Chlorate Ions Research Articles

Problems Associated with the Electrochemical Reduction of Metal Ions in LiNO3 ‐ KNO 3 and LiClO4 ‐ KClO4 Melts: The Reduction of Nitrato and Perchlorato Complexes

Electrochemical studies of Ag+, Tl+, Cd++, Pb++, Zn++, and In+++ metal ions on platinum electrodes in molten show that only silver ions are readily reduced to the metal within the electrostability region of the melt. The other metal ions form nitrato complexes that are reduced directly to the metal oxide at potentials less negative than solvent reduction. For divalent metal ions, these reactions can be represented by . Scission of the O‒N bond likely occurs in the first electron transfer step. The atomic absorbance analysis of a mercury cathode used in the exhaustive electrolysis of Cd++ ions provided substantial evidence that the deposition of cadmium metal does not occur in the melt. Investigations of Cd and Zn metals and amalgams show that the much faster electrode reactions occur at considerably more negative potentials than the cathodic wave produced by the addition of these metal ions to nitrate melts. The controversial water wave in nitrate melts can be explained by the analogous reduction of the complex to OH− and . Studies of Pb++ and In+++ metal ions in melts give similar results that suggest the formation of perchlorato complexes that are reduced to the metal oxide and chlorate ions.

Kinetics and mechanism of anodic oxidation of chlorate ion to perchlorate ion on lead dioxide electrodes

The kinetics and mechanism of anodic oxidation of chlorate ion to perchlorate ion on titanium-substrate lead dioxide electrodes have been investigated experimentally and theoretically. It has been demonstrated that the ionic strength of the solution has a marked effect on the rate of perchlorate formation, whereas the pH of the solution does not influence the reaction rate. Experimental data have also been obtained on the dependence of the reaction rate on the concentration of chlorate ion in the solution at constant ionic strength. With these data, diagnostic kinetic criteria have been deduced and compared with corresponding quantities predicted for various possible mechanisms including double layer effects on electrode kinetics. It has thus been shown that the most probable mechanisms for anodic chlorate oxidation on lead dioxide anodes involve the discharge of a water molecule in a one-electron transfer step to give an adsorbed hydroxyl radical as the rate-determining step for the overall reaction.

Anion uptake in maize roots: Interactions between chlorate and nitrate

Effects of nitrate, chloride and chlorate ions upon nitrate and chlorate uptake by roots of maize (Zea mays L., cv. B73) seedlings were examined. Net nitrate uptake, 36ClO3− influx and 36Cl− influx (the latter two in a background of 0.5 mM KNO3) displayed similar pH profiles with optima at pH 5.5 and below. External, non‐labeled chloride had little effect on the accumulation of 36ClO3− (both in 5 h and 20 min uptake assays), while nitrate and chlorate had almost identical, marked inhibitory effects. Nitrate pretreatment caused an apparent induction of both 36ClO3− and 15NO3− uptake activities. After 5 h of treatment in nitrate, the uptake activities of chloride‐ and chlorate‐pretreated plants increased to that of nitrate‐pretreated plants. During 6 h exposure to chlorate, 36ClO3− uptake activity of nitrate‐pretreated plants decreased to that of chlorate‐ and chloride‐pretreated plants. The results support the existence of a shared nitrate/chlorate transport system in maize roots which is not inhibited by external chloride, and which is induced by nitrate, but not by chlorate or chloride. The suggestion is made that selection of chlorate‐resistant mutants of maize can identify nitrate uptake as well as nitrate reductase mutants.

Selective chlorine dioxide determination using gas-diffusion flow injection analysis with chemiluminescent detection

An automated chemiluminescent technique has been developed utilizing the advantages of gas-diffusion flow injection analysis. A gas-diffusion membrane separates the donor (sampling) stream from the acceptor (detecting) stream and removes ionic interferences. A novel chemiluminescence flow-through detector cell is used to measure the concentration of chlorine dioxide as a function of the intensity of the chemiluminescence produced from its reaction with luminol. The chemiluminescent reagent merges with the analyte directly in front of the photomultiplier tube in order to maximize the sensitivity of the system. The detection limit for chlorine dioxide is approximately 5 ppb. The method is over 1500 times more selective for chlorine dioxide than for chlorine on a mole basis. This method eliminates interference from iron and manganese compounds, as well as other oxychlorinated compounds such as chlorite ion and chlorate ion.

Removal of By‐products of Chlorine and Chlorine Dioxide at a Hemodialysis Center

Because it is a strong oxidant that does not form trihalomethanes, chlorine dioxide is becoming a popular alternative to chlorine for disinfecting domestic water supplies. However, when water disinfected with chlorine dioxide is used in hemodialysis therapy, care must be taken to ensure adequate removal of all oxidants that could adversely affect the patient. This case study examines the efficiency of water treatment processes typically used at dialysis centers for removing chlorine dioxide, chlorine, and their residual oxidants. Initial data showed that chlorite ion and free chlorine were effectively removed, but because chlorine dioxide and chlorate ion could not be conclusively identified in the water supply to the clinic or in the final product water of the treatment train, their removal could not be determined.

ChemInform Abstract: Reduction of Chlorate and Perchlorate Ions at an Active Titanium Electrode.

AbstractThe electrochemical reduction of Cl04‐ at an active Ti electrode in aqueous 1.0 M HClO4 yielding C1′ occurs by oxygen atom transfer to the Ti surface and not by a pathway involving catalysis by soluble Ti corrosion products.

The reduction of chlorate and perchlorate ions at an active titanium electrode

Perchlorate ion is electrochemically reduced to chloride ion at an active titanium electrode in aqueous 1.0 M HClO 4. The reduction occurs by direct reaction at the surface rather than a pathway involving catalysis by soluble titanium corrosion products. The reaction occurs by oxygen atom transfer to the titanium surface, and the implications of this mechanism for the surface composition of active titanium electrodes are discussed. Chlorate ion is also reduced at titanium, and the rate constant for chlorate reduction is at least 10 5 times greater than that for perchlorate reduction.

Uptake of chlorate and other ions in seedlings of the nitrate‐uptake mutant B1 of Arabidopsis thaliana

The accumulation of labelled ions was measured in seedlings of Arabidopsis thaliana (L.) Heynh. grown in submerged cultures. Genotypes used were wild type and the nitrate‐uptake mutant B1, which is altered in the uptake of nitrate and chlorate from concentrations above 1 mM when grown under normal conditions. At low and high concentrations of chlorate, chloride, and K+, significantly less radioactivity was accumulated in seedlings of B1 than in seedlings of wild type. The influx of sulphate did not decrease in B1. The results indicate that the effect of the mutation in B1 is restricted to the uptake of monovalent ions.

Selectivity enhancement by flow injection analysis

Flow injection analysis offers numerous possibilities for significantly increasing the selectivity of existing methods by utilizing knowledge of the chemistry of those methods. It also enables new selective methods to be created by utilizing kinetic methods and fast separation techniques such as gas diffusion, dialysis, extraction and ion-exchange columns. Selectivity enhancements and increased sensitivity can be achieved by incorporating the kinetic techniques of kinetic discrimination and/or kinetic enhancement into the timing of the system or the reagent concentrations and conditions for a given method. Methods have been developed for quantifying ozone, chlorine dioxide, chlorate ion, and chlorite and chlorate ions sequentially. A dual-phase gas diffusion system for hydride generation provides significant decreases in the interferences observed for transition metals.

Cyclopentane-1,3-dione bis(4-methylthiosemicarbazone) monohydrochloride as a spectrophotometric reagent for the determination of chlorate in perchloric acid medium

1,3-Cyclopentanedione bis(4-methylthiosemicarbazone) monohydrochloride produces colored solutions with chlorate ions in strongly acid medium. The yellow color obtained has been used to propose a spectrophotometric method of C10 3 − determination in the concentration range 0.5–6.0 ppm (molar absorptivity 1.26 × 10 4 liters mol −1 cm −1 at a wavelength of 397 nm).

Application of Factor Analysis to the Analysis of the Kinetics and Mechanism of the X-Ray-Induced Decomposition of Potassium Perchlorate

Factor analysis has been applied to the analysis of the x-ray-induced decomposition of sodium Perchlorate, which yields chlorate and chloride as products. The analysis indicates that the chlorate ion cannot be an intermediate in the perchlorate-to-chloride reduction, as has been reported. A new mechanism consistent with the analysis and rate data for the decomposition are discussed.

Automated iodometric method for determination of trace chlorate ion using flow injection analysis

Deux methodes de dosage de l'ion chlorate a des teneurs respectives de 1.10 −5 M et 1.10 −6 M qui utilisent toutes deux la reaction de l'ion chlorate avec l'ion iodure pour former de l'iode

ChemInform Abstract: CATALYTIC EFFECTS OF CHLORATE IONS ON THE ELECTRODE REACTION PROCESSES OF 12‐MOLYBDOPHOSPHATE AND 12‐MOLYBDOSILICATE

AbstractIn den cyclischen Voltammogrammen der beiden Heteropoly‐Anionen ist die jeweils 3. kathodische Welle, die der Reduktionsstufe vom 4‐Elektronen‐ zum ö‐Elektronen‐Reduktionsprodukt entspricht, in Gegenwart von ClOg‐Ionen ihrer Natur nach katalytisch.

Lower Detection Limits Found for Chlorine Dioxide Contaminants

Disinfecting water with chlorine dioxide eliminates trihalomethane formation but generates several contaminants of its own. Government regulations under consideration would require the removal of these by‐products to levels for which no detection methods have existed. Chemists at the Miami University of Ohio have developed a method to measure chlorate, chlorite, and hypochlorite ions at levels of less than 1 mg/L. The detection accuracy range is ±3 percent.

Electrocatalytic reduction of oxo anions by aqueous molybdenum-catechol complexes

The electrocatalytic reduction of nitrite, chlorate and bromate ions by monomeric molybdenum-catechol complexes has been investigated by dc polarography and cyclic voltammetry in pH 8–10 catechol buffers. The Mo(V) and Mo(IV) complexes. MoO(Hcat)(cat) 2 2− and Mo(cat) 3 2− , produced by one- and two-electron reduction of MoO 2 (cat) 2 2− are catalytically active, but the Mo(III) complex, Mo(cat) 3 3− , is not. This sequence of reactivities among molybdenum oxidation states leads to peak-shaped electrochemical responses characteristic of catalytic chemical reactions coupled between consecutive charge transfers. Apparent second-order rate constants in 1 M KCl, 0.15 M catechol, pH 9.4 are 11.1±0.6, 1.19±0.06 and 460±45 M −1 s −1 for reactions of MoO(Hcat)(cat) 2 2− and 85±10, 30±2 and 2700±300 M −1 s −1 for reactions of Mo(cat) 3 2− with NO 2 − , ClO 3 − and BrO 3 − , respectively. A mechanism is proposed for oxo anion reduction by MoO(Hcat)(cat) 2 2− . Substrate first binds to the Mo(V) center at a coordination site created by dissociation of monodentate catechol (Hcat − ). The unshared electron pair on the central atom of the substrate is implicated in this process because anions which lack this structural feature (NO 3 − and ClO 4 − ) are catalytically inactive. We propose that the N-, Cl- or Br-bonded substrate then rearranges to an O-bonded form which undergoes rapid oxygen atom/electron transfer to produce MoO 2 (cat) 2 2− and reduced product. Similar mechanistic features are indicated for catalysis by Mo(cat) 3 2− . Mo(cat) 3 3− apparently is a kinetically inert d 3 transition metal complex which does not readily undergo the ligand dissociation and substrate coordination reactions that are prerequisite to electron transfer. The significance of these findings is discussed in light of previous observations of Mo-catalyzed oxo anion reductions.

Electrocatalytic reduction of oxo anions by aqueous molybdenum-catechol complexes

The electrocatalytic reduction of nitrite, chlorate and bromate ions by monomeric molybdenum-catechol complexes has been investigated by dc polarography and cyclic voltammetry in pH 8–10 catechol buffers. The Mo(V) and Mo(IV) complexes. MoO(Hcat)(cat) 2 2− and Mo(cat) 3 2−, produced by one- and two-electron reduction of MoO 2(cat) 2 2− are catalytically active, but the Mo(III) complex, Mo(cat) 3 3−, is not. This sequence of reactivities among molybdenum oxidation states leads to peak-shaped electrochemical responses characteristic of catalytic chemical reactions coupled between consecutive charge transfers. Apparent second-order rate constants in 1 M KCl, 0.15 M catechol, pH 9.4 are 11.1±0.6, 1.19±0.06 and 460±45 M −1 s −1 for reactions of MoO(Hcat)(cat) 2 2− and 85±10, 30±2 and 2700±300 M −1 s −1 for reactions of Mo(cat) 3 2− with NO 2 −, ClO 3 − and BrO 3 −, respectively. A mechanism is proposed for oxo anion reduction by MoO(Hcat)(cat) 2 2−. Substrate first binds to the Mo(V) center at a coordination site created by dissociation of monodentate catechol (Hcat −). The unshared electron pair on the central atom of the substrate is implicated in this process because anions which lack this structural feature (NO 3 − and ClO 4 −) are catalytically inactive. We propose that the N-, Cl- or Br-bonded substrate then rearranges to an O-bonded form which undergoes rapid oxygen atom/electron transfer to produce MoO 2(cat) 2 2− and reduced product. Similar mechanistic features are indicated for catalysis by Mo(cat) 3 2−. Mo(cat) 3 3− apparently is a kinetically inert d 3 transition metal complex which does not readily undergo the ligand dissociation and substrate coordination reactions that are prerequisite to electron transfer. The significance of these findings is discussed in light of previous observations of Mo-catalyzed oxo anion reductions.

Catalytic Effects of Chlorate Ions on the Electrode Reaction Processes of 12-Molybdophosphate and 12-Molybdosilicate

Abstract The third cathodic waves corresponding to the reduction processes from the four-electron to the six-electron reduction products of both 12-molybdophosphate and 12-molybdosilicate are catalytic in nature in the presence of chlorate ions. The six-electron reduction product of 12-molybdophosphate is oxidized by chlorate ions more rapidly than that of 12-molybdosilicate.

Iodometric method for determination of trace chlorate ion

Iodometric method for determination of trace chlorate ion

Structural studies of matrix-isolated alkali metal chlorates; an example of tridentate co-ordination by the chlorate ion

The vapours from heated alkali metal chlorates isolated in nitrogen and argon matrices have been studied by infrared spectroscopy. The use of 16O–18O partial isotopic substitution demonstrates the presence of a C3 axis for the molecule CsClO3 isolated in an argon matrix. This is interpreted as the ClO3– ion showing a tridentate interaction with the caesium ion.

Differential-pulse polarographic determination of traces of titanium in solar grade silicon

The proposed method for the determination of Ti in solar grade silicon is based on the catalytic activity of titanium(IV) in presence of chlorate ions. In acidic oxalate solution containing chlorate, titanium(IV) gives an exceptionally high polarographic current owing to its catalysed electroreduction and the well-shaped polarographic wave is suitable for trace analysis.