Absolute determination of electrolytic conductivity for primary standard KCl solutions from 0 to 50°C

An absolute determination of aqueous electrolytic conductivity has been made for primary standards 0.01D and 0.1D (demal) potassium chloride solutions over the temperature range of 0 to 50°C in 5 degree intervals. A cell with a removable center section of accurately known length and area was used for the measurements. Values were adjusted to be in conformity with the ITS-90 temperature scale. The overall uncertainty over the entire temperature range is estimated to be 0.03%. Values at 25°C for 0.01D and 0.1D KCl solutions are 0.0014086 and 0.012852 S-cm^–1, respectively.     

Stability of nanocrystalline cellulose in aqueous KCl solutions

The electrokinetic properties and aggregation stability of nanocrystalline cellulose sols in aqueous KCl solutions have been studied at pH 5.2. Cellulose nanoparticles have been prepared via controlled degradation in a mixture of phosphotungstic and acetic acids. At electrolyte concentrations of <0.01 mol/dm³, the system is stable to aggregation. The experimentally determined threshold of fast coagulation is 0.08 mol/dm³. It has been noted that the structural component of disjoining pressure must be taken into account when considering the aggregation stability of nanocrystalline cellulose sols in terms of the DLVO theory. It has been shown that the sizes of water boundary layers decrease with an increase in the KCl concentration. The effect of medium pH on the electrokinetic potentials and sizes of aggregates has been studied.     

An update on the electrolytic conductivity values for the primary standard KCl solutions: Conversion to the ITS-90 temperature scale

A new international temperature scale has replaced the 1968 scale. Here, we report the changes required in our previous results for primary conductivity standards for 0.01, 0.1 and 1.0 Demal KCl solutions at 0,18 and 25°C.     

Electrical conductivity of aqueous polymer solutions

 Theoretical equations were proposed to adequately simulate the electrical conductivity behavior of aqueous solutions of both charged and uncharged polymers. The theory, based on the mixture equation of Boned and Peyrelasse, was experimentally verified on poly(acrylic acid) (PAA) in water and poly(ethylene oxide) (PEO) in aqueous electrolyte solutions. The data analysis suggested that both the polymer coils may be depicted as oblate ellipsoids. Subsequently, the semiaxes values of the polymer coils were determined, and they were in good agreement with the results reported in the literature. Received: 25 June 1996 Accepted: 2 October 1996     

Solubility of CO2 and H2S in alkanolamine-containing aqueous solutions

Experimental studies of the solubility of carbon dioxide and hydrogen sulfide in aqueous solutions of alkanolamines, widely used industrial absorbents of acid gases, are reviewed. A comparative analysis of methods employed by various authors is made. The available published data on the solubility of CO₂ and H₂S in solutions of primary, secondary, and tertiary alkanolamines are analyzed. Fundamental aspects of the influence exerted by various additives on the phase behavior of systems constituted by an acid gas, alkanolamine, and water are considered.     

Effect of the electrolyte concentration on cation binding in aqueous surfactant solutions.

Electrospray ionisation mass spectrometry (ESI-MS) is used for the qualitative and quantitative study of ion binding to interfaces. The ESI-MS measurements are carried out in aqueous solutions of sodium dodecyl sulphate (SDS) in the presence of NaCl, NH(4)ClO(4) , KCl, or Mg(ClO(4))(2) . The effect of the electrolyte concentration on the fractions, y(cation(+) ), of the DS(-) monomers bound to the cations is shown. Moreover, the binding stability of different cations with DS(-) monomers is determined versus the electrolyte concentration. This stability and the y(Na(+) ) values (the Na(+) ions derived from SDS), estimated in the presence of a given electrolyte, are quantitatively correlated with the electrolyte cation effect on the water structure. We also present calibration curves from which the molar concentrations of the sodium ions (derived from SDS) and of the other cations (derived from the electrolyte), bound to the SDS-micelle surface at a given electrolyte concentration, can be obtained. Besides, specific ion effects (Hofmeister effects) are considered for 1:1 electrolytes.     

Supercooling of aqueous NaCl and KCl solutions under acoustic levitation

The supercooling capability of aqueous NaCl and KCl solutions is investigated at containerless state by using acoustic levitation method. The supercooling of water is obviously enhanced by the alkali metal ions and increases linearly with the augmentation of concentrations. Furthermore, the supercooling depends on the nature of ions and is 2-3 K larger for NaCl solution than that for KCl solution in the present concentration range: Molecular dynamics simulations are performed to reveal the intrinsic correlation between supercoolability and microstructure. The translational and orientational order parameters are applied to quantitatively demonstrate the effect of ionic concentration on the hydrogen-bond network and ice melting point. The disrupted hydrogen-bond structure determines essentially the concentration dependence of supercooling. On the other hand, the introduced acoustic pressure suppresses the increase of supercooling by promoting the growth and coalescence of microbubbles, the effective nucleation catalysts, in water. However, the dissolved ions can weaken this effect, and moreover the degree varies with the ion type. This results in the different supercoolability for NaCl and KCl solutions under the acoustic levitation conditions.     

Effect of KCl on the volumetric and transport properties of aqueous tri-potassium citrate solutions at different temperatures

Density, speed of sound and viscosity measurements of binary aqueous solutions of tri-potassium citrate were performed from dilute up to near saturated concentration range at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K. Volumetric and transport properties of ternary aqueous solutions of (tri-potassium citrate + KCl) have also been measured within the molality range of KCl (0.05, 0.15, 0.25, 0.35, 0.45, and 0.55) at different temperatures. Apparent molar volume and apparent molar isentropic compressibility have been calculated from the density and speed of sound for binary and ternary aqueous solutions of tri-potassium citrate. Apparent molar volume and apparent molar isentropic compressibility of ternary aqueous solutions of (tri-potassium citrate + KCl) have been correlated with the Redlich–Mayer equation. Viscosity values of ternary aqueous solutions of (tri-potassium citrate + KCl) have been fitted with the Jones–Dole equation. The results obtained have been interpreted in elucidating the effect of tri-potassium citrate on the interaction of KCl–H₂O. Density and viscosity values of ternary aqueous solutions of (tri-potassium citrate + KCl) have been predicted successfully using the methods proposed by Laliberte (2007), Laliberte and Cooper (2004) [9], [10] and Zafarani-Moattar and Majdan-Cegincara (2009) [11].     

Electrical conductance of aqueous solutions of KCl solutions at pressures up to 2000 atm

Electrical conductance measurements are reported for aqueous KCl solutions at 25°C as a function of concentration up to 0.02 M and pressure up to 2000 atm. The data from 103 runs were analyzed with the Fuoss-Hsia-Fernandez-Prini (FHFP) equation. The standard error of fit varies from 0.018 at 1 atm to 0.12 at 2000 atm. The increase of with pressure arises from increasing nonrandomness in the distribution of errors about the FHFP equation, suggesting that modifications in the theory are necessary. Departures from the Walden product for KCl as a function of pressure are compared with MgSO₄ and CaSO₄ in aqueous solutions.     

Interactions of DL-serine and L-serine with NaCl and KCl in aqueous solutions

The activity coefficients at 25‡C of DL-serine and L-serine in aqueous solutions of NaCl and KC1 were measured. This study examines the effect of the nature of the cation of the electrolyte on the activity coefficients of the optical-isomers of serine in aqueous solutions for molality of serine up to 0.4 and molality of electrolyte up to 1. An electrochemical cell with two ion-selective electrodes, a cation, and an anion ion selective electrode,vs. a double-junction reference electrode was used to measure the activity coefficients of the electrolyte and the results were converted to the activity coefficients of serine in the aqueous electrolyte solution. The comparison of the results obtained for DL- and L-serine indicates that the two optical isomers have identical interactions with electrolytes in aqueous solutions and that for this amino acid the effect of the cation of the electrolyte is not significant. Comparison of these results with previous measurements for DL-alanine in aqueous solutions of the same electrolytes show the notable effect of the backbone of the amino acid.     

CO(2) concentration measurements on air samples by mass spectrometry

A new technique for measuring CO(2) concentration in air samples, based on mass spectrometry, is described as an alternative to the common gas chromatographic method. Using a dual inlet isotope ratio mass spectrometer (IRMS), the ratio of the abundances of the m/z peaks 44 and 28 is determined. The precision of measurements (standard deviation <3 ppmv) is generally as good as the analysis with gas chromatography for small air samples (<1 ml STP of air). A major advantage of this new method is the possibility of parallel elemental and isotopic measurements of many air components. The technique is further improved by new wide mass range mass spectrometers allowing simultaneous intensity measurements of several m/z values between 28 and 44, resulting in an uncertainty of <0.5 ppm. The precision is somewhat limited by the production of N(2)O and NO(2) from N(2) and O(2) in the ion source, which accounts for about half of the signal strength at m/z 44. Copyright 2000 John Wiley & Sons, Ltd.     

A general treatment for the conductivity of electrolytes in the whole concentration range in aqueous and nonaqueous solutions

Despite the great importance of ion transport, most of the widely accepted models and theories are valid only in the not very practical limit of low concentrations. Aiming to extend the range of applicability to moderate concentrations, a number of modified models and equations (some approximate, some fundamented on different assumptions, and some just empirical) have been reported. In this work, a general treatment for the electrical conductivity of ionic solutions has been developed, considering the electrical conductivity as a transport phenomenon governed by dissipation and feedback. A general expression for the dependence of the specific conductivity on the solution viscosity (and indirectly on concentration), from which the whole conductivity curve can be obtained, has been derived. The validity of this general approach is demonstrated with experimental results taken from the literature for aqueous and nonaqueous solutions of electrolytes.     

KCl/NaCl DMSO aqueous solutions dielectric spectra and cooperative interactions

The complex permittivity spectra of KCl/NaCl DMSO aqueous solutions were measured using microwave dielectric spectroscopy. Ion–water and dipole–water cooperative interactions are investigated by using a fractional relaxation process. Only about one cooperative relaxation was found during the cut-off relaxation time interval and the relaxation time increases with concentration increasing. Ions’ concentration dependent on effective number of water molecules in the shell around ions was calculated to reveal the interactions between K⁺, Cl^?, Na⁺ ions and DMSO molecules.     

Enthalpy of solution of CO2 in aqueous solutions of 2-amino-2-methyl-1-propanol

The enthalpies of solution of CO₂ in aqueous solution of 2-amino-2-methyl-1-propanol (AMP) 15 wt% and 30 wt% were measured at 322.5 K and pressures range from (0.2 to 5) MPa using a flow calorimetric technique. The gas solubilities were simultaneously determined from the calorimetric data. The solubilities were compared to available literature values obtained by direct measurements. The experimental enthalpies of solution were compared to the values derived from the literature vapor liquid equilibrium data. This work provides calorimetric data that will be used later for the development of a thermodynamic model to predict both solubilities and enthalpies of solution of acid gases in aqueous amine solutions.     

Association of carboxylic acids in aqueous solutions from conductivity data

Using precision conductivity data for aqueous carboxylic acid systems at 25 and 30°C, accurate thermodynamic ion association and dimerization equilibrium constants were determined. The data for formic, acetic, propionic and butyric acids are analyzed with the Fuoss-Hsia conductance equation as modified by Justice and Barthel. The treatment requires that triple ion formation is negligible.     

Comprehensive study of electrosurface properties of detonation nanodiamond particle agglomerates in aqueous KCl solutions

The electrosurface properties of nanoporous agglomerates of detonation nanodiamond (DND) particles purified from acidic impurities by dialysis are comprehensively investigated. Acid-base potentiometric titration, laser Doppler electrophoresis, and conductometry are employed to measure the adsorption isotherms $\Gamma _{H^ + } (pH)$ and $\Gamma _{OH^ - } (pH)$ of potential-determining ions, as well as the dependences of surface charge density ??₀, electrophoretic mobility u _e, and specific conductivity K _p of the agglomerates on the pH = 3.5?C10.5 of aqueous 0.0001?C0.1 M KCl solutions. The obtained adsorption isotherms indicate heterogeneity of the DND surface, i.e., the presence of different proton-donor and proton-acceptor surface functional groups. Computer simulation of the adsorption isotherms is carried out for a DND surface containing two types of functional groups, namely, acidic carboxyl (-COOH) and amphoteric hydroxyl (-COH) groups, the predominant content of which is confirmed by FTIR spectroscopy data. The optimal values are determined for the reaction constants of ionization of these groups. It is revealed that the effective conductivity of the porous agglomerates is one or two orders of magnitude higher than the conductivity of equilibrium solutions. Corresponding values of electrokinetic potential ?? are calculated as functions of pH and KCl concentration from the electrophoretic mobility of the agglomerates using different equations of electrophoresis theory. It is shown that use of the Miller formula, which takes into account the electromigration fluxes of ions and electroosmotic flows of solutions in pores of dispersed particles, yields more correct ?? potential values for DND agglomerates.     

Solvation of a hydrogen isotope in aqueous methanol, NaCl, and KCl solutions

The muon hyperfine coupling constant (hfc) of the light hydrogen isotope muonium (Mu) was measured in aqueous methanol, NaCl, and KCl solutions with varying concentrations, in deuterated water, and in deuterated methanol. The muon hfc is shown to be sensitive to the size and composition of the primary solvation shell, and the three-dimensional harmonic oscillator model of Roduner et al. (J. Chem. Phys. 1995, 102, 5989) has been modified to account for dependence of the muon hfc on the methanol or salt concentration. The muon hfc of Mu in the aqueous methanol solutions decreases with increasing methanol concentration up to a mole fraction (chiMeOH) of approximately 0.4, above which the muon hfc is approximately constant. The concentration dependence of the muon hfc is due to hydrophobic nature of Mu. It is preferentially solvated by the methyl group of methanol, and the proportion of methanol molecules in the primary solvation shell is greater than that in the bulk solution. Above chiMeOH approximately 0.4, Mu is completely surrounded by methanol. The muon hfc decreases with increasing methanol concentration because more unpaired electron spin density is transferred from Mu to methanol than to water. The unpaired electron spin density is transferred from Mu to the solvent by collisions that stretch one of the solvents bonds. The amount of spin density transferred is likely inversely related to the activation barrier for abstraction from the solvent, which accounts for the larger muon hfc in the deuterated solvents. The muon hfc of Mu in electrolyte solution decreases with increasing concentration of NaCl or KCl. We suggest that the decrease of the muon hfc is due to the amount of spin density transferred from Mu to its surroundings being dependent on the average orientation of the water molecules in the primary solvation shell, which is influenced by both Mu and the ions in solution, and spin density transfer to the ions themselves.     

Electrolytic conductivity: a reference system for aqueous solutions

To establish a system for the measurement of electrolytic conductivity in aqueous solutions with traceability to the SI, a cell has been developed with a removable central section providing an accurate determination of the geometrical constant. As the concentration unit mass/mass, based and referred to the amount of substance in the SI, is recommended by international organisations, 0.1 molal KCl samples have been prepared and analysed. Results over a temperature range from 20 degrees C to 35 degrees C are presented. The main sources of error have been estimated and relative uncertainty has been assessed to remain at the level of 0.6%. Satisfactory agreement is observed when the results are compared with the reference values available from literature.