Ionization Constants of Aqueous Glycolic Acid at Temperatures up to 250 <Superscript>∘</Superscript>C Using Hydrothermal pH Indicators and UV-Visible Spectroscopy

Chemical equilibrium constants for the ionization of aqueous glycolic acid (hydroxyacetic acid, HOCH₂COOH) have been measured at temperatures 25–250 ^∘C and pressure p = 4.5 MPa, using UV-visible spectroscopy with a high-pressure flow cell and thermally-stable colorimetric pH indicators. These are the first experimental values for the ionization constant of glycolic acid above 100 ^∘C that have been reported. The results have been combined with recently determined values for the standard partial molar volumes of HOCH₂COOH(aq) and HOCH₂COO⁻(aq) under hydrothermal conditions to develop an “equation of state” that describes the temperature- and pressure-dependence of the equilibrium constant and standard partial molar properties of ionization from 25 to 325 ^∘C.     

A Raman Spectrographic and Potentiometric Study of Aqueous Lithium and Potassium Acetate Complexation at Temperatures from 20 to 200 <Superscript>∘</Superscript>C

The Raman spectra of aqueous NaOH–CH₃COOH solution containing either LiCl or KCl were collected at temperatures from 20 to 200 ^∘C. Interpretation of these spectra reveals significant aqueous LiCH₃COO⁰ formation, but no evidence of aqueous KCH₃COO⁰ formation. LiCH₃COO⁰ dissociation constants generated from these data decrease with the increasing temperature from −0.25 at 20 ^∘C to −1.08 at 200 ^∘C. Potentiometric measurements were performed on similar solutions at temperatures from 25 to 90 ^∘C. These results are in general agreement with the Raman spectral results. Significant aqueous Li-acetate complexing is observed; aqueous K-acetate complexing is far weaker than that of Li-acetate. Dissociation constants for aqueous LiCH₃COO⁰ generated from the potentiometric measurements decrease from −0.20 at 25 ^∘C to −0.62 at 90 ^∘C, whereas those for aqueous KCH₃COO⁰ decrease from ≳ 0.35 to −0.02 over this temperature range.     

Ionic Interactions of Calcium Sulfate Dihydrate in Aqueous Sodium Chloride Solutions: Solubilities,Densities, Viscosities,Electrical Conductivities,and Surface Tensions at 35 <Superscript>∘</Superscript>C

The thermodynamic, volumetric, transport, and surface properties, solubilities, densities, viscosities, electrical conductivities, and surface tensions of calcium sulfate dihydrate in aqueous sodium chloride solutions have been measured at 35 C, with a view to determine the ionic interactions that occur in these solutions. The experimental density values have been used to calculate the mean apparent molar volumes of the ternary mixtures. Viscosity values have been analyzed using different empirical equations and the experimental values of the viscosity were combined with conductivity to yield the Walden product. Molar surface energies have been computed using experimental surface tension data. The experimental data have been fitted to polynomial equations by a least-squares analysis to obtain the coefficients and their standard errors. Results have been examined in the light of structure making or structure breaking effects of the various ions present in the solutions.     

Thermodynamics of Electrolyte Mixtures: HCl + NdCl<Subscript>3</Subscript> + H<Subscript>2</Subscript>O from 5 to 55 <Superscript>∘</Superscript>C

Electromotive-force (emf) measurements of cells containing solutions of hydrochloric acid and neodymium chloride were reported at constant total ionic strengths (I) of 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, and 1.5 mol-kg⁻¹ at 11 temperatures ranging from 5 to 55 ^∘C, and at I = 2.0 mol-kg⁻¹ at 25 ^∘C. Hydrogen and silver–silver chloride electrodes were used in these cells. Results from the emf measurements, the mean molal activity coefficients of HCl in HCl + NdCl₃ + H₂O mixtures, as well as the Harned interaction coefficients using Harned's rule are reported in the preceding article in this issue. The ion-interaction model of Pitzer is applied here for the evaluation of the Pitzer mixing coefficients, ^Sθ_H,Nd and ψ_H,Cl,Nd, as well as the linear representation of the temperature derivatives of ∂^Sθ_H,Nd /∂ T and ∂ψ_H,Nd,Cl/∂T. The activity coefficients at several ionic strength fractions y of NdCl₃ are given at 25 ^∘C. The results are interpreted in terms of ionic interactions.     

Theoretical evaluation of the radiative lifetimes of LiCs and NaCs in the A<Superscript>1</Superscript>Σ<Superscript>+</Superscript> state

Calculations of the adiabatic potential energy curves and the transition dipole moments between the ground (A¹Σ⁺) and the first excited (A¹Σ⁺) states have been determined for the LiCs and NaCs molecules. The calculations are performed using an ab initio approach based on non-empirical pseudopotentials for Cs⁺, Li⁺ and Na⁺ cores, parameterized l-dependent polarization potentials and full configuration interaction calculations. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the A⁺Σ⁺ state using the Franck–Condon (FC) approximation and the approximate sum rule method. The radiative lifetimes associated with the A⁺Σ⁺ state are presented here for the first time. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice.     

Hydrohysteretic Phenomena of “Extremely Diluted Solutions” Induced by Mechanical Treatments: A Calorimetric and Conductometric Study at 25 <Superscript>∘</Superscript>C

The purpose of this study was to obtain information about the influence of successive dilutions and succussions (violent shaking) on the structure of water. “Extremely diluted solutions” (EDS) are solutions obtained through the iteration of two processes: 1:100 dilution and succussion. Those two processes are repeated until extreme dilutions are reached, so that the chemical composition of the end solution is identical to that of the solvent. We measured the heats of mixing and the electrical conductivity of basic solutions of such EDS, and compared these results with the analogous heats of mixing and electrical conductivity of the untreated solvent. The measurements were carried out as a function of the age of the samples. We found some relevant exothermic excess heat of mixing, and higher electrical conductivity than those of the untreated solvent, also in function of time. The measurements show a good linear correlation between the two independent physico-chemical quantities, implying a single cause for this behavior of the extremely diluted solutions. The slopes of the linear correlation depend on the age of the EDS. Such a phenomenon could result from a variation of the shape of molecular aggregates that characterize the two different supramolecular structures of the water of different ages. This behavior could provide important support for understanding the nature of the phenomena described herein. A really intriguing phenomenon is the evolution of some physico-chemical properties with time. This hints at a “trigger” effect on the formation of molecular aggregates that result from the succussion procedure. We show that successive dilutions and succussions can permanently alter the physico-chemical properties of the aqueous solvent, the extent of which depends on the age of the samples.     

Effects of substituents in the cationic and anionic η<Superscript>3</Superscript>-allylpalladium complexes according to data from <Superscript>13</Superscript>C NMR spectroscopy and quantum chemical calculations

A linear correlation of chemical shifts (δ) of signals in the ¹³C NMR spectra of the unsubstituted terminal carbon atom of the allyl ligand in [(1-R-η³-C₃H₄)Pd]NO₃ (R = Me, CH₂OMe, CO₂Me, COMe, CHO) with the substituent constants σ⁺ and σ^s- in acetone solutions was found. A considerable deviation from linearity was observed for R = Ph. The ¹³C nuclear magnetic screening constants were calculated by the DFT method in the GIAO approximation for equilibrium geometries of the cations [(1-R-η³-C₃H₄)Pd(Me₂C=0)₂]⁺ and anions [(1-R-η³-C₃H₄)PdCl₂]^s-. In the latter case, the theoretical and experimental δ values are consistent. The influence of the substituent R on the geometric parameters and charges on atoms in the neutral, anionic, and cationic η³-allylpalladium complexes is discussed.     

<Superscript>13</Superscript>C-labeled bilirubin: synthesis of 3<Superscript>1</Superscript>(3<Superscript>2</Superscript>),17<Superscript>1</Superscript>(17<Superscript>2</Superscript>)-di-[<Superscript>13</Superscript>C]-mesobilirubin-XIIIα

Abstract  The title compound, labeled with ¹³C in the ethyl groups was synthesized from K¹³CN and low-molecular-weight components. The synthetic relay compound was 3¹(3²)[¹³C]-xanthobilirubinic acid methyl ester in a synthetic route that leads to a label in the ethyl β-substituent of a dipyrrinone model for bilirubin. This labeled dipyrrinone was oxidatively coupled to the dimethyl ester of mesobiliverdin-XIIIα, thereby providing a route to a ¹³C-labeled mesobiliverdin and mesobilirubin, with one carbon of each ethyl being 98% ¹³C-enriched. Graphical Abstract        

Ultrasonic and Raman Scattering Spectroscopy of Zinc Thiocyanate Complexes in Water at 25<Superscript>∘</Superscript>C: Kinetics of Complex Formation Determined by Multivariate Analysis

Advances have been made recently in broadening the accessible ultrasonic absorption frequency range and improving the detectability of minor species present in solution using Raman spectroscopy. Development of chemometric techniques in these areas needs to keep pace with the improvement of these experimental methods. Refinements in the analysis of ultrasonic and Raman data based on multivariable least squares and factor analysis, respectively, are examined to investigate the kinetics of zinc thiocyanate complex formation in water. Analysis of ultrasonic absorption relaxation spectra verified that the observed process in aqueous Zn(SCN)₂ involves substitution of water from the first coordination shell of Zn²⁺. Use of a multivariable least-squares error surface is described that enhances the reliability of assigned frequencies of ultrasonic absorption maxima. Factor analysis of Raman scattering data provided direct evidence that at least four complex species, such as Zn(SCN)⁺ and Zn(SCN)₂, are simultaneously present in the aqueous zinc thiocyanate solutions.     

Re-evaluation of the Activity Coefficients of Aqueous Hydrochloric Acid Solutions up to a Molality of 16.0 mol·kg<Superscript>−1</Superscript> Using the Hückel and Pitzer Equations at Temperatures from 0 to 50 °C

The simple three-parameter Pitzer and extended Hückel equations were used for calculation of activity coefficients of aqueous hydrochloric acid at various temperatures from 0 to 50 °C up to a molality of 5.0 mol·kg^?1. A more complex Hückel equation was also used at these temperatures up to a HCl molality of 16 mol·kg^?1. The literature data measured by Harned and Ehlers J. Am. Chem. Soc. 54, 1350–1357 (1932) and 55, 2179–2193 (1933) and by Åkerlöf and Teare [J. Am. Chem. Soc. 59, 1855–1868 (1937)] on galvanic cells without a liquid junction were used in the parameter estimations for these equations. The latter data consist of sets of measurements in the temperature range 0 to 50 °C at intervals of 10 °C, and data at these temperatures were used in all of these estimations. It was observed that the estimated parameters follow very simple equations with respect to temperature. They are either constant or depend linearly on the temperature. The values for the activity coefficient parameters calculated by using these simple equations are recommended here. The suggested new parameter values were tested with all reliable cell potential and vapor pressure data available in literature for concentrated HCl solutions. New Harned cell data at 5, 15, 25, 35, and 45 °C up to a molality of 6.5 mol·kg^?1 are reported and were also used in the tests. The activity coefficients obtained from the new equations were compared to those calculated by using the Pitzer equations of Holmes et al. [J. Chem. Thermodyn. 19, 863–890 (1987)] and of Saluja et al. [Can. J. Chem. 64, 1328–1335 (1986)] at various temperatures, and by using the extended Hückel equation of Hamer and Wu [J. Phys. Chem. Ref. Data 1, 1047–1099 (1972)] at 25 °C.     

Molecular Interactions in Propylene Carbonate + <Emphasis Type="Italic">n</Emphasis>-Alkanols at 25 <Superscript>∘</Superscript>C

Densities and viscosities of the binary mixtures of propylene carbonate with methanol, ethanol, propanol, butanol, and hexanol, along with those of the pure liquids, were measured over the entire mole fraction range at 25 C. Using the experimental values of densities and viscosities , the excess molar volumes V^E, viscosity deviations , excess Gibbs energies of activation of viscous flow G^E, and Grunberg–Nissan interaction parameters d₁₂ were calculated from the linear dependence of these parameters on the composition of the mixtures.     

Variation of <Superscript>231</Superscript>Pa, <Superscript>230</Superscript>Th and <Superscript>231</Superscript>Pa<Subscript>ex</Subscript>/<Superscript>230</Superscript>Th<Subscript>ex</Subscript> in surface sediments of the Sabah–Sarawak coastal waters

Protactinium and thorium activities were measured in eight surface sediment taken in 2004 to determine effectiveness scavenging of ²³¹Pa at Sabah–Sarawak coastal waters. The result found that activity ratios of ²³¹Pa_ex/²³⁰Th_ex were ranged from 0.07 to 0.13 at all sampling stations. The high ²³¹Pa_ex/²³⁰Th_ex activity ratio than the production ratio of 0.093 in seawater at station SR 01, SR 02, SR 04, SB 02 and SB 05, revealed that ²³¹Pa is effectively removed from the water column into the sediment in comparison with ²³⁰Th at those stations. Low percentage of ²³⁰Th_ex (90–95%) in comparison with ²³¹Pa_ex at all stations can be attributed to less efficiently scavenged of ²³⁰Th onto particles prior deposited at the marine sediment bed.     

Validation of <Superscript>90</Superscript>Sr separation method using molecular recognition product AnaLig<Superscript>®</Superscript> Sr01 gel and extraction chromatography Sr<Superscript>®</Superscript> resin

Two separation techniques for strontium determination using AnaLig^® Sr01 molecular recognition technology and extraction chromatography Sr^®  resin were tested. The methods performance was investigated by analysis of NPL (High Alpha–Beta 2003) intercomparison sample. The results obtained for both procedures were compared in terms of activities and recoveries. Data analysis proved a good agreement with the reference values. The AnaLig^® Sr01 separation method for ⁹⁰Sr determination was successfully validated with the same performance as the Sr^® resin method.     

The undecahydrodecaborate anion B<Subscript>10</Subscript>H<Stack><Subscript>11</Subscript><Superscript>−</Superscript></Stack> as the starting reagent in exopolyhedral substitution and complexation: Theoretical and experimental prerequisites

Using the electron density functional theory (B3LYP approximation) with the 6-31G* basis set, the potential energy surface of the undecahydrodecaborate anion B₁₀H₁₁⁻ was calculated and the activation energies and the activation barriers for the elementary reactions of proton H* migration around the boron polyhedron were estimated. Analysis of the calculation results in comparison with the experimental data accumulated recently implies that the salts of the B₁₀H₁₁⁻ anion represent a new type of starting compounds for exopolyhedral substitution and complexation involving decaborate anions. Of particular interest is the targeted preparation of isomers of metal complexes containing a decaborate anion depending on the use of B₁₀H₁₀²⁻ or B₁₀H₁₁^¨- as the starting reagent. Certain trends in the reactivity of B₁₀H₁₀⁻ and B₁₀H₁₁⁻ anions can be explained in terms of the simple analysis of Mulliken charge distribution on atoms.     

Characterization and application of SuperLig<Superscript>®</Superscript> 620 solid phase extraction resin for automated process monitoring of <Superscript>90</Superscript>Sr

Characterization of SuperLig^® 620 solid phase extraction resin was performed in order to develop an automated on-line process monitor for ⁹⁰Sr. The main focus was on strontium separation from barium, with the goal of developing an automated separation process for ⁹⁰Sr in high-level wastes. High-level waste contains significant ¹³⁷Cs activity, of which ^137mBa is of great concern as an interference to the quantification of strontium. In addition barium, yttrium and plutonium were studied as potential interferences to strontium uptake and detection. A number of complexants were studied in a series of batch K_d experiments, as SuperLig^® 620 was not previously known to elute strontium in typical mineral acids. The optimal separation was found using a 2 M nitric acid load solution with a strontium elution step of ~0.49 M ammonium citrate and a barium elution step of ~1.8 M ammonium citrate. ⁹⁰Sr quantification of Hanford high-level tank waste was performed on a sequential injection analysis microfluidics system coupled to a flow-cell detector. The results of the on-line procedure are compared to standard radiochemical techniques in this paper.     

Comparative study of Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> ions adsorption from dimethyl formamide at Hg- and Ga-electrodes

The adsorption of Cl⁻, Br⁻, and I⁻ ions from their 0.1 M solutions in dimethyl formamide at renewable liquid Hg- and Ga-electrodes was studied under similar experimental conditions by the differential-capacitance and jet-electrode methods. The data obtained points out to a strong effect of the metal nature on adsorption parameters and the halogenide-ion surface activity series. The halogenide-ion surface activity at the Hg-electrode increased in the following sequence: Cl⁻ < Br⁻ < I⁻; at the Ga-electrode, in the reverse sequence: I⁻ < Br⁻ < Cl⁻. The results are explained qualitatively in terms of the Andersen-Bockris model. It follows from the obtained data that (1) the free energy of the metal-halogenide-ion interaction increases in the following sequence: I⁻ < Br⁻ < Cl⁻; (2) the free energy of the Ga-halogenide-ion interaction exceeds that of the Hg⁻halogenide-ion interaction; and (3) the difference of the Cl⁻, Br⁻, and I⁻ ions interaction with the metals increased significantly when passing from Hg⁻ to Ga-electrode.     

Comparison study of adsorption of Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> ions from dimethyl formamide on In-Ga and Tl-Ga electrodes

The adsorption of Cl⁻, Br⁻, and I⁻ ions on the renewable liquid In-Ga and Tl-Ga electrodes from 0.1 M solutions in dimethyl formamide (DMF) is investigated by using the method of differential capacitance measurements. The results are compared with similar data obtained on Hg and Ga electrodes in DMF and with the corresponding data obtained in acetonitrile (AN). It is shown that, in DMF, the adsorption parameters and the series of surface activity of halide ions (Hal⁻) significantly depend on the metal nature. In contrast to Hg electrode, on which the surface activity of halide ions increases in the series: Cl⁻ < Br⁻ < I⁻, on In-Ga, as well as on the Ga electrode, it varies in the reverse order: I⁻ < Br⁻ < Cl⁻, whereas on the Tl-Ga electrode, partially reversed series of surface activity is observed: Br⁻ < I⁻ < Cl⁻. The results are explained within the framework of Andersen-Bockris model. An analysis of experimental results leads to the following qualitative conclusions: (1) on the In-Ga and Tl-Ga electrodes, as well as on Ga electrode, free energy of metal-Hal⁻ interaction ( $ \Delta G_{_{M - Hal^ - } } $ \Delta G_{_{M - Hal^ - } } ) increases in series I⁻ < Br⁻ < Cl⁻; (2) for Cl⁻, Br⁻, and I⁻, $ \Delta G_{_{M - Hal^ - } } $ \Delta G_{_{M - Hal^ - } } ) grows in series Tl-Ga < In-Ga < Ga; (3) an absolute magnitude of $ \Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } } $ \Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } } (Hal₁⁻, and Hal₂⁻ are any ions of Cl⁻, Br⁻, and I⁻) increases in series Hg < Tl-Ga < In-Ga < Ga; (4) the metal-DMF chemisorption interaction is much stronger than the metal-AN interaction and increases in series Tl-Ga < In-Ga < Ga.     

Consistent transfer of protons in molecular rings of water: Origination of H<Subscript>3</Subscript>O<Superscript>+</Superscript> and OH<Superscript>–</Superscript> ions

For the first time, nonempirical modeling of water clusters composed of several fused molecular rings supplemented with the theoretical analysis of quantum states of the systems provided grounds for clarifying the conditions when consistent shifts of bridge protons within one structural ring promoted by the contraction of the oxygen skeleton can repeatedly cause the formation of H₃O⁺ and OH^– ions.     

Interactions between AuCl<Subscript>4</Subscript><Superscript>−</Superscript> and CTA<Superscript>+</Superscript> ions in water

The solubility of hexadecyltrimethylammonium tetrachloroaurate (CTA·AuCl₄) in water was measured at different temperatures of 288.2, 293.2, 298.2, 303.2, and 308.2 K. The enthalpy change associated with the formation of the CTA·AuCl₄ precipitate was estimated on the basis of the van’t Hoff equation and was found to be −42.5 ± 2.8 kJ mol⁻¹ at 298.2 K. The calorimetric enthalpy change for the CTA·AuCl₄ precipitate formation was directly determined by isothermal titration calorimetry performed at 298.2 K and was found to agree well with that estimated from the van’t Hoff equation.