Mechanism of 2-quinizarinsulphonic acid reduction on a mercury electrode

The reduction of the 1,4-dihydroxyanthraquinone-2-sulphonic acid (quinizarinsulphonic acid) at a dropping mercury electrode has been investigated. The reduction takes place in two monoelectronic steps and show E1/2 values vs. sce (E1/2)1 = −0.380 V and (E1/2)2 = −1.045 V at pH 4.60. The first wave is diffusion controlled, while the second wave is kinetically controlled. The reagent captures one electron and one proton to form the semiquinonic system. The semiquinone is dimerized. The dimer captures one electron and one proton, per molecule, to form the hydroquinone. The reaction orders, together with Tafel's slopes, have been calculated.

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Double-layer effect on trichloroacetic acid reduction at the dropping mercury electrode. II

Journal of Electroanalytical Chemistry ◽

10.1016/s0022-0728(68)80280-3 ◽

1968 ◽

Vol 16 (1) ◽

pp. 83-87 ◽

Cited By ~ 5

Author(s):

Giancarlo Torsi ◽

Paolo Papoff

Keyword(s):

Double Layer ◽

Trichloroacetic Acid ◽

Mercury Electrode ◽

Dropping Mercury Electrode ◽

Layer Effect ◽

Acid Reduction

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Polarography of n-butylthioglycolate in aqueous media, methanol, and acetonitrile

Canadian Journal of Chemistry ◽

10.1139/v84-310 ◽

1984 ◽

Vol 62 (9) ◽

pp. 1817-1821

Author(s):

K. C. Gupta ◽

Kalpana K. Sharma

Keyword(s):

Aqueous Media ◽

Mercury Electrode ◽

Wave Characteristics ◽

Anodic Wave ◽

Diffusion Controlled ◽

Dropping Mercury Electrode ◽

Drop Time ◽

And Diffusion ◽

Mechanism Of The Reaction

The polarographic behaviour of n-butylthioglycolate (RSH) at the DME in aqueous media, methanol, and acetonitrile has been investigated in the presence of 0.1 M KNO3 and 0.01% thymol. The effect of pH, concentration of RSH, and drop time on the wave characteristics and the mechanism of the reaction occurring at the surface of the mercury drop have been studied. Well-defined reversible and diffusion-controlled anodic waves were obtained in aqueous media (pH 4.2), 40% methanol (pH 3.22), and 40% acetonitrile (pH 2.96). Mathematical and analytical evidence was obtained to show that the anodic wave of RSH at a dropping mercury electrode in aqueous media, 40% methanol, and 40% acetonitrile is due to the formation of the mercury complex RSHg. The dissociation constant (pK) of the mercapto group in n-butylthioglycolate is 9.6 and the diffusion coefficient in the different media are 1.17 × 10−6 cm2 s−1 (in aqueous media) 1.23 × 10−6 cm2 s−1 (in 40% methanol), and 2.43 × 10−6 cm2 s−1 (in 40% acetonitrile). The linearity of id with RSH concentration provides a rapid and precise method for the determination of RSH, down to 0.4 mM in aqueous media, methanol, and acetonitrile.

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The Behaviour of Lead in Iodide Medium at the Dropping Mercury Electrode. I. D.C. Polarographic Study

Australian Journal of Chemistry ◽

10.1071/ch9620729 ◽

1962 ◽

Vol 15 (4) ◽

pp. 729 ◽

Cited By ~ 6

Author(s):

VS Srinivasan ◽

AK Sundaram

Keyword(s):

Mercury Electrode ◽

Polarographic Study ◽

Lead Iodide ◽

Low Concentrations ◽

Dropping Mercury Electrode ◽

High Concentrations ◽

Adsorption Wave ◽

Second Wave

The polarography of lead in the iodide medium has shown that an irreversible wave is obtained at moderate concentrations of lead, whereas at high concentrations two waves are obtained and at low concentrations a single reversible wave is obtained. This explains the irreversible waves obtained by the earlier workers who have mainly worked in the region of 0.4mM of lead. From a study of the effect of the head of mercury, temperature, etc. it is shown that the second wave is an adsorption wave resulting from the adsorption of lead iodide complexes at the dropping mercury electrode.

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Reduction of indium(III) at dropping mercury electrode in the presence of pyridine in aqueous and ethanol–water media

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc2010002 ◽

2010 ◽

Vol 75 (6) ◽

pp. 653-663 ◽

Cited By ~ 1

Author(s):

Vinita Sharma ◽

Krishna D. Gupta

Keyword(s):

Mercury Electrode ◽

Complexation Reaction ◽

Complex Species ◽

Diffusion Controlled ◽

Straight Line ◽

Half Wave ◽

Dropping Mercury Electrode ◽

Water Media ◽

Single Complex ◽

The Stability

The reduction of indium(III) at dropping mercury electrode in aqueous as well as in 25% ethanol–water media in the presence of pyridine has been studied at a constant ionic strength (0.1 M KNO3) and at 30 and 40 °C. The reduction is diffusion-controlled but the electrode process is quasi-reversible in both media. The reversible half-wave potential values,E1/2r, have been obtained by Gelling’s method. The plot ofE1/2r versus pyridine concentration is a straight line and the number of ligands,j, was determined from the slope. This shows the formation of a single complex. The stability constant has been determined by Lingane’s method. In(III) forms one complex species with composition 1:1, [In(py)]3+. The values of thermodynamic parameters ΔG, ΔHand ΔSof the complexation reaction have also been determined at 30 °C.

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Polarography of aromatic azo compounds. II. Kinetic study of the disproportionation of 4-Aminohydrazobenzene-4'-sulphonic acid

Australian Journal of Chemistry ◽

10.1071/ch9650619 ◽

1965 ◽

Vol 18 (5) ◽

pp. 619 ◽

Cited By ~ 20

Author(s):

TM Florence

Keyword(s):

Mercury Electrode ◽

Sulphonic Acid ◽

Azo Compounds ◽

Rate Determining Step ◽

A Value ◽

Controlled Potential Electrolysis ◽

Mercury Cathode ◽

Dropping Mercury Electrode ◽

Controlled Potential ◽

Aromatic Azo Compounds

Solutions of 4-aminoazobenzene-4'-sulphonic acid were reduced by controlled potential electrolysis at a mercury cathode, and the disproportionation rate of the hydrazo derivative determined by spectrophotometry and polarography. The kinetics of the reaction were found to be first-order with respect to both hydrazo and hydrogen ion concentrations, although the overall reaction involved two molecules of the hydrazo compound. In the rate law, -d[hydrazo]/dt = k[H+][hydrazo], k was calculated to be (5.0�0.3) x 106 l. mole-1 sec-1 from spectrophotometric measurements, and (4.5�0.5) x 106 l. mole-1 sec-1 by polarography (25�). A reaction mechanism based on a rate determining step involving a quinonediimine intermediate has been proposed. Another value of the disproportionation rate constant was obtained from the effect of drop time on the limiting currents of 4-aminoazobenzene-4'-sulphonic acid at the dropping mercury electrode. A value of k of (22�5) x 106 l. mole-1 sec-1 was determined by this method. Reasons for the discrepancy between this result, and those found by direct measurement, are discussed.

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