₁₀ could be extracted efficiently (70–98%) under acidic conditions, and PFOS and PFOSA could be extracted efficiently (81% and 96%, respectively) under basic conditions, resulting in MDLs between 0.25 and 0.64 ng L⁻¹. The LLE method was applied successfully to Austrian wastewater effluent samples.     

Enthalpies of Dilution and Enthalpies of Mixing of Amino Acids with Sucrose in Aqueous Solutions at 298.15 K

The enthalpies of mixing of aqueous solutions have been determined for sucrose with six different amino acids (glycine, l-alanine, l-serine, l-valine, l-proline and l-threonine) at 298.15 K, by using a LKB-2277 flow microcalorimetric system. These results, along with the enthalpies of dilution of these solutes for the initial solutions, were used to determine the enthalpic interaction coefficients (h _xy, h _xyy, h _xxy) of the McMillan–Mayer Theory. The pair-wise cross interaction coefficients of amino acids and sucrose are discussed from the viewpoint of solute–solute interactions.     

Average inner product sums of electron linear momenta for atoms and ions

From the second moments of the electron-pair densities in momentum space, accurate Hartree–Fock values of the average inner product sum 〈∑ _i<j p _i ·p _j 〉 of electron linear momenta are evaluated for the 102 neutral atoms from He to Lr, the 53 singly charged cations from Li⁺ to Cs⁺, and the 43 stable anions from H⁻ to I⁻ in their experimental ground states. The present results are new for 38 species and improve the literature values for 68 species. Received: 18 July 2002 / Accepted: 4 September 2002 / Published online: 8 November 2002 Acknowledgement. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education of Japan. Correspondence to: H. Matsuyama e-mail: hisashi@mmm.muroran-it.ac.jp     

The Effect of Ge,Ni, and Fe Doping on the Ga Activity in the CoGa B2 Phase

Summary. Gallium activity in the B2 (CsCl-type) phase of ternary Co–Ga–X (X = Ge, Ni, and Fe) alloys was measured by the EMF method with a stabilized zirconia solid electrolyte. The temperature range was 1050–1250 K and the concentrations of the added elements were 2–6 at-% Ge and Ni, and 1–3 at-% Fe. The reference electrodes were Fe,Fe_xO or Ga,Ga₂O₃. The effect on the activity of gallium in the B2 phase with the addition of other elements was found to be the largest with Ge and the smallest in the case of Ni.     

Determination of lead in sediments and sewage sludge by on-line hydride-generation axial-view inductively-coupled plasma optical-emission spectrometry using slurry sampling

Among the “traditional” hydride-forming elements, lead is probably the most difficult, and its determination in this form has rarely been reported in the literature. In this paper a simple and rapid method, axial-view inductively-coupled plasma optical-emission spectrometry using on-line hydride generation (HG–ICP–OES) from samples prepared as slurry, is proposed for determination of lead in environmental samples. The samples (20–50 mg, particle size ≤120 μm) were treated with 1 mL aqua regia in a 40-kHz ultrasonic bath for 60 min. The slurry was diluted to a final volume of 50 mL with a 10% m/v solution of (NH₄)₂S₂O₈. The concentrations of NaBH₄, tartaric acid, and (NH₄)₂S₂O₈, used for on-line plumbane generation were optimized by means of a complete factorial analysis applied to an aqueous standard solution and to the slurry of a sediment certified reference material (CRM). External calibration against aqueous standards in the concentration range 10–100 μg L⁻¹ was used for analysis of six CRM—three marine sediments, one river sediment, and two sewage sludges. Analysis of the filtered slurry showed that Pb was only partially extracted into the liquid phase. Several major concomitants tested did not affect the Pb signal. The detection limit (3s, n = 10) for 20 mg sample in a final volume of 50 mL was 5.0 μg g⁻¹. Tin was the only other hydride-forming analyte that could be determined satisfactorily with Pb; for tin the detection limit was 1.0 μg g⁻¹. The values obtained for Pb and Sn were not significantly different from the certified concentrations, according to the t-test at the 95% confidence level. Nine river sediments collected locally were also analyzed and the concentrations were in agreement with results obtained after total digestion.     

Structure and stability of hypervalent NLi n Na2 (n = 1–4) and related species at density functional theory level

A number of configurations of NLi _n Na₂ (n = 1–4) species were optimized using the B3LYP–density functional theory method; the 6-31G^* basis set was used in this calculation. In order to study all possible dissociation energies, some related species such as NLi₂Na, NLi _n (n = 1–4), Li _n (n = 1, 2) and Na _n (n = 1, 2) were also considered. Optimizations of these species were followed by fundamental frequency calculations at the same level. Global minima of these species were shown to adopt C _{2 v} (NLi₄Na₂, NLi₂Na₂), D _{3 h} (NLi₃Na₂) and C _s (NLiNa₂ and NLi₂Na) configurations. All possible dissociation energies were obtained. Received: 30 November 1998 / Accepted: 15 October 1999 / Published online: 14 March 2000