Aqueous Perchlorate Solutions Research Articles

The giant Raman scattering absolute cross-section for light scattered by the silver-adatom-metal complexes at silver electrodes in silver perchlorate aqueous solutions

The value of giant Raman scattering absolute cross-section for silver adatoms (σad = 3.1 × 10−27 cm2/adatom) is determined by the measuring of the background intensity in the giant Raman scattering spectra at silver electrode surfaces in silver perchlorate solutions. With taking into consideration of the sulfate ion specific adsorption, the improved value σad = 1.9 × 10−27 cm2/adatom is determined in silver sulfate solutions. The closeness of the values in the two solutions allows concluding that the weakly adsorbing anions affect but negligibly the silver adatom properties; however, in compliance with the earlier data obtained in sulfate solutions, they affect markedly the kinetics of the adatom migration over electrode surface.

X-ray diffraction study of isomorphous crystal nonahydrates of aluminum, gallium, and scandium perchlorates

Crystal structures of isomorphous crystal nonahydrates of aluminum, gallium, and scandium perchlorates were determined by the X-ray crystal analysis at room temperature. The estimate of associates present in concentrated solutions was carried out by the method of X-ray diffraction in aqueous solutions of aluminum perchlorate.

Poly(3,4-ethylenedioxythiophene methanol)/ascorbate oxidase/nafion-single-walled carbon nanotubes biosensor for voltammetric detection of Vitamin C

Vitamin C (VC) content in commercial juices was voltammetrically determined using a highly selective and sensitive poly(3,4-ethylenedioxythiophene methanol)/ascorbate oxidase/Nafion-single-walled carbon nanotubes (PEDOTM/AO/Nafion-SWCNT) biosensor. The biocompatible PEDOTM matrix was prepared facilely by the one-step electrochemical deposition technique in lithium perchlorate aqueous solutions. AO was dip-coated on the surface of the biocompatible PEDOTM matrix. The mixture of Nafion-SWCNT was dip-cast onto the surface of AO layer when it was obtained by blending Nafion solution and SWCNT dispersion together in a volume ratio of 1:1. The prepared PEDOTM/AO/Nafion-SWCNT biosensor was used for the voltammetric determination of VC, which exhibited the good linear range (4.0 × 10−5−3 × 10−3 mol/L), low detection limit (13 μmol/L), pronounced sensitivity (1.4072 mA (mmol/L)−1 cm−2), high bioaffinity (low apparent Michaelis-Menten constant), good stability (good repeatability), high specificity (good anti-interference ability) coupled with the good reliability and feasibility (the determination of VC in commercial juices). Meanwhile, the good aqueous solubility and the low onset oxidation potential of EDOTM will be more beneficial to the application in biosensor field compared to 3,4-ethylenedioxythiophene. Moreover, the good biocompatibility of PEDOTM matrix and high selectivity of Nafion-SWCNT films also provide a promising platform for the development of biosensing devices.

Re-evaluation of the Thermodynamic Activity Quantities in Pure Aqueous Solutions of Chlorate, Perchlorate, and Bromate Salts of Lithium, Sodium or Potassium Ions at 298.15 K

The Huckel equation used to correlate the experimental activities of dilute alkali metal chlorate, perchlorate or bromate solutions up to a molality of about 1.5 mol⋅kg−1 contains two electrolyte-dependent parameters: B {that is related closely to the ion-size parameter (a∗) in the Debye–Huckel equation} and b1 (this parameter is the coefficient of the linear term with respect to the molality, which is related to hydration numbers of the ions of the electrolyte). In more concentrated solutions up to 7 mol⋅kg−1, an extended Huckel equation was used, it contains additionally a quadratic term with respect to the molality, and the coefficient of this term is the parameter b2. Parameters for the Huckel equations were evaluated from isopiestic data for LiClO3, LiBrO3, LiClO4, NaClO3, NaBrO3, NaClO4, KClO3, and KBrO3. In these estimations, the Huckel parameters determined recently for NaCl solutions were used. The resulting parameter values were tested with the vapor pressure and isopiestic data available in the literature for solutions of these salts. Most of these data were reproduced within experimental error by means of the Huckel or extended Huckel equations, at least up to a molality of 3.0 mol⋅kg−1, for all salts considered. Reliable activity and osmotic coefficients for solutions of these salts can, therefore, be calculated by using the new Huckel equations, and they are tabulated here at rounded molalities. The activity and osmotic coefficients obtained from these equations were compared to the values reported in several previous tabulations.

Laboratory studies of perchlorate phase transitions: Support for metastable aqueous perchlorate solutions on Mars

Perchlorate salts, recently discovered on Mars, are known to readily absorb water vapor from the atmosphere and deliquesce into the aqueous phase at room temperature. Here we study the deliquescence (crystalline solid to liquid transition) and efflorescence (liquid to crystalline solid transition) of perchlorate salts at low temperatures relevant to Mars. A Raman microscope and environmental cell were used to determine the deliquescence relative humidity (DRH) and efflorescence relative humidity (ERH) of NaClO 4 and Mg(ClO 4) 2 as a function of temperature and hydration state. We find that the deliquescence of anhydrous NaClO 4 is only slightly dependent on temperature and occurs at ~ 38% RH. The DRH of NaClO 4·H 2O increases with decreasing temperature from 51% at 273 K to 64% at 228 K. The DRH of Mg(ClO 4) 2·6H 2O also increases with decreasing temperature from 42% at 273 K to 64% at 223 K. The efflorescence of both NaClO 4 and Mg(ClO 4) 2 salt solutions occurs at a lower RH than deliquescence due to the kinetic inhibition of crystallization. For all temperatures studied, the ERH values of NaClO 4 and Mg(ClO 4) 2 are 13% and 19%, respectively. These results indicate perchlorate salts can exist as metastable, supersaturated solutions over a wide range of RH and temperature conditions. Summer diurnal temperature and relative humidity cycles at low latitudes on Mars could allow the surface salts to be aqueous for several hours per day.

A Mechanistic Approach to the Kinetics of Oxidation of Uranium(IV) by Hexachloroplatinate(IV) in Aqueous Perchlorate Solutions. Evidence of the Formation of a Binuclear Intermediate Complex

The kinetics of hexachloroplatinate(IV) oxidation of uranium(IV) ion in aqueous perchloric acid solutions at a constant ionic strength of 1.0 mol dm(-3) has been investigated using the stopped-flow and conventional spectrophotometric techniques. The oxidation reaction was found to proceed through two distinct stages. The initial stage was found to be relatively fast corresponding to the formation of [(H(2)O)(n)U(IV)·Cl(6)Pt(IV)](2+) binuclear intermediate complex (with the rate constant k(1) = 1.75 × 10(4) dm(3) mol(-1)s(-1), k(-1) = 6.8 s(-1), and the formation constant K = 2.6 × 10(3) dm(3) mol(-1) at [H(+)] = 1.0 mol dm(-3) and 25 °C for binuclear formation). This stage was followed by a much slower stage corresponding to the transfer of two electrons from U(IV) to Pt(IV) in the rate-determining step (with the rate constant k = 5.32 × 10(-5) s(-1) at [H(+)] = 1.0 mol dm(-3) and 25 °C). The reaction stoichiometry was found to depend on the molar ratio of the reactants concentration. The experimental results indicated the decrease of the observed first-order rate constants with increasing the [H(+)] for the decomposition of the binuclear intermediate complex through the slow-second stage, whereas no change was observed with respect to the rate of formation of the binuclear complex at the initial rapid part. A tentative reaction mechanism consistent with the kinetic results is discussed.

Solvent extraction of some trace metals and iron with N-Octyl-N,N-bis(dihexylphosphinylmethyl)amine

The processes were studied of the solvent extraction of the ions of triply-charged trace elements including scandium, indium, gallium, and yttrium, as well as iron, with N-octyl-N,N-bis(dihexylphosphinylmethyl) amine solution in toluene, chloroform or methylene chloride from hydrochloric, nitric or perchloric acids aqueous solutions. The metals extraction dependence on the acid concentration showed that the best results were reached using perchloric acid. The calculation of partition coefficients of metals allowed us to reveal a high selectivity of the scandium extraction. The prospects of using the investigated bisphosphinylamine in the technology of extraction, concentration and separation of the trace metals ions was concluded.

Enthalpies of solution and standard enthalpy of formation of crystalline NaVO3 · 2H2O

The enthalpies of solution of sodium metavanadate dihydrate in aqueous solutions of sodium perchlorate at ionic strength I = 0.3, 0.5, and 1.0 mol/L were calorimetrically measured at 298.15 K. The resulting experimental data were used to calculate the standard enthalpy of formation of crystalline NaVO3 · 2H2O.

Kinetics and mechanism of permanganate oxidation of iota- and lambda-carrageenan polysaccharides as sulfated carbohydrates in acid perchlorate solutions

The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm −3 have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that Mn III is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed.

Complexation of U(VI), Ce(III) and Nd(III) with acetohydroxamic acid in perchlorate aqueous solution

Complexes of UO22+, Ce3+ and Nd3+ (M) with acetohydroxamic acid (AHA or L) in an aqueous solution have been investigated by the pH-spectral titration method at 25 °C in an aqueous medium of 1.0 M NaClO4 ionic strength. Cerium(III) and neodymium(III) form [ML]2+, [ML2]+, [ML3] complexes with acetohydroxamic acid, while in case of UO22+ form [UO2L]+, [UO2L2] complexes with acetohydroxamic acid. Data processing with SQUAD program calculates the best values for the stability constants from pH-spectrophotometric titration data. The protonation constant obtained was pK1 = 9.15 ± 0.04 at 25 °C. The stability constants for acetohydroxamic acid with UO22+, Ce3+ and Nd3+ were β1 = 7.22 ± 0.011, β2 = 14.89 ± 0.018 for UO22+ and β1 = 5.05 ± 0.062, β2 = 10.60 ± 0.076, β3 = 16.23 ± 0.088 for Ce3+ and β1 = 5.90 ± 0.028, β2 = 12.22 ± 0.038, β3 = 18.58 ± 0.042 for Nd3+, respectively.

Ionic Strength Dependence of Dioxovanadium(V) Complexation with Ethylene Glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic Acid

Stability constants for the complexation processes of the VO2+ ion with ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) in sodium perchlorate aqueous solutions for ionic strengths between (0.10 and 1.00) mol·dm−3 were calculated at T = 298 K by potentiometric and UV spectroscopic methods. The results indicate that EGTA forms the VO2H3L, VO2H2L−, and VO2HL2− species with the VO2+ ion in the pH range of about 1.00 to 2.50. Different thermodynamic models (extended Debye−Huckel type (EDH), specific ion interaction theory (SIT), and parabolic) have been examined for the ionic strength dependence of the stability and dissociation constants for the above-mentioned species.

Adsorption of Tetramethylthiourea in the Presence of Cationic Detergent at Interface Electrode / Aqueous Perchlorate Solutions

The mixed adsorption layers of tetramethylthiourea and a cationic detergent formed at electrode surface in NaClO4 (1 mol dm -3 ) are described. The systems were characterized by the measurement of dif- ferential capacity, zero charge potential, and surface tension at this potential. The data were analyzed to obtain the surface pressure and relative surface excess of tetramethylthoiurea as a function of electrode charge at bulk concentration of studied compounds. It was stated that the adsorbing tetramethylthoiurea molecule pushed out the water molecule instead of the detergent molecule from the electrode surface. The constants of the Frumkin and corrected Flory-Huggins isotherm point to a decreased TMTU adsorp- tion energy in the cationic detergents presence and stronger repulsive interaction. Electrostatic para- meters of the inner layer were assigned. In the range of more negative potentials, mixed adsorption layers were described by investigating the kinetics of the Zn 2+ ions electroreduction as a piloting ion. (doi: 10.5562/cca1791)

Biomimetic polypyrrole based all three-in-one triple layer sensing actuators exchanging cations

Simultaneous actuation and sensing properties of a triple layer actuator interchanging cations are presented for the first time. Thick polypyrrole (pPy)/dodecylbenzenesulfonate (DBS) films (36 μm) were electrogenerated on stainless steel electrodes. Sensing characteristics of pPy-DBS/tape/pPy-DBS triple layer artificial muscle were studied as a function of electrolyte concentration, temperature and driving current using lithium perchlorate (LiClO4) aqueous solution as electrolyte. The chronopotentiometric responses were studied by applying consecutive square waves of currents to produce angular movements of ±45° by the free end of the triple layer. The evolution of the muscle potential (anode film versus cathode film) during current flow is a function of the studied chemical and physical variables. The electrical energy consumed to describe a constant angle is a linear function of the working temperature or of the driving electrical current, and a double logarithmic function of the electrolyte concentration. Those are the sensing functions. The cation exchanging bending triple layer actuator senses the working conditions. Similar sensing functions were described in the literature for devices interchanging anions. Irrespective of the reaction mechanism, a single electrochemo–mechanical device comprised of two reactive polymer electrodes (oxidation film and reduction film) works simultaneously as both sensor and actuator (self-sensing actuators). These are the general sensing properties of dense and biomimetic reactive gels of conducting polymers. Thus, any reactive device based on the same type of materials and reactions (batteries, smart windows, actuators, electron–ion transducers) is expected to sense surrounding conditions, as biological organs do.

Perchlorate anion on manganese(III) porphyrin as an ATR-IR probe for nanoscopic water environments

The effects of aqueous environments on the perchlorate infrared lineshape were investigated in various ionic solutions, including a polymeric polyvinyl chloride membrane and perchlorate coordinated to manganese(III) porphyrin, using the model frequency–frequency correlation function (FFCF). The perchlorate ligand moiety is considered a useful infrared probe in aqueous nanoscopic environments. We observed an asymmetric mode of the ligated perchlorate, in which the lineshape had a smaller bandwidth and faster dynamics than that of a 1 M perchlorate aqueous solution. In the 6 M solutions, we observed at least two conformations with faster dynamics than that of the 1 M solution, regardless of whether it was in the heterogeneous polymer matrix.

Acid-catalyzed oxidation of some sulfated polysaccharides: Kinetics and mechanism of oxidation of kappa-carrageenan by cerium(IV) in aqueous perchlorate solutions

The kinetics of oxidation of kappa-carrageenan (KCAR) as a sulfated polysaccharide by cerium(IV) in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm −3 have been investigated, spectrophotometically. The results showed a first-order dependence in [Ce IV] and fractional-first-order kinetics in carrageenan concentration. A kinetic evidence for the formation of 1:1 complex has been revealed. The hydrogen ion dependence of the reaction rate indicated that the oxidation process is acid catalyzed. The oxidation product was identified by the spectral data and elemental analysis. The activation and thermodynamic parameters have been evaluated and a relevant reaction mechanism is suggested and discussed.

Effect of external magnetic fields on electron transfer and ion pairing dynamics at ferrocenyl alkane thiol SAM/solution interfaces

The redox behavior of ferrocene alkane thiol self assembled monolayer modified electrodes in contact with aqueous perchlorate solutions both in the absence of and in the presence of an external magnetic field is examined using both electrochemical and gravimetric techniques The redox switching process involves an ET reaction involving the ferrocene/ferricinium redox transition coupled with an ion pairing step involving perchlorate ion. The voltammetric response recorded in the latter medium is irreversibly affected by the imposition of a static magnetic field of magnitude 0.5 T applied in a direction parallel to the electrode surface. The magnetic field dependence of the redox behavior is attributed to structural changes in the monolayer arising from double layer effects involving changes in the spatial distribution of perchlorate counterions at the monolayer/solution interface, brought about by local convective stirring arising from the B field generated magnetohydrodynamic Lorenz body force.

ChemInform Abstract: Kinetics and Mechanism of Oxidation of Tin(II) by Hexachloroiridate(IV) in Aqueous Perchlorate Solutions

The kinetics of hexachloroiridate(IV) oxidation of tin(II) in aqueous perchlorate media at a constant ionic strength of 2.0 mol dm -3 have been studied spectrophotometrically. The reaction was found to follow second-order overall kinetics and first order with respect to each of the reactants. The results showed hydrogen ion dependence where the reaction rate increased with increasing hydrogen ion concentration. The activation parameters were evaluated and a tentative reaction mechanism has been discussed.

Kinetics and Mechanism of Oxidation of Nicotine by Permanganate Ion in Acid Perchlorate Solutions

The kinetics of permanganate oxidation of nicotine alkaloid in aqueous perchlorate solutions at a constant ionicstrength of 1.0 mol dm-3 have been investigated spectrophotometrically. The kinetic results showed first-orderkinetics in permanganate and fractional-first-order dependence with respect to nicotine concentration. Theinfluence of hydrogen ion concentrations on the reaction rate showed inverse first-order kinetics in [H+] wherethe oxidation rates were increased with decreasing hydrogen ion concentration. A kinetic evidence for theformation of 1:1 complex has been revealed. The ionization constant of nicotine was calculated from the kineticdata and was found to be 9.69x10-4 mol dm-3 at ionic strength of 1.0 mol dm-3 and 25o C. The kinetic parametershave been evaluated and a tentative reaction mechanism consistent with the kinetic results is discussed.

ChemInform Abstract: Raman Spectroscopic Measurements of Scandium(III) Hydration in Aqueous Perchlorate Solution and ab initio Molecular Orbital Studies of Scandium(III) Water Clusters: Does Sc(III) Occur as a Hexaaqua Complex?

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Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution

The mechanism for hydrogen bond (H-bond) switching in solution has remained subject to debate despite extensive experimental and theoretical studies. We have applied polarization-selective multidimensional vibrational spectroscopy to investigate the H-bond exchange mechanism in aqueous NaClO4 solution. The results show that a water molecule shifts its donated H-bonds between water and perchlorate acceptors by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extracted an average jump angle of 49 +/- 4 degrees, in qualitative agreement with the jump angle observed in molecular dynamics simulations of the same aqueous NaClO4 solution.