Temperature and concentration dependences of density and refraction of aqueous duloxetine solutions

Present paper reports the measured densities (ρ) and refractive indices (n _D) of aqueous solutions of Duloxetine drug in wide range of molal concentrations (m = 0.0101–0.1031 mol kg^?1) and at different temperatures (297.15, 302.15, and 307.15 K). Apparent molar volumes (φ_v) of drug were calculated from density data and fitted to Masson’s relation \((\phi _\nu = \phi _\nu ^0 + S_\nu ^* \sqrt c )\) and partial molar volumes (φ _v ⁰ ) were evaluated at different temperatures. Concentration dependence of refractive index (n _D = Kc + n _D ⁰ ) at experimental temperature has been studied. Density and refractive index data has been used for the calculation of specific refractions (R _D). Experimental (ρ and n _D) and calculated (φ_v, φ _v ⁰ , and R _D) properties have been interpreted in terms of concentration and temperature effects on structural fittings and drug-water interactions.     

Thermodynamics of Selected Aqueous Rare-Earth Elements Containing Triflate Salts at T=(288.15, 298.15, 313.15 and 328.15) K and p=0.1 MPa

Aqueous acidified solutions of the rare-earth-element (REE) triflates (Gd(CF₃SO₃)_3(aq), Dy(CF₃SO₃)_3(aq), Nd(CF₃SO₃)_3(aq), Er(CF₃SO₃)_3(aq), Yb(CF₃SO₃)_3(aq) and Y(CF₃SO₃)_3(aq)) have been prepared by the dissolution of the corresponding REE oxides in dilute aqueous trifluoromethanesulfonic acid (triflic acid, CF₃SO₃H_(aq)). Relative densities and relative massic heat capacities have been measured for these systems over the approximate ionic strength range 0.10≤I/(mol?kg^?1)≤1.35 at T=(288.15, 298.15, 313.15 and 328.15) K and p=0.1 MPa. These measurements were completed using a Sodev O2D vibrating tube densimeter and Picker-flow microcalorimeter, respectively. Relative densities and relative massic heat capacities for aqueous solutions of triflic acid and its sodium salt have also been measured over the concentration range 0.018≤m ₂/(mol?kg^?1)≤0.23 over the same temperature range at p=0.1 MPa. Young’s rule has been used to calculate apparent molar volumes and apparent molar heat capacities of the aqueous solutions of REE triflate salts from the calculated apparent molar properties of the acidified salt solutions. These properties have been modeled using the Pitzer ion-interaction equations. The apparent molar properties of aqueous triflic acid solutions and aqueous solutions of its sodium salt have also been modeled using the same Pitzer ion-interaction equations. The apparent molar properties at infinite dilution obtained from our property modeling have been used to calculate single ion volumes and single ion heat capacities for each of the aqueous ions; Gd _(aq) ³⁺ , Dy _(aq) ³⁺ , Nd _(aq) ³⁺ , Er _(aq) ³⁺ , Yb _(aq) ³⁺ , and Y _(aq) ³⁺ . The reported single ion values have been compared with those previously reported in the literature.     

Determination of nitrite, nitrate, bromide, and iodide in seawater by ion chromatography with UV detection using dilauryldimethylammonium-coated monolithic ODS columns and sodium chloride as an eluent

A method was developed for determination of inorganic anions, including nitrite (NO ₂ ^? ), nitrate (NO ₃ ^? ), bromide (Br^?), and iodide (I^?), in seawater by ion chromatography (IC). The IC system used two dilauryldimethylammonium bromide (DDAB)-coated monolithic ODS columns (50?×?4.6?mm i.d. and 100?×?4.6?mm i.d.) connected in series for separation of the ions. Aqueous NaCl (0.5?mol/L; flow rate, 3?mL/min) containing 5?mmol/L phosphate buffer (pH 5) was used as the eluent, and detection was with a UV detector at 225?nm. The monolithic ODS columns were coated and equilibrated with a 1-mmol/L DDAB solution (in H₂O/methanol, 90:10 v/v). The hydrophilic ions (NO ₂ ^? , NO ₃ ^? , and Br^?) were separated within 3?min and the retention time of I^? was 16?min. No interferences from matrix ions, such as chloride and sulfate ions, were observed in 35?‰ artificial seawater. The detection limits were 0.6?μg/L for NO ₂ ^? , 1.1?μg/L for NO ₃ ^? , 70?μg/L for Br^?, and 1.6?μg/L for I^? with a 200-μL sample injection. The performance of the coated columns was maintained without addition of DDAB in the eluent. The IC system was successfully applied to real seawater samples with recovery rates of 94–108?% for all ions.

Hexadecyltrimethylammonium bromide micellization in glycine,diglycine, and triglycine aqueous solutions as a function of surfactant concentration and temperatures

Micellization behavior of hexadecyltrimethylammonium bromide (HTAB) was investigated conductometrically in aqueous solutions containing 0.02 mol kg^?1glycine (Gly), diglycine (Gly-Gly), and triglycine (Gly-Gly-Gly) as a function of surfactant concentration at different temperatures. The critical micelle concentration (CMC) of HTAB exhibits a decreasing trend as the number of carbon atoms increases from Gly to Gly-Gly-Gly, favoring the micelle formation. The values of CMC and the degree of counterion dissociation of the micelles were utilized to evaluate the standard free energy for transferring the surfactant hydrophobic chain out of the solvent to the interior of the micelle, ΔG _HP ^○ , free energy associated with the surface contributions, ΔG _S ^○ , standard free energy, ΔG _m ^○ , enthalpy, ΔH _m ^○ , and entropy, ΔS _m ^○ of micellization were also calculated. The results show that the micellization of HTAB in aqueous solutions as well as in aqueous Gly/Gly-Gly/Gly-Gly-Gly solutions is primarily governed by the entropy gain due to the transfer of the hydrophobic groups of the surfactant from the solvent to the interior part of the micelle. The CMC obtained by fluorometric method is in close agreement with those obtained conductometrically. Furthermore, decrease in the I ₁/I ₃ ratio of pyrene fluorescence intensity suggests the solubilization of the additives by the surfactant micelles and that this solubilization increases as the hydrophobicity increases from Gly to Gly-Gly-Gly.     

The densities and viscosities of aqueous solutions of glycine and glycylglycine containing carbohydrates and structural properties of the ternary systems

Apparent molar volumes, V _? for glycine (Gly) and glycylglycine (Gly-Gly) in aqueous D(+)-glucose and sucrose solutions have been determined from solution density, ρ measurements at 298.15, 303.15, 308.15, and 313.15 K as a function of the concentration of solutes (Gly and Gly-Gly). The standard partial molar volume, V _? ⁰ , transfer volume, ΔV _?(tr) ⁰ , for Gly and Gly-Gly from water to aqueous carbohydrate solutions, partial molar expansibility, E _? ⁰ , and hydration number, n _H of solute have been calculated. The viscosity data have been analyzed by means of Jones-Dole equation to obtain A- and B-coefficients, free energy of activation of viscous flow per mole of solvent, Δμ ₁ ^0# , and solute, Δμ ₂ ^0# , enthalpy, ΔH ^0#, and entropy of activation, ΔS ^0# of viscous flow were evaluated. The behavior of these parameters has been interpreted in terms of solute-solute and solute-solvent interactions.     

The Standard Chemical-Thermodynamic Properties of Phosphorus and Some of its Key Compounds and Aqueous Species: An Evaluation of Differences between the Previous Recommendations of NBS/NIST and CODATA

The aqueous chemistry of phosphorus is dominated by P(V), which under typical environmental conditions (and depending on pH and concentration) can be present as the orthophosphate species H₃PO ₄ ⁰ (aq),H₂PO ₄ ^? (aq),HPO ₄ ^2? (aq) or PO ₄ ^3? (aq). Many divalent, trivalent and tetravalent metal ions form sparingly soluble orthophosphate phases that, depending on the solution pH and concentrations of phosphate and metal ions, can be solubility limiting phases. Geochemical and chemical engineering modeling of solubilities and speciation require comprehensive thermodynamic databases that include the standard thermodynamic properties for the aqueous species and solid compounds. The most widely used sources for standard thermodynamic properties are the NBS (now NIST) Tables (from 1982 and earlier, with a 1989 erratum) and the final CODATA evaluation (1989). However, a comparison of the reported enthalpies of formation and Gibbs energies of formation for key phosphate compounds and aqueous species, especially H₂PO ₄ ^? (aq) and HPO ₄ ^2? (aq), shows a systematic and nearly constant difference of 6.3 to 6.9 kJ?mol^?1 per phosphorus atom between these two evaluations. The existing literature contains numerous studies (including major data summaries) that are based on one or the other of these evaluations. In this report we examine and identify the origin of this difference and conclude that the CODATA evaluation is more reliable. Values of the standard entropies of the H₂PO ₄ ^? (aq) and HPO ₄ ^2? (aq) ions at 298.15 K and p?° =1 bar were re-examined in the light of more recent information and data not considered in the CODATA review, and a slightly different value of S _m ^o (H₂PO ₄ ^? , aq, 298.15 K) = (90.6±1.5) J?K^?1?mol^?1 was obtained.     

Volumetric Investigations on Interactions of Acidic/Basic Amino Acids with Sodium Acetate, Sodium Propionate and Sodium Butyrate in Aqueous Solutions

The apparent molar volumes, V _φ , of L-aspartic acid, L-glutamic acid, L-lysine monohydrate and L-arginine in water and in aqueous (0.1, 0.25, 0.5 and 1.0) mol?kg^?1 sodium acetate and sodium propionate, and (0.1, 0.25 and 0.5) mol?kg^?1 sodium butyrate solutions have been determined at 288.15, 298.15, 308.15 and 318.15 K from density measurements. The partial molar volumes at infinite dilution, V ₂ ^o , obtained from V _φ data, have been used to calculate hydration numbers and partial molar expansibilities of amino acids in water and in the presence of the studied cosolutes at different temperatures. These parameters have been discussed in terms of various interactions between the acidic/basic amino acids and organic salts in these solutions. The effect of the hydrophobic chain length of the carboxylate ions has also been discussed.     

The Oxidation of Iron(II) with Oxygen in NaCl Brines

The oxidation of nanomolar levels of iron(II) with oxygen has been studied in NaCl solutions as a function of temperature (0 to 50?°C), ionic strength (0.7 to 5.6 mol?kg^?1), pH (6 to 8) and concentration of added NaHCO₃ (0 to 10 mmol?kg^?1). The results have been fitted to the overall rate equation: $$\mathrm{d}\mbox{[Fe(II)]}/\mathrm{d}t=-k_{\mathrm{app}}\mbox{[Fe(II)]}[\mbox{O}_{2}]$$ The values of k _app have been examined in terms of the Fe(II) complexes with OH^? and CO ₃ ^2? . The overall rate constants are given by: $$k_{\mathrm{app}}=\alpha_{\mathrm{Fe}2+}k_{\mathrm{Fe}}+\alpha_{\mathrm{Fe(OH)}+}k_{\mathrm{Fe(OH)}+}+\alpha_{\mathrm{Fe(OH)}2}k_{\mathrm{Fe(OH)}2}+\alpha_{\mathrm{Fe(CO3)}2}k_{\mathrm{Fe(CO3)}2}$$ where α _i is the molar fraction and k _i is the rate constant of species i. The individual rate constants for the species of Fe(II) interacting with OH^? and CO ₃ ^2? have been fitted by equations of the form: $$\begin{array}{l}\ln k_{\mathrm{Fe}2+}=21.0+0.4I^{0.5}-5562/T\\[6pt]\ln k_{\mathrm{FeOH}}=17.1+1.5I^{0.5}-2608/T\\[6pt]\ln k_{\mathrm{Fe(OH)}2}=-6.3-0.6I^{0.5}+6211/T\\[6pt]\ln k_{\mathrm{Fe(CO3)}2}=31.4+5.6I^{0.5}-6698/T\end{array}$$ These individual rate constants can be used to estimate the rates of oxidation of Fe(II) over a large range of temperatures (0 to 50?°C) in NaCl brines (I=0 to 6 mol?kg^?1) with different levels of OH^? and CO ₃ ^2? .     

Extraction of pertechnetate by triphenyltin chloride and trioctyltin chloride

The extraction of pertechnetate in form of ionogene associates with triphenyltin and trioctyltin cations into chloroform, benzene, toluene and nitrobenzene was studied. As aqucous phases solutions of^99mTcO ₄ ^? in deionized water and in diluted solutions of NaCl, HCl, NaNO₃, HNO₃ NaClO₄, HClO₄ and NaOH were used. Concerning the organic phases, at the use of triphenyltin chloride the extractibility of pertechnetate increases in the sequence: toluene «chloroform, benzene nitrobenzene and approximately in the sequence: NaOH<NaCl, HCl<NaNO₃<H₂O<NaClO₄ concerning aqueous phases. For trioctyltin chloride in chloroform the extractibility of TcO ₄ ^? increases approximately in the sequence of aqueous phases: NaOH<HCl, NaNO₃, NaClO₄, NaCl«H₂O and in nitobenzene in the sequence NaOH<NaClO₄<HCl<NaNO₃, NaCl«H₂O. The extractibility for trioctyltin chloride is in general slightly lower as compared with triphenyltin chloride. The results of the extraction are presented in the form of graphical plots of technetium distribution ratio (D _Te′ logD _Tc) or extraction yield (E _Tc, %) against concentration of the investigated component in aqueous or organic phase. In some of the systems of the systems studied practically quantitative extraction of pertechnetate into organic phase has been achieved.     

The enthalpies of solution and solvation of glycine in mixed water-formamide solvents at 298.15 K

The enthalpies of solution (ΔH _sol ^o ) of glycine in aqueous formamide, N-methylformamide, N,N-dimethylformamide, and N,N-diethylformamide were determined by calorimetry at 298.15 K over the concentration range x ₂=0–0.3 mole fractions. The enthalpies of glycine solvation (ΔH _solv ^o ) and transfer from water to mixed solvents (ΔH _tr ^o ) were calculated. The ΔH _sol ^o =f(x ₂) dependences for glycine in water-N-and water-N,N-substituted amide mixtures had extrema and, in water-formamide mixtures, this dependence was a smooth function, whose values changed in the opposite direction. The enthalpy coefficients of pair glycine-amide interactions were calculated. The interrelation between the enthalpy characteristics of solution, transfer, and solvation of glycine and the structure and physicochemical characteristics of solvents, on the one hand, and the composition of mixtures, on the other, was revealed.     

Isopiestic Determination of the Osmotic and Activity Coefficients of Li2SO4(aq) at T=298.15 and 323.15 K, and Representation with an Extended Ion-Interaction (Pitzer) Model

Isopiestic vapor-pressure measurements were made for Li₂SO₄(aq) from 0.1069 to 2.8190 mol?kg^?1 at 298.15 K, and from 0.1148 to 2.7969 mol?kg^?1 at 323.15 K, with NaCl(aq) as the reference standard. Published thermodynamic data for this system were reviewed, recalculated for consistency, and critically assessed. The present results and the more reliable published results were used to evaluate the parameters of an extended version of Pitzer’s ion-interaction model with an ionic-strength dependent third-virial coefficient, as well as those of the standard Pitzer model, for the osmotic and activity coefficients at both temperatures. Published enthalpies of dilution at 298.15 K were also analyzed to yield the parameters of the ion-interaction models for the relative apparent molar enthalpies of dilution. The resulting models at 298.15 K are valid to the saturated solution molality of the thermodynamically stable phase Li₂SO₄?H₂O(cr). Solubilities of Li₂SO₄?H₂O(cr) at 298.15 K were assessed and the selected value of m(sat.)=3.13±0.04 mol?kg^?1 was used to evaluate the thermodynamic solubility product K _s(Li₂SO₄?H₂O, cr, 298.15 K) = (2.62±0.19) and a CODATA-compatible standard molar Gibbs energy of formation Δ_f G _m ^o (Li₂SO₄?H₂O, cr, 298.15 K) = ?(1564.6±0.5) kJ?mol^?1.     

The Mixing Enthalpy Interaction Coefficients of N,N′-Hexamethylenebisacetamide with l-Alanine and l-Serine in Aqueous Glucose Solutions at 298.15 K

The mixing enthalpies of N,N??-hexamethylenebisacetamide (HMBA) with l-alanine and l-serine in aqueous glucose solutions have been determined by using mixing-flow isothermal microcalorimetry along with their dilution enthalpies at the temperature of 298.15?K. These results can be used to obtain the heterotactic enthalpic interaction coefficients (h _xy , h _xxy , and h _xyy ) in the range of the glucose molality, (0 to 1.5) mol?kg^?1, according to the McMillan?CMayer theory. Combining our previous research results for glycine (see Liu et al. in J. Chem. Eng. Data 55, 5258?C5263, 2010), we find that the heterotactic enthalpic pairwise interaction coefficients h _xy between HMBA and the investigated amino acids in aqueous glucose solutions are all positive and reach maximum values at about 0.3 mol?kg^?1 glucose. In addition, the order for the value of h _xy of the three amino acids in pure water and aqueous solution of the same glucose molality is h _xy (l-alanine)>h _xy (l-serine)>h _xy (glycine). All variations of the heterotactic enthalpic pairwise interaction coefficients with the molalities of glucose in the quaternary systems are discussed in terms of solute?Csolute and solute?Csolvent interactions.     

Amino acid hydration in aqueous ammoniu chloride and sodium chloride solutions

Partial volumes $\bar V^0$ of amino acids in aqueous NH₄Cl and NaCl solutions are discussed. The salts have different effects on water structure. The contributions of the charged NH ₃ ⁺ and COO^? groups of amino acids are found. Structural characteristics of hydrated complexes are calculated: partial volumes of water inside and outside the hydration sphere and hydration numbers. The same value of $\bar V^0$ (NH ₃ ⁺ , COO^?) is achieved at a higher NH₄Cl concentration. The two salt systems with the same $\bar V^0$ (NH ₃ ⁺ , COO^?) have similar values of the partial volumes of water and hydration numbers.     

Critical micelle concentration and self-aggregation of hexadecyltrimethylammonium bromide in aqueous glycine and glycylglycine solutions at different temperatures

Conductivities, densities and ultrasonic speeds measurements of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions of glycine (Gly) and glycylglycine (Gly-Gly) have been made at various temperatures. The critical micelle concentration (CMC), the degree of ionization (??) of the micelles, standard free energy, enthalpy, and entropy of the micellization process (??G _m ^° , ??H _m ^° , and ??S _m ^° ) for the present systems were estimated at different temperatures. The CMC values of HTAB in aqueous Gly and Gly-Gly were also evaluated by density and ultrasonic speed measurements. Apparent molar volumes, (V _?), apparent molar volumes at infinite dilution, (V _? ^° ), apparent molar compressibilities, (K _?), of HTAB in the pre- and post-micellar regions, and volume change on micellization (??V _? ^m ) were also estimated. Large positive values of T??S _m ^° and small negative values of ??H _m ^° suggest that micellization process is driven primarily by entropy increase. The increase in ??V _? ^m and K _? with rise in temperature is indicative of less compact micellar structure of HTAB in presence of amino acid additives. These data suggest that amino acids are solubilised probably in the palisade layer of the micelle.     

The electronic structure of FeO 4 2− , RuO4, RuO 4 − , RuO 4 2− and OsO4 by the HFS-DVM method

The electronic structures of FeO ₄ ^2? , RuO₄, RuO ₄ ^? , RuO ₄ ^2? and OsO₄ have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals is 2t ₂, 1e, 2a ₁, 3t ₂ andt ₁ with thet ₁ orbital as the highest occupied. The first five charge transfer bands are assigned as:t ₁→2e(v ₁), 3t ₂→2e(v ₂),t ₁→4t ₂(v ₃), 3t ₂→4t ₂(v ₄) and 2a ₁→4t ₂(v ₅). It is suggested that ad-d transition should be observed at 1.5 eV in RuO ₄ ^? and RuO ₄ ^2? .     

Mathermatical modeling of equilibria and the state of holmium heteropoly tungstate ions

The interaction in the HoW₁₀O ₃₆ ^9? -H⁺-OH^?-H₂O system is studied using pH titration at cH0W₁₀O ₃₆ ^9? = 10^?3 mol/l in various base electrolytes (NaNO₃, NaCl, Na₂SO₄). The pH titration data are used to simulate the processes in the solution in ranges of z _H ⁺ = 0?6.5 and z _OH ⁺ = (?4)-0. The concentration and thermodynamic equilibrium constants are calculated, and heteropolytungstate anion (HPTA) distribution diagrams are plotted. Thallium salts are synthesized in the regions of dominant existence of heteropoly anions H_nHoW₁₀O ₃₆ ^(9?n)? (n = 2?4). The compounds are identified using chemical analysis and IR spectroscopy.     

Comparison of chemical effects of UV radiation from spark discharge in air and a low-pressure mercury lamp

The chemical effects of UV radiation from atmospheric-pressure spark discharge and a DBK-9 low-pressure mercury lamp in distilled water and aqueous solutions of hydrogen peroxide and tryptophan have been studied. Reactive species generated in water by the both radiation sources are HO ₂ ^· radicals, acid residue ions NO ₂ ^? and NO ₃ ^? , and ammonium ions. The yield of HO ₂ ^· radicals has appeared to be the same for both sources, (1.1–1.2) × 10^?6 mol L^?1 s^?1. This is confirmed by measurements of the degradation kinetics of tryptophan, which can be destroyed by HO ₂ ^· radicals. The pH of water monotonically decreases with time during the spark discharge treatment. In the case of the mercury lamp, the pH varies insignificantly because of the competition of NH ₄ ⁺ alkali ions with the acid residues. UV radiation plays the major role in the decomposition of hydrogen peroxide.     

Boric acid

pH ranges of existence of boric acid and its ionic species H₂BO ₃ ^? , HBO ₃ ^2? , BO ₃ ^3? , and B(OH) ₄ ^? in aqueous solutions are calculated using Mathcad software package.     

Thermochemical investigation of natural antlerite

Thermal and thermochemical investigations of natural hydroxyl-bearing copper sulfate Cu₃SO₄(OH)₄??antlerite have been carried out. The stages of its thermal decomposition have been studied employing the Fourier-transform IR spectroscopy. The enthalpy of formation of antlerite from the elements ??_f H _m ^o (298.15?K)?=?(?1750?±?10)?kJ?mol^?1 has been determined by the method of oxide melt solution calorimetry. Using value of S _m ^o (298.15?K), equal to (263.46?±?0.47)?J?K^?1?mol^?1, obtained earlier by the method of adiabatic calorimetry, the Gibbs energy value of ??_f G _m ^o (298.15?K)?=?(?1467?±?10)?kJ?mol^?1 has been calculated.