Solubility equilibria in the system Cd(II)-2-mercaptopropionic acid at 25°C

The solubility equilibria between Cd(II) and 2-mercaptoproprionic acid in 3.0 M NaClO₄ at 25°C have been studied by e.m.f. The e.m.f. measurement with both glass and Cd(Hg) electrodes in the range 2.5 < pH < 4.8 were made in solutions where a solid phase coexists with soluble complexes Cd_qA_p. Free ligand and metal ion concentrations were calculated in order to determine the solubility product of CdA (eqn 5). From the values of the formation constants for the soluble complexes and the solubility product, the solubility constants k_spq have been computed. A general equation for the redissolution of the precipitate is proposed and a set of equilibrium constants is given.     

Activity measurements in the ternary system NaBr+NaClO4+H2O at 25°C

The activity coefficients of sodium bromide in the ternary system NaBr+NaClO₄+H₂O were determined at 25°C and constant ionic strength of 0.1, 0.5, 1, 2, and 3 mol-kg^?1 from emf of the cell without, liquid junction $$ISE - Na|NaBr(m_A ), NaClO_4 (m_B ), AgCl_{(s)} 1 Ag$$ The experimental activity coefficients were comparatively analyzed by using the Harned, Scatchard, Pitzer and Lim-HOLL treatments. All these methods are adequate for the analysis of the experimental data. The results have been compared with those of Lanier for the system: NaCl+NaClO₄+H₂O. The Gibbs excess energy of mixing was obtained and qualitatively interpreted in terms of ionic interactions.     

Enthalpies of dilution of tris-ethylenediaminocobalt(III) chloride in aqueous solution at 25°C

The enthalpies of dilution for aqueous solutions of [Co(en)₃]Cl₃, where en=1,2-diaminoethane, have been measured at 25°C, and up to m=1 mol-kg^–1, using a new large isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies L have been extracted as an empirical equation relating L and m. Comparison with other 31 and 13 aqueous systems confirms the previously suggested hydrophobic character of the [Co(en)₃]³⁺ cation.     

Volumetric study on a Co(III) rotaxane complex in aqueous solutions at 25°C

Résumé The standard partial molar volumes have been determined for [(en)₂ClCo(III)(don) Co(III)CL(en)₂] Br₄-[-CDX]-rotaxane (Rotaxane) and its component compounds, [(en)₂ClCo(III)(don)Co(III)Cl(en)₂] Br₄ (Co(III)-II), and -CDX, in aqueous solution at 25°C V^o (Rotaxane) is smaller than the sum of V^o (CO(III)-II) and V^o (-CDX) by about 28 cm³-mol^–1. Some estimations were attempted; the number of methylene groups in the cavity of -CDX, was estimated to be six and the number of water molecules expelled from -CDX cavity by hydrocarbon chain of the Rotaxane, is around four.     

Study of the behavior of chromium(III) in potassium nitrate solutions at 25°C

Solubility in the KNO₃-Cr(NO₃)₃-H₂O system at 25°C was studied by an isothermal method. The existence of solid phases of potassium nitrate and chromium(III) nitrate nonahydrate was confirmed by constructing a phase diagram, chemical analysis, and IR spectroscopy. Crystallization of potassium nitrate from aqueous solutions was studied. Potassium nitrate does not interact with chromium(III) nitrate within the range of micro and macro concentrations. The capture of chromium(III) by KNO₃ crystals is due to adsorption and occlusion of a mother solution.     

Comparative conductimetric studies of salicylic acid in methanol-water mixtures at 25 °C

The conductivity of salicylic acid in methanol-water mixtures was measured at 25 °C. Experimental data were analyzed using the Hsia-Fuoss and Fuoss-78 conductance equations and a comparison was made. The Hsia-Fuoss and Fuoss-78 methods were also used to deter-mine the thermodynamic association constants and the limiting molar conductivities for all solvent compositions. The limiting equivalent conductance decreases with an increase in the methanol content in the binary mixtures over the whole range of solvent compositions, but the variation does not give a constant value of Walden product. The electrolytes were found to be practically completely associated in all solvent mixtures studied. The association constant of salicylic acid decreases as the dielectric constants of the mixtures increase.     

The hydrolysis and fluoride complexation behavior of Fe(III) at 25°C and 0.68 molal ionic strength

Fe(III) hydrolysis and fluoride complexation behavior was examined in 0.68 molal sodium perchlorate at 25°C. Our assessment of the complexation of Fe(III) by fluoride ions produced the following results: log_F1 = 5.15₅, log_F2 = 9.10₇, log_F3 = 11.96, log_F4 = 13.7₅, where log_Fn = 5.15₅=[FeF _n ^(3-n)+ ][Fe³⁺]^–1[F^–]^–n. The stepwise fluoride complexation constants,FK _n+1, obtained in our work (where log_F K _n+1 =log_Fn) indicate that K _n+1/K _n =0.072±0.01. Formation constants for equilibria, Fe³⁺+nH₂OFe(OH) _n ^(3–n)+ +nH⁺, expressed in the form _n ^* [Fe(OH) _n ^(3-n)+ ][H⁺]ⁿ ,[Fe ³⁺]^-1, were estimated as ₁ ^* = –2.754, and ₂ ^* –7. Our study indicates that the results of previous hydrolysis investigations include very large overestimates of Fe(OH) ₂ ⁺ formation constants.     

Thermodynamics of Cm(III) in Concentrated Salt Solutions: Carbonate Complexation in NaCl Solution at 25°C

The carbonate complexation reactions of Cm(III) were studied by time-resolved laser fluorescence spectroscopy in 0–6 m NaCl at 25°C. The ionic strength dependence of the stepwise formation constants for the carbonato complexes Cm(CO₃) _n ^3–2n with n = 1, 2, 3, and 4 is described by modeling the activity coefficients of the Cm(III) species with Pitzer's ion-interaction approach. Based on the present results and literature data for Cm(III) and Am (III), the mean carbonate complexation constants at I = 0 are calculated to be: log ₁₀₁ ^o =8.1 ±0.3, log ₁₀₂ ^o =13.0 ± 0.6, log ₁₀₃ ^o =15.2 ± 0.4, and log ₁₀₄ ^o =13.0 ± 0.5. Combining these equilibrium constants at infinite dilution and the evaluated set of Pitzer parameters, a model is obtained, that reliably predicts the thermodynamics of bivalent actinide An(III) carbonate complexation in dilute to concentrated NaCl solution.     

Solubility in the ZnCl2-CO(NH2)2-HCl-H2O system at 25°C

The ZnCl₂-CO(NH₂)₂-HCl-H₂O quaternary system at 25°C was studied by the solubility method. The concentration boundaries of crystallization were established for the phases that correspond to the eutonic compositions of ternary systems, for double carbamide compounds with zinc chloride and hydrochloric acid, and for the compound ZnCl₂ · 2CO(NH₂)₂ · HCl.     

Phase formation in the ZrO(NO3)2-NaF(HF)-H3PO4-H2O system at 20°C

Phase formation in the ZrO(NO₃)₂-NaF(HF)-H₃PO₄-H₂O system was studied at 20°C and 2.0–14.5 wt % ZrO₂ in the initial solution along sections with molar ratios PO ₄ ^3? /Zr = 0.5 and 1.5 and also in the presence of hydrogen fluoride at Na/Zr = 1 and PO ₄ ^3? /Zr = 0.5, 1.0, and 1.5. Crystalline zirconium hydrophosphate Zr(HPO₄)₂ · H₂O, fluorozirconates Na₅Zr₂F₁₃ and Na₇Zr₆F₃₁ · 12H₂O, fluorophosphatozirconates NaH₂Zr₃F₃(PO₄)₄ · 3H₂O and NaZr₂F₆(PO₄) · 4H₂O, and amorphous NaZrO_0.5F(PO₄) · 4H₂O (provisional composition) were separated at room temperature. NaH₂Zr₃F₃(PO₄)₄ · 3H₂O and NaZr₂F₆(PO₄) · 4H₂O were prepared for the first time and were studied by crystal-optical, elemental, and thermal analyses, X-ray powder diffraction, IR spectroscopy, scanning electron microscopy (SEM), and X-ray microanalysis. Na₇Hf₆F₃₁ · 12H₂O was found to exist in a mixture with the hydrophosphate.     

Solubility in ternary aqueous systems including calcium chlorate and diethanolamine (triethanolamine) at 25°C

Solubility in ternary aqueous systems including calcium chlorate and diethanolamine (triethanolamine) has been studied at 25°C. Solubility diagrams have been constructed. Solubility curves consist of three branches corresponding to the crystallization of calcium chlorate, diethanolamine (triethanolamine), and compound Ca(ClO₃)₂ · NH(C₂H₄OH)₂ or Ca(ClO₃)₂ · N(C₂H₄OH)₃. The compounds have been isolated and identified by chemical analysis, X-ray powder diffraction, and thermal analysis.     

Complex formation between α-cyclodextrin and amines in water and DMF solvents

Complexation between -cyclodextrin (-CD) and aliphatic amines in water and DMF solvents was studied by calorimetry. Amines form complexes with -CD in both solvents but the nature of the complexes is quite different. In DMF the amines donate a hydrogen from the amine N–H group to the cyclodextrin forming a normal hydrogen bonded complex. In DMF solutions with large amine concentrations, complexes other than 11 are observed. In contrast, in aqueous environment the amines form inclusion complexes in which the amine alkyl group penetrates the -CD cavity and is stabilized by van der Waals interactions. The equilibrium constants for the complexes formed in water solvent increase with increasing alkyl chain length due to an entropy effect.     

Diffusion of levodopa in aqueous solutions of hydrochloric acid at 25 °C

Ternary mutual diffusion coefficients (D₁₁, D₂₂, D₁₂ and D₂₁) measured by the Taylor dispersion method are reported for aqueous solutions of {levodopa (l-dopa) + HCl} solutions at 25 °C and HCl concentrations up to 0.100 mol · dm⁻³. The coupled diffusion of l-dopa (1) and HCl (2) is significant, as indicated by large negative cross-diffusion coefficients. D₂₁, for example, reaches values that are larger than D₁₁, the main coefficient of l-dopa. Combined Fick and Nernst–Planck equations are used to analyze the proton coupled diffusion of l-dopa and HCl in terms of the binding of H⁺ ions to l-dopa and ion migration in the electric field generated by l-dopa and HCl concentration gradients.     

La(CCl3COO)3-La(ClO4)3-H2O system at 25°C

The lanthanum trichloroacetate-lanthanum perchlorate-water ternary system was studied by the isothermal solubility method at 25°C. The compositions of solid phases were studied by the Schreinemakers method. The refraction indices, specific volumes, and viscosities of liquid phases were determined. The crystallization of the initial components and, the formation of a closed area of solid solutions were established in the system.     

Mixed-Ligand Complex Formation Equilibria of Vanadium(III) with 2,2′-Bipyridine and the Amino Acids Glycine, Proline, α-Alanine and β-Alanine Studied in 3.0 mol?dm?3 KCl at 25 °C

We studied speciation of the mixed-ligand complex formation equilibria of vanadium(III) with both 2,2??-bipyridine (Bipy) and the amino acids glycine (HGly), proline (HPro), ??-alanine (H??Ala), and ??-alanine (H??Ala) by means of electromotive forces measurements emf(H) using 3.0?mol?dm^?3 KCl as the ionic medium at 25 °C. The experimental data were analyzed by means of the computational least-squares program LETAGROP, taking into account the hydrolysis of the vanadium(III) cation, the respective stability constants of the binary complexes, and the acid/base reactions of the ligands which were kept fixed during the analysis. In all four amino acid systems studied we observed the complexes [V₂O(Bipy)(B)]³⁺, [V₂O(Bipy)₂(B)₂]²⁺, [V(OH)(Bipy)(B)₂] and [V(OH)₂(Bipy)(B)], where B represents the deprotonated form of the amino acids studied in this work. The respective stability constants were determined and the species distribution diagrams as a function of pH are briefly discussed.     

Activity and Osmotic Coefficients from the Emf of Liquid Membrane Cells. IX: Mn(ClO4)2 and MnSO4 in Water at 25°C

The relative activity coefficients of MnSO₄ and Mn(ClO₄)₂ were measured downto about 5×10^–5 mol-kg^–1 by means of cells with ion-exchange liquid membranes.The measurements at high dilution provide an answer to the age-old problem ofabsolute values of the activity coefficients for MnSO₄. They also lead to acorrection of the activity coefficients for Mn(ClO₄)₂, whose literature values arefound to be biased by ca. 6.5%. Like other bivalent metal sulfates, MnSO₄does not obey the Debye—Hückel law inasmuch as negative instead of positivedeviations from the limiting law are observed in the dilute regions. The possibilityfor this kind of behavior to denote ion association is discussed. The best-fitparameters of Pitzer's equation, able to provide accurate values of the activityand osmotic coefficients of the two salts for any concentration, are reported.     

Viscosity of Potassium Trioxalato Complexes of Al(III), Fe(III), Co(III), and Cr(III) in Aqueous Solution Between 15° and 35°C

The viscosity of dilute aqueous solutions of K₃[AI(ox)₃]·3H₂O, K₃[Fe(ox)₃]·3H₂O, K₃[Co(ox)₃]·3H₂O, and K₃[Cr(ox)₃]·3H₂O complexes, as well as K₂(ox)·H₂O, were measured between 15 and 35°C. Those of CoCl₂, 6H₂O, FeCl₃, A1₂(SO₄)₃·18H₂O, and CrCl₃·6H₂O were measured at 25°C. These data were analyzed by the Jones–Dole equation. The ionic B coefficients of the above complex anions were discussed in terms of ion–solvent interactions and the overall change in B associated with complex formation.     

Osmotic and Activity Coefficients of CH3SO4Na(aq) and CH3SO4K(aq) at 25°C

The osmotic and activity coefficients of aqueous sodium and potassium methyl sulfates have been determined at 25°C by the isopiestic method, in the molality range from ca.0.2 to 25 and 19 mol-kg^–1, respectively. The results have been discussed in terms of the ion–ion and ion–water interactions on the basis of the Pitzer and Mayorga model and a method developed in our laboratory.