V. V. Shcherbakov

Electrical conductivity of the ammonia-water system

The electrical conductivity (EC) of the ammonia-water system was studied in the concentration range 0.1–10 mol/L ammonia and the temperature range 15–60°C. The maximal EC of aqueous ammonia at a given temperature is proposed as the parameter for generalizing experimental results. The normalized EC was calculated as the ratio of the EC of aqueous ammonia of a given concentration to the maximal EC at a given temperature. Over the ranges of the concentrations and temperatures studied, all normalized ECs fall on one curve. The EC activation energy was analyzed as a function of ammonia concentration and temperature.

Electric Conductivity of Concentrated Aqueous Solutions of Propionic Acid, Sodium Propionate and Their Mixtures

Specific electric conductivity (EC) of concentrated aqueous solutions of propionic acid (PA), sodium propionate (SP), and water/PA/SP mixtures is measured in the temperature range of 15–90°C. Specific EC passes a maximum at the increase in the electrolyte concentration in the mixtures of water/PA, water/SP, and water/PA/SP containing a similar PA concentration. The maximum EC value of the aqueous PA solution at the given temperature is used as the generalizing term. It is shown that the values of reduced EC (ratio of EC and its maximum value at the given temperature) fall on a single curve in the whole studied range of temperatures and concentrations of the water/PA mixture. The EC activation energy is calculated for all the studied solutions. It is found that the EC activation energy of these solutions decreases at the temperature increase and grows at the increase of the concentration of electrolyte.

Dielectric properties of solvents and their limiting high-frequency conductivity

The behavior of the limiting high-frequency (HF) conductivity of water, methanol, ethanol, and propanol in a wide temperature range is considered. As the temperature is increased to its critical value, the static permittivity and the dipole relaxation time of the polar solvents decrease monotonically; however, the limiting HF conductivity, which is determined by their ratio, passes through a maximum. The maximum is explained by differences in the behavior of the temperature dependences of the relative temperature coefficients (RTCs) of static permittivity and the dipole relaxation time. It is shown that the maximum on the temperature dependence of the limiting HF conductivity corresponds to the equality of the RTCs of static permittivity and the dipole relaxation time. It is noted that in the temperature range corresponding to the maximum limiting HF conductivities of water and alcohols, the temperature dependences of the ion product of water and the conductivity of the considered polar solvents and solutions of inorganic salts in them also pass through maxima.

High-frequency conductivity of mixtures of water with methanol, ethanol, and propanol

High-frequency (HF) electric conductivity (EC) of mixtures of water with methanol, ethanol, and propanol was analyzed. The limiting HF conductivity decreased at increasing alcohol content in the mixture and passed through a maximum at 2455 MHz. The rate of HF heating of the aqueous solutions of alcohols was determined using a Discover Bench Mate microwave system at a frequency of 2455 MHz. The maximum rate of HF heating was observed in solutions with the highest HF conductivity.

Dielectric properties and high-frequency conductivity of the sodium chloride-water system

An analysis has been performed of the dielectric characteristics and high-frequency (hf) electrical conductivity (EC) of aqueous solutions of NaCl. A method of the estimation of the static dielectric constant and of the time of dipole relaxation of concentrated aqueous solutions of NaCl in a wide range of concentrations and temperatures has been suggested. It has been shown that the limiting hf EC of the solutions and the hf EC at the frequency of 2455 MHz decrease with increasing salt concentration and differently change with increasing temperature: the limiting hf EC increases, whereas the hf EC at the frequency of 2455 MHz decreases. The decrease in the hf EC leads to a reduction of the rate of the hf heating of the NaCl solution with increasing salt concentration.

High-frequency electric conductivity of mixtures of water with acetone, dimethyl sulfoxide, and carbamide

The high-frequency (HF) electric conductivity (EC) of water-acetone, water-dimethyl sulfoxide (DMSO), and water-carbamide mixtures was analyzed. The limiting high-frequency conductivity decreased as the content of the organic component in the mixture increased. When the acetone and DMSO concentrations increased, the high-frequency conductivity passed through a maximum at 2450 MHz and increased with the carbamide concentration in its mixtures with water. The optimum conditions for the absorption of HF energy by the aqueous organic mixtures under study were determined.

Ultimate high-frequency conductivity of solvent and electroconductivity of electrolyte solutions

The temperature curves of the ultimate high-frequency electroconductivity of water and acetonitrile were analyzed. The temperature curves of specific electroconductivity of aqueous 0.1 M sodium chloride solution and acetonitrile 0.1 M 1-butyl-3-methylimidazol trifluoromethane sulfonate were compared. The electroconductivity activation energy of solutions was found coinciding with the ultimate high-frequency electroconductivity activation energy of solvents within the experimental error. The specific electroconductivity of solutions was shown to increase at higher temperature in direct proportion to the ultimate high-frequency electroconductivity of solvents.

Dielectric Characteristics of Water and Electric Conductivity of Aqueous Electrolytes

The specific electric conductivities (ECs) of concentrated aqueous solutions of electrolytes were shown to be comparable to the limiting high-frequency (HF) EC of water. The limiting HF EC of water is determined by the ratio of the absolute dielectric constant to the dipole dielectric relaxation time. It was assumed that the specific EC of an aqueous solution cannot exceed the limiting HF EC of water. The specific ECs of the 1.0 М aqueous solutions of lithium, sodium, and potassium chlorides were calculated from the limiting HF EC of water. At elevated temperatures, the specific ECs of aqueous salts were shown to increase in direct proportion to the limiting HF EC of water.

Electrical conductivity in alkali metal hydroxide-water systems

The specific electrical conductivity (EC) of the KOH-H2O system was analyzed in the range 0–100°C. The maximal EC of KOH solutions for a given temperature and the concentration corresponding to the maximal specific EC were used as generalizing parameters. The values of normalized EC (the ratio of the EC to its maximal value for a given temperature) fall on one curve for temperatures over a range of 0–100°C and concentrations over a range of 0.01–12 mol/L if the normalized concentration (the ratio of the solution concentration to the concentration corresponding to the maximal specific EC) is used as the argument. The normalized EC values for NaOH-H2O and LiOH-H2O systems fall on the same curve. Analytical expressions fitting normalized EC as a function of concentration are given.

Electrical conductivity of associated electrolyte-water systems

The specific electrical conductivity (EC) of concentrated aqueous solutions of tartaric and oxalic acids was measured in the range 15–90°C. Specific electrical conductivity versus concentration and temperature relationships were analyzed for the acids studied in this work and for formic, acetic, propanoic, butanoic, chloroacetic, dichloroacetic, and trichloroacetic acids, as well as for aqueous ammonia. As the electrolyte concentration increases, the EC passes through a maximum whose position is independent of temperature. The maximal EC value of an aqueous solution of an associated electrolyte for a given temperature and the concentration corresponding to this maximal EC were used as generalizing parameters. Over the entire ranges of the temperatures and concentrations studied, normalized EC values (normalized EC is the ratio of the current EC to its maximal value for a given temperature) for all electrolytes considered fall on one curve provided that the argument is a normalized concentration (which is the ratio of the current solution concentration to its value at which specific EC has a maximal value).