Perchloric Acid Concentration Research Articles

Electrochemical oxidation of squaric and croconic acids on Pt and Pt surfaces modified by underpotential heavy metal monolayers in acid solutions

The electrochemical oxidation of squaric and croconic acids on platinum in aqueous perchloric acid solutions has been investigated by means of cyclic voltammetry, rotating disc electrode, potentiostatic transients and controlled-potential electrolysis. The kinetic parameters (Tafel slopes, reaction orders) have been determined on the foot of the wave by varying the sweep rate, the angular velocity, depolarizer concentration, and perchloric acid concentration. A probable mechanism has been proposed for the overall oxidation processes. It involves two charge-transfer steps followed by the desorption of product, which is the rate-determining step. The oxidation product is immediately deactivated by a rapid hydration reaction. Also, the effect of underpotential Tl, Pb, and Bi monolayers on the electrochemical behaviour of squaric and croconic acids has been examined.

New aspects of the electrochemistry of heteropolyacids: Part II. Coupled electron and proton transfers in the reduction of silicoungstic species

The reduction process of silicotungstic species has been studied by cyclic voltammetry in strongly acidic aqueous solutions and in dimethylformamide with stepwise addition of perchloric acid. Important morphology changes of the waves are observed in these media. In particular, attention has been focused on the first voltammetric wave which rises from a one-electron, diffusion-controlled process to an overall, apparently direct, two-electron transfer in the range of 3 M to 7 M perchloric acid concentration in water. In large-scale electrolysis on this two-electron wave, hydrogen evolution is observed. Due to solvent effects, much the same phenomena are obtained in dimethylformamide, except that it is not necessary to resort to such extreme perchloric acid concentrations to reach the two-electron process. In this last medium, the behaviours of H 4SiW 12O 40 and H 4SiW 12O 40 have been compared. Hydrogen evolution during electrolysis on the two-electron wave in dimethylformamide has also been observed. A clear difference appears between the mechanisms of formation of the two-electron wave in acidic water and in dimethylformamide. In the former case, the second wave shifts in the positive direction until it merges with the first one, while in the latter medium a new wave more positive than the original waves grows at their expense. These observations are explained on the basis of solvent effects.

Mise en evidence de deux nouveaux indicateurs acide-base dans l'acide acetique anhydre

The behaviour of two organic compounds, 1,5-di[2-furyl]-1,4-pentadien-3-one (DFPO) and 1,5-di[2-thienyl]-1,4-pentadien-3-one (DTPO), as acid-base indicators has been studied by plotting the curves A = f(λ) in the presence of various concentrations of perchloric acid, in anhydrous acetic acid medium. The values of p K i HClO 4 ) have been determined by spectrophotometry. The efficiency of these indicators in visual and colorimetric detection of the end-points of acid-base titrations has been examined.

Perchloric acid interference in enzymatic-fluorimetric-continuous-flow assay methods for measuring glucose, lactate, pyruvate, alanine, glycerol, and 3-hydroxybutyrate in blood.

Perchloric acid is commonly used to denature and precipitate proteins in samples before various metabolites are measured in tissue, blood, and other body fluids. However, perchloric acid can interfere in the analytical process, possibly by inhibiting the enzymes used. We have determined the effects of perchloric acid on measurements of glucose, lactate, pyruvate, alanine, glycerol, and 3-hydroxybutyrate in blood by enzymatic-fluorimetric-continuous-flow assays. There was a net increase or decrease in the apparent concentration of some of these metabolites when the perchloric acid concentration in the samples differed from that of the reference standards-some of these differences were due to the concentration of perchlorate ion and some to the pH of the acid extracts. The results show the need either to add a fixed amount of blood to perchloric acid or to neutralize and remove the perchlorate.

Kinetics of oxidation of bis(ethylenediamine)mercaptoacetatocobalt(III) and cysteinatobis(ethylenediamine)cobalt(III) ions by peroxodisulphate in aqueous-nonaqueous mixed solvents

The kinetics of oxidation in the first step was studied for coordination-bonded sulphur in the cysteinatobis(ethylenediamine)cobalt(III) and bis(ethylenediamine)mercaptoacetatocobalt(III) ions using peroxodisulphate as oxidant. The effect of the acid-base equilibria of the reactants was established based on the dependences of the rate constant and the thermodynamic activation parameters ΔH and ΔS on perchloric acid concentration. The effect of ionic strength at various perchloric acid concentrations, was examined for the two complex ions. The combined effect of perchloric acid and sodium perchlorate was investigated in water-tert-butyl alcohol and water-ethylene glycol solutions. The transfer functions were calculated from the changes in the solubility of the reactants on passing from aqueous to the mixed aqueous-nonaqueous solutions, and the role of solvation during the oxidation of the complexes by peroxodisulphate was assessed based on the dependences of the transfer functions on the nonaqueous component content of the solvent system.

Kinetics of oxidation of bis(ethylenediamine)mercaptoacetatocobalt (III) ion by periodate in water-t-butanol and water-methanol mixtures at different perchloric acid concentrations

The kinetics of oxidation of the bis(ethylenediamine)mercaptoacetatocobalt (III) ion by periodate were investigated as a function of perchloric acid concentration, ionic strength and temperature. Furthermore, the effect of a nonaqueous component of the solvent on the rate constant and activation parameters ΔH≠ and ΔS≠ in the water-t-butanol and water-methanol mixtures was estimated. The solvent effect is discussed from the viewpoint of the change in solvation of initial and transition states on going from water to a mixed solvent.

Factors affecting determination of delta-aminolevulinate by use of Ehrlich's reagent.

We investigated the formation of delta-aminolevulinic acid (ALA)-pyrrole and subsequent color development used in determining ALA in urine. Of three condensation reagents examined--acetylacetone, ethyl acetoacetate, and methyl acetoacetate--the last was the best. When the ALA-pyrrole is reacted with Ehrlich's reagent in ethyl acetate according to one procedure, the optimum concentration of perchloric acid in the reagent is 0.5 to 1.0 mol/L. Its optimum concentration is 1.0 to 2.3 mol/L when the reaction takes place in water.

Acid-catalyzed iodination of a hindered alkyl aryl ketone: 2,4,6-trimethylacetophenone ( [formula omitted]). rate dependence on iodine concentration

Rates of the perchloric and hydrochloric acid-catalyzed reactions of iodine with the title ketone ( 1 ) in 50% aqueous acetic acid at constant ionic strength were studied by following the decrease in iodine concentration at 353 nm. The rates were first order in iodine at concentrations up to about 6 × 10 -5 M and first order in ketone oncentration. A slight decrease in rate with increase in iodine concentration was attributed to complexation of iodine with the carbonyl oxygen. The effect of perchloric acid concentration on the rate was studied; a plot of k vs. [HClO 4] was bell-shaped with a maximum at about 9 × 10 -3 M. Reversibility of the iodination reaction is suggested. Explanations are proposed for anomalous results observed in the effect of iodide concentration on the rate. E a for the iodination reaction (82 kJ mol -1) is higher than that for bromination of 1 in accord with the order for halogenation of other organic substrates.

Vinyl polymerization of acrylamide initiated by Thallium(III) ions in solution

AbstractKinetics of polymerization of acrylamide initiated by Thallium(III) perchlorate was investigated in aqueous perchloric acid medium in the temperature range of 55–70°C. The rates of polymerization were measured varying the concentration of the monomer, initiator, and perchloric acid. The rate of polymerization was found to increase with increase of temperature, monomer concentration, initiator concentration, and perchloric acid concentration. The effect of additives like different solvents, surfactants, and retarders on the rate of polymerization was studied. Molecular weights of the polymer were determined by viscometry. The chain transfer constants for the monomer (CM) and that for the solvent dioxan (Cs) were calculated to be 7.33 × 10−3 and 6.66 × 10−3, respectively. From the Arrhenius plot, the overall activation energy (Ea) was calculated to be 10.68 kcal/mol. The energy of initiation was calculated to be 12.36 kcal/mol. Depending on the results obtained, a suitable reaction mechanism has been suggested and a rate equation has been derived.

ChemInform Abstract: PREPARATION, PROPERTIES, AND ANALYTICAL APPLICATIONS OF CRYSTALLINE TIN(IV) TUNGSTOSELENATE

AbstractSn(flVW‐Vvolframatoselenat wird aus SnCl4‐ 5 H2O, Na2SeO3 und Na2WO4‐ 2 H2O in unterschiedlichen Mischungsverhältnissen und bei unterschiedlichen pH‐Werten (Bedingungen tabellarisch angegeben, keine Ausb.) dargestellt.

Kinetics of oxidation of pentaammine-isothiocyanato-cobalt(III) ion with peroxodisulphate and periodate in water and water-organic mixtures

The kinetics of oxidation of [Co(NH3)5(NCS)]2+ by peroxodisulphate and periodate were investigated at different ionic strengths, and at different temperatures and concentrations of perchloric acid. Rate constants and activation parameters are also reported in mixed water-organic solvents. It was shown that the acid-base equilibria involving S2O8−2, and IO4− ions are important in the reactions studied. Solvent effects on the oxidation are interpreted in terms of the solvation of both the initial state and the activated complex.

Separation of vanadium-48 from a deuteron-irradiated TiO2 target

The influence of perchloric acid and hydrogen peroxide concentrations on the elution rates of vanadium and titanium from Dowex-50W X 8 resin was studied. The amounts of perchloric acid and of hydrogen peroxide were adjusted to provide an optimum eluent for the separation of vanadium from the irradiated titanium (TiO2) target.

Preparation, Properties, and Analytical Applications of Crystalline Tin(IV) Tungstoselenate

Abstract Synthesis of tin(IV) tungstoselenate has been done under a variety of conditions. The effects of mixing ratio of reagents and the pH of the mixture on the properties of the material have been studied. The crystalline sample of tin(IV) tungstoselenate has been chosen for detailed studies, such as chemical and thermal stabilities, chemical composition, pH-titrations, IR and X-ray analyses. On the basis of above studies a tentative formula has been proposed for tin(IV) tungstoselenate. The adsorption behaviour of metal ions in different concentrations of perchloric acid has been studied. On the basis of Kd values few analytically important separations of metal ions have been achieved on small columns of tin(IV) tungstoselenate.

A re-evaluation of conditions required for an accurate estimation of the extramitochondrial [formula omitted] ratio in isolated rat-liver mitochondria

The values reported in the literature for the extramitochondrial ATP ADP ratio in resting rat-liver mitochondria (State 4) vary widely. The conditions required for an accurate determination of this parameter were therefore investigated. (1) In experiments with rat-liver mitochondria incubated under State-4 conditions, it was found that the extramitochondrial ATP ADP ratio, as calculated from the values measured in neutralised perchloric acid extracts, was lower than that estimated from the concentrations of creatine and creatine phosphate, using the metabolite indicator method. The discrepancy is due to hydrolysis of ATP occurring in the presence of perchloric acid. (2) Conditions are described for minimising ATP hydrolysis in the presence of perchloric acid, and include the use of low concentrations of perchloric acid, short times of exposure to the acid before neutralisation, low temperatures and the presence of excess EDTA. Under these conditions, the values obtained for the extramitochondrial ATP ADP ratio agreed with those calculated by the metabolite indicator method, provided ratios do not exceed the value of 100. (3) In cases where the extramitochondrial ATP ADP does exceed 100, phenol/chloroform/isoamyl alcohol must be used to quench the reactions, as described by Slater et al. (Slater, E.C., Rosing, J. and Mol, A. (1973) Biochim. Biophys. Acta 292, 534–553). With this method, the extramitochondrial ATP ADP ratio was found to have a value of more than 1000 in rat-liver mitochondria incubated with succinate + rotenone in the resting state (pH 7.0; T = 37°C), in agreement with Slater et al.

Electrochemical generation of manganese(III) and behaviour of the generated oxidant in acetic acid in the presence of perchlorate ions

Research was carried out to determine conditions for the anodic generation of manganese(III) with high current efficiency in solutions of sodium perchlorate in acetic acid, and to examine the behaviour of the oxidant thus generated. The effects of water and acetic anhydride on current efficiency in the generation of the oxidant was also examined. The formal redox potential of the Mn(III)/ Mn(II) system is decreased with increasing concentrations of sodium acetate in the solution. The effect of sodium perchlorate and perchloric acid concentrations is the reverse. Procedures for coulometric titrations of a number of substances with the generated oxidant were developed, end point being detected using biamperometric and potentiometric methods. Perchloric acid accelerates the oxidation of certain substances with manganese(III) in acetic acid and increases the sensitivity of end-point detection using the potentiometric method.

Extraction of Hg/II/ with dibutylester of N-/4-antipyryl/-amidophosphoric acid from iodide solutions

A new extraction reagent-dibutylester of N-/4-antipyryl/-amidophosphoric acid/DBAAP/—has been developed and used for the extraction of divalent mercury into chloroform from mixture of sodium iodide and perchloric acid. It was found that the composition of the species extracted into the organic phase depends on the acidity of the aqueous phase. The solvate HgI2. DBAAP is extracted at low HClO4 concentrations, an ion-pair, /DBAAPH/+.HgI 3 − , is formed and extracted at high concentrations of perchloric acid.

Spectrophotometric determination of cobalt with cyclohexane-1, 2-dione bis(2-pyridylhydrazone)

A method for the spectrophotometric determination of cobalt with cyclohexane-1,2-dione bis(2-pyridylhydrazone) is described. The pink complex is formed at an initial pH of 4–5 in a medium containing 12%V/V dimethylformamide, and the absorbance is measured at 525 nm at a final perchloric acid concentration of ca. 0.5 M. The molar absorbtivity is 13700 l mol–1 cm–1. The method has been applied to the determination of cobalt in alloys and minerals.

Solvent effects on the kinetics of oxidation of cysteinatobis(ethylenediamine)cobalt(III) ion by peroxodisulphate

The kinetics of oxidation of cysteinatobis(ethylenediamine)cobalt(III) ion, [Co(CysOS)(en)2]+, by peroxodisulphate were investigated at different ionic strengths, adjusted with various electrolytes, and at different temperatures and concentrations of perchloric acid. Rate constants and activation parameters are also reported for this oxidation in mixtures containing up to 40% acetone, t-butyl alcohol, isopropyl alcohol, or acetonitrile. The solubilities of [Co(CysOS)(en)2]ClO4 and KClO4 have been determined in water and aqueous acetone and aqueous t-butyl alcohol at 298.2 K. From these values, Gibbs free energies of transfer for [Co(CysOS)(en)2]+ and S2O82– have been estimated. The solvent effects on the oxidation have been divided into their initial-state and transition-state components.

Reaction of N-heteroaromatic bases with nitrous acid. Part 8. Kinetics of the diazotisation of 1-methyl- and 1-methoxy-4-aminopyridinium perchlorate in aqueous perchloric acid

The diazotisation of 1-methyl-4-aminopyridinium perchlorate in 0.25–5.00M-perchloric acid is of first order in both the amine and nitrous acid. The rate coefficients increase with an increase in the concentration of perchloric acid and sodium perchlorate. In perchloric acid solutions whose ionic strength is maintained constant by the addition of sodium perchlorate the rate coefficients of the diazotisation of 1-methyl- and 1-methoxy-4-aminopyridinium perchlorate show a rectilinear dependence on the ho parameter of the medium. It is suggested that the reaction involves an initial interaction between the nitrosating agent and the heteroaromatic nucleus of the 1-methyl- or the 1-methoxy-4-aminopyridinium ion. pKa Values are recorded.

Vinyl Polymerization of Ethyl Acrylate Initiated by TI3+-Ascorbic Acid Redox System

Abstract Thallium(III) perchlorate alone was found to be ineffective as an initiator for the vinyl polymerization of ethyl acrylate. However, in the presence of the activator ascorbic acid, the redox system T13+ -ascorbic acid was found to initiate polymerization. The kinetics of polymerization of ethyl acrylate initiated by the T13+-ascorbic acid redox system was investigated in aqueous perchloric acid medium in the temperature range 55–70°C in the presence of oxygen. The rate of polymerization was evaluated by varying the concentrations of ethyl acrylate, T13∗, ascorbic acid, and perchlorid acid. The rate of polymerization was found to increase steadily with an increase of monomer concentration, T13+ concentration, ascorbic acid concentration, and perchloric acid concentration. The effects of additives such as organic solvents, different surfactants, and inhibitors on the initial rate of polymerization were investigated. Molecular weights and chain length of the purified polymer were determined by viscom-etry. Chain transfer with various solvents was studied and the chain transfer constants were calculated to be 0.13 × 104 for methanol, 0.43 × 104 for dioxane, and 0.69 × 104 for acetone. From the Arrhenius plot the overall activation energy wass found to be 6.82kcal/mol. A suitable kinetic scheme has been proposed and a rate equation has been derived.