Conductimetric Studies Research Articles

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

Conductivity data of salicylic acid in methanol–water mixtures were measured at 25°C. The data were analyzed in two methods, the Hsia–Fuoss’s and Fuoss 78’s conductance equations and a comparison was made. The two methods concern the derivation of thermodynamic association constants and limiting molar conductivities for all solvent compositions. The limiting equivalent conductance decreases with the increase of methanol content in the binary mixtures over the whole range of the solvent composition, but the variation does not give a constant value of Walden product. The electrolytes were found to be practically completely associated in all studied solvent mixtures. The association constant of acid decreases with the increase in relative permittivity of the mixtures. The values of ionic coefficients of self diffusion and the ionic conductance at infinite solutions were estimated.

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.

Spectroscopic, Thermal, Magnetic and conductimetric studies on some 7-hydroxy-4-methyl-8-(arylazo)coumarins and their complexes with some divalent transition metal ions

Spectroscopic, Thermal, Magnetic and conductimetric studies on some 7-hydroxy-4-methyl-8-(arylazo)coumarins and their complexes with some divalent transition metal ions

Ligational behavior of Schiff bases towards transition metal ion and metalation effect on their antibacterial activity

New Schiff bases pyrazine-2-carboxylicacid (phenyl-pyridin-2-yl-methylene)-hydrazide (Hpch-bp) HL1 and pyrazine-2-carboxylicacid (pyridin-2-ylmethylene)-hydrazide (Hpch-pc) HL2 derived from condensation of pyrazine carboxylic hydrazide (Hpch) with 2-benzoyl pyridine (bp) or pyridine 2-carbaldehyde (pc) and their transition metal complexes of type ML(1–2)2 have been synthesized, where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). Characterization of ligands and their metal complexes was carried out by elemental analysis, conductimetric studies, magnetic susceptibility, spectroscopic techniques (IR, UV–VIS, NMR, ESR, Mass) and thermogravimetric analysis. The physico-chemical studies revealed octahedral geometry or distorted octahedral geometry around metal ion. These azomethine Schiff base ligands acted as tridentate ▪ coordinating through carbonyl, azomethine and pyridine nitrogen present in the ligand. The thermodynamic and thermal properties of the complexes have been investigated and it was observed on the basis of these studies that thermal stability of complexes follows the order Mn<Zn<Cu<Co<Ni. The ligands and their complexes were tested for in vitro antibacterial activity at different concentrations against bacteria viz. Gram positive Bacillus subtilis, Micrococcus luteus and Gram negative Pseudomonas aeruginosa, Pseudomonas mendocina. A marked enhancement in biocidal activity of the ligands under similar experimental conditions was observed as a consequence of coordination with metal ions. The trend of growth inhibition in the complexes was found to be in the order: Cu>Mn>Ni>Co>Zn.

Potentiometric and conductimetric studies of chemical equilibria for pyridoxine hydrochloride in aqueous solutions: simple experimental determination of pKa values and analytical applications to pharmaceutical analysis

The combination of two low-cost classical procedures based on titrimetric techniques is presented for the determination of pyridoxine hydrochloride in pharmaceuticals samples. Initially some experiments were carried out aiming to determine both pKa1 and pKa2 values, being those compared to values of literature and theoretical procedures. Commercial samples containing pyridoxine hydrochloride were electrochemically analysed by exploiting their acid-base and precipitation reactions. Potentiometric titrations accomplished the reaction between the ionizable hydrogens present in pyridoxine hydrochloride, being NaOH used as titrant; while the conductimetric method was based on the chemical precipitation between the chloride of pyridoxine hydrochloride molecule and Ag+ ions from de silver nitrate, changing the conductivity of the solution. Both methods were applied to the same commercial samples leading to concordant results when compared by statistical tests (95 and 98% confidence levels). Recoveries ranging from 99.0 to 108.1% were observed, showing no significant interference on the results.

Potentiometric and conductimetric studies of chemical equilibria for pyridoxine hydrochloride in aqueous solutions: simple experimental determination of pKa values and analytical applications to pharmaceutical analysis

The combination of two low-cost classical procedures based on titrimetric techniques is presented for the determination of pyridoxine hydrochloride in pharmaceuticals samples. Initially some experiments were carried out aiming to determine both pKa1 and pKa2 values, being those compared to values of literature and theoretical procedures. Commercial samples containing pyridoxine hydrochloride were electrochemically analysed by exploiting their acid-base and precipitation reactions. Potentiometric titrations accomplished the reaction between the ionizable hydrogens present in pyridoxine hydrochloride, being NaOH used as titrant; while the conductimetric method was based on the chemical precipitation between the chloride of pyridoxine hydrochloride molecule and Ag+ ions from de silver nitrate, changing the conductivity of the solution. Both methods were applied to the same commercial samples leading to concordant results when compared by statistical tests (95 and 98% confidence levels). Recoveries ranging from 99.0 to 108.1% were observed, showing no significant interference on the results.

Vibrational spectroscopic and conductimetric studies of lithium battery electrolyte solutions

Extremely high concentrated solutions of lithium perchlorate in formamide and acetonitrile equimolar mixture were investigated by spectroscopic and conductimetric techniques. The spectral changes observed in the characteristic bands of the solvents, the appearance of the band at 939 cm −1 and the slight increase of conductivity in all solutions were interpreted in terms of a solvent separated ion pairs model. In fact, the mixture of solvents with considerable differences in the donor–acceptor characters allows to prepare electrolytic solutions where the contact ion pairs formation seems uncertain.

CTAB aggregation in aqueous solutions of ammonium based ionic liquids; conductimetric studies

The electrical conductivity/concentration data of aqueous solutions of n-hexadecyl-trimethylammonium bromide (CTAB), an cationic surfactant, with two ammonium based ionic liquids propyl-(2-hydroxyethyl)-dimethyl-ammonium bromide, (C3Br), butyl-(2-hydroxyethyl)-dimethyl-ammonium bromide, (C4Br) of high melting points (>373 K) were determined in the temperature range 298.15–328.15 K. These data were used to determining the critical micelle concentration (CMC) in function of concentration and temperature. The two ionic liquids and the surfactant have the same anion and the ammonium based cation. The influence of ionic liquids on the micellisation process of the CTAB is discussed.

Conductimetric studies of chitosan in aqueous medium

Conductimetric studies of two aqueous chitosan salts systems are presented. These salts were prepared dissolving the polyelectrolyte with desionised water and using an excess of the corresponding stoichiometric amount of acid (HCl or HNO3) and then purified by dialysis. Limit equivalent conductance (Λo) was obtained by fitting the experimental conductimetric results to a fifth order polynomial function. This result was employed to determine classical conductimetric parameters in dilution limiting conditions, i.e., charge parameter (ξ), polyelectrolyte equivalent ionic conductivity (λpo), fractional hydrodynamic coefficient (f), etc., employing Kohlrausch law for independent ions migration. We have found a remarkable agreement between experimental and theoretical results when Rinaudo equation was employed to calculate ξ. Additionally, our conductimetric studies show that equilibrium constants are similar for both systems when K values are obtained from plots of Λ2/[Λo(Λo-Λ)] vs. 1/cp.

Behaviour of a binary solvent mixture constituted by an amphiphilic ionic liquid, 1-decyl-3-methylimidazolium bromide and waterPotentiometric and conductimetric studies

We investigated the properties of 1-decyl-3-methylimidazolium bromide (DMImBr), a molten salt at room temperature, and its mixtures with water in the whole proportions. At low concentrations, this salt behaved like a classical cationic amphiphile. Its critical micellar concentration (cmc) was determined by conductimetry and by measuring electromotive forces (EMF) with bromide or cationic surfactant-selective electrodes. Moreover, the association rate of the counter ion to micelle has been determined on a wide range of concentrations, allowing characterising the micellisation equilibrium by a solubility product. The conductivity of this liquid electrolyte in mixtures with water was maximal at high concentrations. We modelled this behaviour, taking into account the molar volume fraction of both phases. Our results show that these solutions, which are composed of dispersed aggregates, behave like mixtures of two phases that interpenetrate themselves.

Superionic Transport in Fluoride Composites and Glasses

Data on previous conductimetric studies of ionic transport in fluoride composites and vitreous materials are compiled. The F- conductivity of composites 21SrF2 · 79LaF3 (content, mol %) and 34NaF · 66PbF2 reaches 0.007 S cm-1 at 500 K and that of glasses based on InF3 and PbF2, 6 × 10-5 S cm-1 at 400 K, which exceeds that of β-PbF2 and LaF3 crystals.

Behaviour of a binary solvent mixture constituted by an amphiphilic ionic liquid, 1-decyl-3-methylimidazolium bromide and water: Potentiometric and conductimetric studies

We investigated the properties of 1-decyl-3-methylimidazolium bromide (DMImBr), a molten salt at room temperature, and its mixtures with water in the whole proportions.At low concentrations, this salt behaved like a classical cationic amphiphile. Its critical micellar concentration (cmc) was determined by conductimetry and by measuring electromotive forces (EMF) with bromide or cationic surfactant-selective electrodes. Moreover, the association rate of the counter ion to micelle has been determined on a wide range of concentrations, allowing characterising the micellisation equilibrium by a solubility product.The conductivity of this liquid electrolyte in mixtures with water was maximal at high concentrations. We modelled this behaviour, taking into account the molar volume fraction of both phases.Our results show that these solutions, which are composed of dispersed aggregates, behave like mixtures of two phases that interpenetrate themselves.

Potentiometric, spectrometric, thermal and conductimetric studies on some 3-phenyl-4-(arylazo)-5-pyrazolones and their complexes with divalent cobalt metal ion

3-phenyl-4-arylazo-5-pyrazolones (I–IV) have been synthesized and characterized by elemental, infrared (IR), ultraviolet and visible spectra (UV–Vis), proton nuclear magnetic resonance ( 1H NMR) and Mass spectra. It has been proved that these compounds exhibit a keto-enol tautomerism in solution. The donor character of the substituent increases the enol form. The ionization constants of the investigated ligands have been determined potentiometrically and found to decrease in the order OCH 3(IV)>CH 3(III)>H(I)>Cl(II). The Co(II) complexes of the investigated 3-phenyl-4-arylazo-5-pyrazolones (I–IV) have been prepared and characterized by elemental and thermal analyses as well as by IR, UV–Vis, electronic transition, potentiometric, conductimetric and magnetic measurements. The data suggest octahedral geometry for Co(II) (1:1) complexes and tetrahedral for Co(II) (2:3) complexes.

Conductimetric Studies of Charge Transfer Complexes of p‐Chloranil with Some Alicyclic Amines in Polar Media

AbstractThe stoichiometry of charge‐transfer complexes which ionise in polar media has been studied by conductimetric titration technique in the systems morpholine‐p‐chloranil (CA), piperidine‐CA and pyrrolidine‐CA in three different polar solvents namely N,N‐dimethylformamide, acetonitrile and dimethylsulfoxide at different temperatures of 10, 15, 18, 20, 25 and 30 °C. The stoichiometric ratios of these complexes were found to vary from 1:1 to 1:4 (acceptor: donor) depending on the system, temperature and solvent used. The ασM‐values of these complexes have been reported. The effect of solvents, temperatures and types of electron donors on the σP‐values has been examined.

Preparation, Characterization and Thermal Study of New Cerium(IV) Complexes with the Salicylidene-2-Aminothiophenol Schiff Base

New complexes of the titled Schiff base with cerium(IV) ion have been synthesized and characterized by elemental analyses, conductimetric, IR and 1H NMR studies and thermogravimetric analysis. The results suggest that the Schiff base acts as a bivalent anion with tridentate ONS donors derived from the phenolic oxygen, azomethine nitrogen and thiophenolic sulfur. The complexes formed are non-electrolytes with the general formulae [ML(NO3)2H2O] and [M(HL)2(NO3)2]. The thermal decomposition of the complexes follows first order kinetics and the thermodynamic parameters of the decomposition are reported.

Synthesis and characterization of new diisocyanide rhenium complexes. Comparison with the homoleptic 99mTc complex

The new diisocyanide ligand L possessing a polyether backbone was synthesized and its complexing ability towards metal such as 99mTc, Cu and Re was evaluated. Using the γ-emitting 99mTc isotope (at the non-carrier added level), L led to the formation of a cationic species whose biodistribution in Swiss mice revealed a moderate but lasting heart uptake. No redox properties of the ligand were observed by complexation since reaction with a Cu II salt led to the formation of a Cu II complex, characterized by EPR, IR and elemental analysis. Rhenium complexation gave two new chelates [Re IIICl 3PPh 3L] and [Re I 3]BPh 4, identified by IR NMR, elemental analysis and conductimetric studies. The usefulness of rhenium chemistry to approach 99mTc properties is discussed.

Phase diagrams of pectin-calcium systems: Influence of pH, ionic strength, and temperature on the gelation of pectins with different degrees of methylation

The effects of ionic strength, pH, and temperature on the gelation of pectin-calcium systems were studied on an apple pectin; the influence of the degree of methylation (dm) was investigated on a family of well-characterised citrus pectins obtained by acid-catalyzed deesterification. The reaction led to a decrease in intrinsic viscosities by hydrolysis of glycosidic bonds and in neutral sugar content by elimination of the neutral fraction. Ion-exchange chromatography indicated that the deesterification did not change the charge distribution along the pectic backbone, which was confirmed by potentiometric and conductimetric studies. These methods showed that the charge distribution was statistical in apple and citrus pectins and that no egg-box can occur. Phase diagrams (sol-gel-syneresis), established as calcium concentration versus reduced polymer concentration, showed that gelation was possible before the overlapping of chains because of the strong interactions of calcium with pectins. An increase in the ionic strength, a neutral pH, and a decrease in the setting temperature and in the dm lower the amount of calcium required to give a gel, which can be explained by changes in the probability of crosslinks. Syneresis appeared at relatively low concentrations of calcium.

Characterization of the solid electrolyte AgI—poly (N-hexylene, N′-butylene, N,N,N′,N′-tetramethyldiammonium diiodide) by X-ray diffraction, Raman light diffusion, differential thermal analysis and conductimetric studies

Abstract The total electrical conductivity of the solid electrolyte AgI—poly ( N -hexylene, N ′-butylene, N , N , N ′, N ′-tetramethyldiammonium diiodide), containing 90% of equivalent AgI, is 0.005 (ohm cm) −1 at 25°C. This composition is investigated by X-ray diffraction, Raman light diffusion, differential thermal analysis and conductimetric study. All these studies prove the existence of a new conducting compound.

Conductimetric studies on aqueous solutions of electrolytes. 2. Conductivities of zinc sulfate

Conductimetric studies on aqueous solutions of electrolytes. 2. Conductivities of zinc sulfate

Conductimetric Studies of Ionic Association of Tetraalkylammonium Halides and Tetraphenylborate in N,N-Dimethylformamide–Methyl Ethyl Ketone Mixtures at 25 °C

Abstract The molar conductivities of Et4NBr, n-Pr4NBr, n-Bu4NBr, and n-Bu4NBPh4 have been measured in N,N-dimethylformamide–methyl ethyl ketone (DMF–MEK) mixtures (34.5≥D≥20.10) over the maximum concentration range (2×D3×10−7 mol dm−3) along with the densities and viscosities of the solvent mixtures at 25 °C. The conductance data have been analyzed by using the Fuoss-1978 (F78) conductance equation and the results compared with those obtained from the Justice (J) and the Fuoss-Onsager-Skinner (FOS) equations. The molar conductivities at infinite dilution (Λ0), the thermodynamic association constant (KA) and the distance or the ion-size parameter (R or a°) are evaluated from these data. A better fit of the parameters was provided by the F78 equation which yielded KA and R values. The Λ0 and the KA values are found to increase with decrease in the dielectric constant of the medium and in a given solvent mixture they follow the order Et4NBr&amp;gt;n-Pr4NBr&amp;gt;n-Bu4NBr&amp;gt;n-Bu4NBPh4.