Densities and apparent molal volumes of aqueous CaCl2 and MgCl2 solutions

The Pitzer ion interaction model has been used to evaluate literature data for the densities of aqueous CaCl₂ and MgCl₂ solutions between 0 and 100°C. The selected data can be adequately fitted by setting ^(1),v equal to zero. The variations of ^(0),v and C ^v with temperature have been found to be linearly correlated. The uncertainty in the calculated density is lower than 50 ppm below 1M but raises to 300 ppm at high concentrations. When plotted vs. the square root of the molality, the apparent molal volume of MgCl₂ shows a change at a concentration where a transition in the speed of sound has already been reported by Millero, et al.     

Protonation and complex formation of 5-sulfosalicylate in NaCl,CaCl2 and MgCl2 aqueous media. Speciation in synthetic seawater

The binding capacity of 5-sulfosalicylic acid (ssa) towards cationic macro-components of natural waters has been investigated in different ionic media (NaCl, MgCl2 and CaCl2 aqueous solutions) and in the ionic strength range 0 < or = I < or = 1 mol dm-3. In order to contribute to the speciation of this multi-sites ligand, measurements have been carried out also in a synthetic seawater (SSWE) containing the major components of seawater (Na+, K+, Ca2+, Mg2+, Cl- and SO4(2-)). Measurements have been performed by potentiometry ([H+]-glass electrode), at t = 25 degrees C. A critical analysis on the experimental and literature data is also given.     

Radioluminescence of ice containing MgCl2 and CaCl2

The efficiency of electron trapping and reactions in ice containing MgCl₂ or CaCl₂ (0.5–5 mol dm^-3) and γ-irradiated at 77 K was investigated by isothermal—(ITL) and radiothermo— (RTL)—luminescence.Both ITL and RTL emissions are influenced by solute concentration in a similar way, revealing a maximum at ca 3.5 mol dm^-3 MgCl₂ and at ca 2.5 mol dm^-3 CaCl₂.The RTL emission exhibits two broad peaks. The low temperature peak RTL_I is only slightly dependent on matrix composition, whereas the position of the high temperature peak RTL_II shifts with glass transition point of the matrix.The influence of scavengers NaNO₃ and CH₃OH on radioluminescence (RL) was also investigated and found to be dependent on the nature of the cation.It is suggested that the RL emission is due to radiative recombination of e^-_t (e^-_ir, e^-_vis) with H atoms, metal cations and Cl^-₂ ion radicals.     

Determination of metal impurities in ultrapure CaCl2 and MgCl2 by ICP OES

An effective, rapid and simple analytical method for the determination of Na, K, Ca, Mg, Cd, Pb, Ba, Fe, Mn, Sr, Zr, Cu, Zn and Al at mg kg⁻¹ levels in the ultrapure salts MgCl₂ and CaCl₂ using optical emission spectrometry was developed. Optimisation of the operation conditions was performed with real samples of ultrapure MgCl₂ and CaCl₂. The results of the determination with multi-elemental water standards were compared to the internal standardisation, the standard addition method, and the maximum allowable content of the above mentioned elements in pure chemicals. The method was shown to be very sensitive with the following limits of detection: Na 1.01, K 3.12, Ca 0.263, Mg 0.275, Cd 0.0832, Pb 0.482, Ba 0.0153, Fe 0.0528, Mn 0.0473, Sr 0.0203, Zr 0.638, Cu 0.0732, Zn 0.0686 and Al 0.459 (all in mg kg⁻¹). The method exhibited satisfactory precision, high analytical recoveries, linear responses of an accuracy of at least 4 orders of magnitude and low contamination susceptibility.     

Activity coefficients of aqueous perchloric acid

Mean ionic activity coefficients for aqueous perchloric acid at 25°C were obtained from the emf of a HClO₄ concentration cell (m=1×10^–3–1.5) containing a ClO ₄ ^– ion solution electrode and a glass electrode. The results of an application of the Pitzer equations are compared with those previously reported from several different measuring methods. Perchloric acid activity coefficients have been calculated for the mixture HClO₄–NaClO₄. In both cases, good agreement has been obtained between our results and those derived from the isopiestic method.Deceased November 15, 1984.     

Activity coefficients in binary electrolyte mixtures HCl + MgCl2 + H2O at 298.15°K

Activity coefficients of hydrochloric acid in aqueous mixed solutions with magnesium chloride have been determined at 298.15°K from electromotiveforce measurements of the cell Pt, H₂(g, 1 atm.)HCl(m_A), MgCl₂(m_B)AgClAg at constant total ionic strengths of 0.1, 0.5, 1.0, 2.0, and 3.0 moles-kg^–1. The data were interpreted in terms of Scatchard's and Pitzer's equations whereupon it was found that the former gave a better fit of the experimental data but the latter were reasonably adequate. Activity coefficients for magnesium chloride in the mixtures were derived using Pitzer's equations.     

拉曼光谱研究CaCl2和MgCl2对水结构的影响

测试了CaCl2、MgCl2溶液(浓度小于1.0 mol•L-1)的OH伸缩振动区域的拉曼光谱.对所得到的拉曼光谱进行了计算机去卷积处理,并由此计算了不同溶液中水的四面体结构的百分数.研究表明,CaCl2、MgCl2对水中四面体结构有破坏作用，且CaCl2的破坏作用比MgCl2大.与17O核磁共振结果对比与分析,认为CaCl2、MgCl2虽然破坏水中的四面体结构,但通过促进含氢键数少的水分子形成氢键,故从总体上促进水的缔合结构.     

高温及超临界条件下 MgCl2与CaCl2水溶液中离子水化与缔合的量子化学计算

对NaCl等碱金属水溶液的研究表明,室温条件下,离子在溶液中以水合形式存在,而在高温及超临界时,阴阳离子将结合成为离子对．采用量子化学计算,研究了MgCl2与CaCl2水溶液中水化与缔合的情况．通过Gaussian98软件包计算了阳离子的水化自由能以及离子对的生成能,从而获得水合离子与离子对的热力学稳定性及其随温度、压力的变化情况．通过比较热力学稳定性,考察了两种溶液中水化与缔合的变化情况．研究结果表明,MgCl2与CaCl2水溶液中离子水化与缔合的变化趋势与碱金属溶液基本一致,但是存在一个过渡区域,该区域内离子对与水合离子共存,因此需要采用不同于碱金属溶液的方法处理MgCl2与CaCl2水溶液．     

Concentration dependent spectral changes of electrons trapped in MgCl2 and CaCl2 glasses. A pulse radiolysis study

The aqueous MgCl₂ and CaCl₂ glasses were subjected to pulse radiolysis at 87 K. The time evolution and concentration dependence of e^-_t optical absorption spectra was examined.For MgCl₂ glasses the increase of Mg²⁺ concentration from 2.6 to 5 mol dm^-3 is followed by the shift of λ_max from 665 to 615 nm. For CaCl₂ glasses the concentration change from 3.1 to 4.5 mol dm^-3 Ca²⁺ causes the shift of λ_max from 625 to 590 nm. The blue shift is also observed during partial decay of e^-_t on μs time scale.With increasing concentration of electrolyte the contribution of e^-_ir to the total e^-_t absorption decreases, whereas that of e^-_vis increases.The ratio of [e^-_ir]/[e^-_vis] measured on micro-second time scale is significantly higher for Mg²⁺ than Ca²⁺ glasses.     

Activity coefficients of NaBF4 in aqueous solution

The activity coefficients of NaBF₄ in water were experimentally determined at 288.15, 298.15, and 308.15 K from emf measurements of the following electrochemical cell without transference containing two ion selective electrodes (ISE):

Na-ISE|NaBF₄(m)|BF₄-ISE     

Mutual diffusion coefficients of aqueous MnCl2 and CdCl2, and osmotic coefficients of aqueous CdCl2 at 25°C

Volume-fixed mutual diffusion coefficients have been measured for aqueous MnCl₂ and CdCl₂ solutions from 0.004 to 4.93–5.00 mol-dm^–3 (M) at 25°C. Diffusion coefficients for MnCl₂ decrease to a minimum, rise to a maximum, and then decrease rapidly; such behavior is typical for strong electrolytes. In contrast CdCl₂ diffusion coefficients decrease continuously with concentration; similar behavior is known for certain other associated electrolytes. Since thermodynamic diffusion coefficients for both salts are qualitatively similar, diffusion differences may be primarily due to thermodynamic rather than mobility factors. Isopiestic data were measured for CdCl₂ from 1.79 to 7.29 mol- (kg H₂O)^–1, and critically compared to other isopiestic and emf data for CdCl₂. Higher quality emf data are completely consistent with isopiestic data. Recommended smoothed values of activity coefficients, osmotic coefficients, water activities, and activity derivatives are given for CdCl₂ at 25°C.Work performed under the auspices of the Office of Basic Energy Sciences (Geosciences) of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.     

Activity coefficients and diffusion coefficients of dilute aqueous solutions of lithium,sodium, and potassium hydroxides

A simplified version of Harned's conductimetric technique has been used to measure binary diffusion coefficients of aqueous lithium, sodium, and potassium hydroxides at 25°C from 0.002 to 0.14 mol-dm^–3. Because of the large difference in mobility between OH^– and the cations, the electrophoretic effect tends to reduce the rate of diffusion of the alkali metal hydroxides; the largest effect is observed for LiOH solutions. The measured diffusion coefficients are in excellent agreement with predictions of the Onsager-Fuoss theory of ion transport. Precise activity coefficients determined from the diffusion measurements are compared with activity coefficients obtained previously by emf methods.     

Thermodynamics of Electrolytes. 13. Ionic Strength Dependence of Higher-Order Terms; Equations for CaCl2 and MgCl2

While the original ion-interaction (Pitzer) equations of 1973 were adequate for many electrolytes to the limit of solubility, additional terms are needed for some systems of large solubility. A simple pattern of ionic-strength dependence is proposed for third, fourth, and higher virial coefficients. It is found to be very effective in representing the complex behavior of CaCl₂(aq) as well as that of MgCl₂(aq) at 25°C. Equations without ion association are presented for each system that are valid for the full range to 11.0 and 5.9 mol-kg^–1, respectively, as well as simpler equations for limited molality ranges.     

A study of the vibrational motions of water in an aqueous CaCl2 solution

A detailed analysis of the vibrational motions of water in a 1.1 M aqueous CaCl₂ solution is presented on the basis of molecular dynamics computer simulations. Autocorrelation functions corresponding to approximate normal coordinates are constructed and evaluated separately for the hydration water of the ions and for the bulk water of the solution. Approximate lifetimes for the intramolecular motions are estimated. The theoretical results are compared with experimental ones from IR spectroscopy of water-base complexes.     

Viscosity of aqueous NH4Cl and tracer diffusion coefficients of ions,water and non-electrolytes in aqueous NH4Cl,KI, and MgCl2 at 25°C

Viscosities for aqueous NH₄Cl and tracer diffusion coefficients for²²Na⁺,³⁶Cl^–, HTO, and CH₃OH, acetone and dimethylformamide (all¹⁴C-labelled) in NH₄Cl supporting electrolyte are reported for 25°, together with tracer diffusion coefficients for²²Na⁺,³⁶Cl^–, and¹⁴CH₃OH in 1M KI, and for¹⁴CH₃OH in 1M MgCl₂. The diffusion coefficient of HTO in NH₄Cl solutions is slightly larger, for most of the concentration range investigated (0.05 to 4.5 M), than the value for pure water and is almost unaffected by the supporting electrolyte up to about 4M. Similar behavior is shown by CH₃OH, acetone and dimethylformamide in NH₄Cl solutions. Onsager limiting law behavior is approached by Cl^– at NH₄Cl concentrations in the 0.05–0.1M region but at much lower concentrations by Na⁺.     

Diastereoselective hydrogenation of α,β-dehydrodipeptides bearing unsaturatedN-terminal amino acids and of ther complexes with CaCl2 and MgCl2

The formation of complexes of dehydrodipeptides bearingN-terminalN-benzoyl-O-methyl-α,β-dehydrotyrosine orN-benzoyl-α,β-dehydrovaline residues with Ca²⁺ and Mg²⁺ ions enhances the diastereoselectivity of their hydrogenation;de of 66% and 80% were achieved. This method of increasing the stereoselectivity of hydrogenation is applicable to various dehydroamino acids at both theC- andN-termini of dehydrodipeptides. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 345–347, February, 1997.     

Activity coefficients of alkyl sulfate and alkylsulfonate ions in aqueous and water-salt premicellar solutions

Potentiometry has been employed to determine the activity coefficients of n-decyl sulfate and n-alkyl(C₅–C₁₀)sulfonate ions in aqueous solutions of their sodium salts containing NaCl or Na₂SO₄ as a background electrolyte. The selectivity factors have been estimated for ion-selective electrodes exhibiting responses to surfactant ions in the presence of inorganic salts. The pattern of the dependences of the activity coefficients of the surfactant anions on the length of their hydrocarbon radicals and the nature of functional groups has been revealed. The results obtained have been compared with the data on long-chain carboxylates.     

Physicochemical study of ovalbumin in the presence of sodium dodecyl sulphate in aqueous media

The interactions of sodium dodecyl sulphate with ovalbumin in aqueous solution at room temperature are described for a wide concentration range of both substances. A phase diagram covering a wide range of concentrations shows a total of five different morphologies. Dynamic light scattering of the samples from each morphology offered better understanding of the different structures (between three and four) present in the solution. The amount of ovalbumin present in the solution was confirmed with differential scanning spectroscopy, while the interactions between sodium dodecyl sulphate and ovalbumin were interpreted by zeta potential and electrical conductivity measurements.