Rotating Platinum Electrode Research Articles

Electrode reactions of tris(2,2′-bipyridine)-iron(II) and tris(2,2′-bipyridine)iron(III) complexes in acetonitrile solution

The electrode processes of tris(2,2′-bipyridine)iron(II) and tris(2,2′-bipyridine)iron(III) complexes at the rotated platinum electrode and the dropping mercury electrode (dme) in acetonitrile solutions have been investigated by the measurement of current/potential curves, dc and ac polarograms and Kalousek polarograms. The system of the iron(II) and the iron(III) complex was reversible at the rotated platinum electrode. The iron(II) complex gave a five-step reduction wave at the dme when tetraethylammonium perchlorate was used as supporting electrolyte. The limiting currents of the first three steps named from positive to negative potentials were all diffusion-controlled and of a one-electron reduction processes. From the effect of free 2,2′-bipyridine and water on the reduction wave of the iron(II) complex and from the shape of Kalousek polarograms, the electrode processes for the first three steps are concluded to be the reductions from [Fe(bipy)3]2+, [Fe(bipy)3]+ and [Fe(bipy) 3], respectively. It has been proposed that at the third step univalent tris(2,2′-bipyridine)-ferrate anions, [Fe(bipy)3]−, are formed at the electrode surface in acetonitrile.

The voltammetry of ethylenediaminetetraacetic acid (EDTA) and related compounds on a rotating platinum electrode

The behaviour of EDTA, ethylenediamine, iminodiacetic, 1,2-diaminocyclohexanetetraacetic, nitrilotriacetic, ethyleneglycol-bis-(2-aminoethylether)tetraacetic, diethylenetriaminepentaacetic, and triethylenetetraminehexaacetic acids was studied on a rotating platinum electrode. These substances, with the exception of ethylenediamine and iminodiacetic acid, yield anodic voltammetric waves on a platinum electrode, the heights and half-wave potentials of which are dependent upon pH and the composition of the solution. The probable mechanism of the electrode reactions is given.

The voltammetry of ethylenediaminetetraacetic acid (EDTA) and related compounds on a rotating platinum electrode

The behaviour of EDTA, ethylenediamine, iminodiacetic, 1,2-diaminocyclohexanetetraacetic, nitrilotriacetic, ethyleneglycol-bis-(2-aminoethylether)tetraacetic, diethylenetriaminepentaacetic, and triethylenetetraminehexaacetic acids was studied on a rotating platinum electrode. These substances, with the exception of ethylenediamine and iminodiacetic acid, yield anodic voltammetric waves on a platinum electrode, the heights and half-wave potentials of which are dependent upon pH and the composition of the solution. The probable mechanism of the electrode reactions is given.

Electrolytic Oxidation of Aromatic Amines

The electrolytic oxidation of anilines at a rotating platinum electrode in acetonitrile in the presence of pyridine involved a two electron change and formed azobenzenes. Evidence for the mechanism was the voltammetric behavior of hydrazobenzenes, p‐phenylenediamine and 4,4'‐dimethoxyazobenzene and the formation of azobenzenes in macroscale oxidations. The behavior of anilines in the absence of pyridine was more complex since the amine acted as a base and formed a salt which was not easily oxidized. Exceptions were the weakly basic o‐nitroaniline, p‐nitroaniline, 2,4‐dinitroaniline and the reversible systems, o‐phenylenediamine and p‐phenylenediamine; two electrons were involved for these examples.

Electrochemical oxidation of some aromatic amines in acetonitrile medium: II. Benzidine, N,N,N′,N′-tetramethylbenzidine, and 1,4-phenylenediamine derivatives

The polarographic behavior of benzidine, N,N,N′,N′-tetramethylbenzidine, 1,4-phenylenediamine, N,N,N′,N′-tetramethyl-1,4-phenylenediamine, N,N′-diphenyl-1,4-phenylenediamine, N,N′ — bis — 4 — dimethylaminophenyl — 1,4 — phenylenediamine, 4 — dimethylamino- N-methyldiphenylamine, 4-dimethylaminodiphenylamine and 4-aminodiphenylamine has been studied in acetonitrile medium on the rotating platinum electrode and the possibility has been shown of utilizing the oxidation wave of these substances for their polarographic determination, taking into account the influence of water in the solvent and the acidity of the medium. Coulometric generation at constant current has been used to investigate the number of electrons exchanged in the reaction. The products formed in the electrode reaction are discussed.

Electrochemical oxidation of some aromatic amines in acetonitrile medium: III. 4,4′-Diaminodiphenylamine, its N-methyl derivatives, and tris-(4-dimethylaminophenyl)amine

The polarographic behavior of 4,4′-diaminodiphenylamine and of its methylated derivatives [4,4′-bis(dimethylamino)- N-methyldiphenylamine; 4,4′-bis(dimethylamino) diphenylamine; 4-dimethylamino-4′-aminodiphenylamine; 4,4′-(diaminodiphenylamine)] and of tris(4-dimethylaminophenyl)amine has been studied in acetonitrile medium on the rotating platinum electrode, and the possibility has been shown of utilizing the oxidation waves of these substances for their polarographic determination, taking into account the influence of water contained in the solvent and acidity of the medium. Constant current coulometric generation has been used to study the number of electrons exchanged in the reaction. The discussion summarizes the conclusions following from Parts I–III of this series and the relations between the polarographic behavior and structure of the reacting substances are discussed.

Continuous and Quantitative Polarographic Analysis of Dithionites

Amperometric titration, using either a dropping‐mercury electrode or a rotating platinum electrode as the indicator electrode and Rubine as the titrant, has been shown to be a useful method of analysis of sodium and zinc dithionites. From controlled potential electrolysis, it was confirmed that the anodic oxidation of dithionite involves two electrons per dithionite ion, sulphite being identified polarographically as one of the products of the reaction. A continuous voltammetric determination of dithionite is described that could possibly be adapted for the control of industrial processes in which dithionite is used.

Electrochemical oxidation of some aromatic amines in acetonitrile medium. I. N,N-dimethylaniline, triphenylamine, diphenylamine and di-4-tolylamine

The polarographic behavior of N,N-dimethylaniline, triphenylamine, diphenylamine, and di-4-tolylamine has been studied in acetonitrile medium on a rotating platinum electrode. It has been found possible to apply the oxidation waves of these substances to their polarographic determination, considering the water content of the solvent, temperature and acidity of the medium. Constant current coulometric generation has been used to study the number of electrons exchanged in the reactions. The products formed in the electrode reaction are discussed.

The amperometric titration of submillinormal concentrations of hexacyanoferrate (III) with mercury (I) perchlorate

Although quite precise under rigidly controlled conditions, the mercury(I) amperometric titration, at a rotating platinum electrode, of submillinormal concentrations of hexacyanoferrate(III) in sodium hydroxide-potassium iodide medium gives results that vary with the concentrations of alkali, iodide and hexacyanoferrate(III). Dependence upon solution composition is small in perchloric acid-potassium thiocyanate medium. In this medium, the titration of 5 × 10–5 to 10–3N hexacyanoferrate(III) is precise and accurate to within ±1·5 per cent. The titration of 5 × 10–6N hexacyanoferrate(III) is precise to about 5 per cent.

Proprietes chimiques en solution dans le bromure d'ethylpyridinium fondu: II. Formation de complexes du titane(III) et du titane(IV) avec des molecules organiques azotees

Electrochemical and chemical properties of titanum in fused ethylpyridinium. bromide, at 127°, have been studied. The sole redox system for this element is Ti 4+/Ti 3+, ethylpyridinium cation being reduced before Ti 3+. The standard potential of the system, versus the normal hydrogen electrode in this medium, is −0.205 V (+0.120 V for the I 2/I − system, and +0.460 V for the Br 2/Br − system). By determination of current-potential curves with a rotating platinum electrode. I:I complexes have been identified between Ti 3+ and pyridine, 2,2'-dipyridyl, 1,10-phenanthroline and PAN. and also between Ti 4+ and the same compounds except, pyridine. The titanous complexes are more stable than the titanic complexes.

Voltammetric behavior of some selected metal ions in propionic, isobutyric and acrylic acids

The polarographic behavior of copper(II), copper(I), cadmium, lead(II), and thallium (I) ions and the voltammetric behavior of silver ion at the rotating platinum electrode in 1.0 M lithium perchlorate solutions of anhydrous propionic acid, isobutyric acid, and acrylic acid have been examined and compared with those in anhydrous acetic acid.

Proprietes chimiques en solution dans le bromure d'ethylpyridinium fondu: III. Formation de complexes oxyde du titane(IV); echance de O 2− avec d'autres oxydes metalliques

The formation of the oxo-complex TiO 2+, followed by precipitation of the insoluble dioxide TiO 2, was studied electrochemically with the aid of a rotating platinum electrode. The reactions were realized by addition, to a TiCl 4 solution in fused ethylpyridinium bromide, of H 2O or Li 2CO 3, which act as O 2- anion donors. The equilibrium constant is k 1 = 0.4 kg mole −1 for 2 TiO 2+ TiO 2↓ + Ti 4+. Amperometric measurement of the concentrations of Ti 4+ and TiO 2+ cations in this medium, enabled the equilibria of O 2− exchange between Ti 4+ and Zr 4+, and between TiO 2+ and Al 3+ to be determined, giving a classification of oxo-complex stabilities as : TiO 2+ > ZrO 2+ > AlO + (dissociation-pK differences are: TiO 2+—ZrO 2+, 2.25; TiO 2+—AlO +, 2.5).

Automation of amperometric titrations with rotating platinum electrodes

A modification of an earlier described apparatus allows for the automation of amperometric titrations with rotating platinum electrodes.

Voltammetry in ammonium fluoride solution with particular reference to manganese

The voltammetric behaviour of 19 ions in 1M ammonium fluoride solution has been investigated, using a rotating platinum electrode. In this base electrolyte, manganese(II) is oxidised reversibly to manganese(IV) at + 0.52 V vs. S.C.E. and this reaction has formed the basis for a simple voltammetric method for the determination of steels and cast iron of low cobalt content.

Study of the properties of lead tetraacetate as oxidizing and oxidimetric reagent in analytical chemistry: II. Polarographic behavior of tetravalent lead

A polarographic investigation of the behavior of tetravalent lead on a rotating platinum electrode has shown that in a medium of perchloric and hydrochloric acid polarographic waves may be obtained, corresponding to the reduction of tetravalent to bivalent lead, with limiting currents proportional to the lead concentration in the range of 1 · 10 −4 to 1 · 10 −3 M Pb(IV). A more detailed study of the reaction of tetravalent lead on the platinum electrode in HCl medium has shown that tetravalent lead may be distinguished and determined polarographically in solution even in the presence of chlorine, which is reduced at potentials more positive than the potential of the tetravalent lead wave.

Polarography of arylpropynyl ether derivatives. I. Polarography of 2,4-dichlorophenyl 3-iodo-2-propynyl ether and 2,4,5-trichlorophenyl 3-iodo-2-Propynyl ether

The polarographic nature of 2, 4-dichlorophenyl 3-iodo-2-propynyl ether (DCPI) and 2, 4, 5-trichlorophenyl 3-iodo-2-propynyl ether (TCPI), used as good anti-trychophyton agents, was examined. Three reduction waves were observed in DCPI and two in TCPI. First and second waves of DCPI and first wave of TCPI were small, there was no transition of the half-wave potentials by pH, and the wave height did not make proportional increase with the concentration. From contact with metallic mercury, electrocapillary curves, and from polarography with rotated platinum electrode, the first wave in both compounds was considered to be the adsorption wave. The 3rd wave of DCPI and 2nd wave of TCPI showed linear increase proportional with the concentration, and they were found to be the reduction wave due to deiodination from the fact that the reduction products by electrolysis at controlled potential were 2, 4-dichlorophenyl 2-propynyl ether from DCPI and 2, 4, 5-trichlorophenyl 2-propynyl ether from TCPI.

The kinetics of bromination of hydrazones

Kinetic measurements on the rate of bromination of a series of arylidene arylhydrazines have been made in 70% aqueous acetic acid at 20°, by following the diffusion current of bromine (initially ca. 10–5M) at a rotating platinum electrode. Substituents in the benzylidene ring have a smaller effect (ρ=–0·62) than those in the other ring (ρ=–2·2). This has been rationalised in terms of an intermediate stabilised by considerable charge delocalisation.

Polarographic Behavior of Mercuric Ion at a Rotating Platinum Electrode

Polarographic Behavior of Mercuric Ion at a Rotating Platinum Electrode

The amperometric titration of submillinormal concentrations of copper(II) with mercury(I) perchlorate

Although quite precise under rigidly controlled conditions, the mercury(I) amperometric titration, at a rotating platinum electrode, of submillinormal concentrations of copper(II) in potassium thiocyanate-perchloric acid medium gives results that vary with the concentrations of thiocyanate and of copper(II). When this variation is eliminated by the addition of potassium iodide, the titration of 10–5N to 10–4N copper(II) is precise and accurate to within ±1·5 per cent. The titration of 10–6N copper(II) is precise to about 5 per cent.

The Oxidation-Reduction Potential of the System of Mn(II)EDTA-Mn(III)EDTA Complexes and the Stability Constant of Mn(III)EDTA Complex

Abstract The standard oxidation-reduction potential of the system of Mn(II)EDTA-Mn(III)EDTA complexes has been determined to be E°MnY=0.579V. vs. SCE from the potentiometric measurement with the rotated platinum electrode. From this value the logarithmic stability constant of the Mn(III)EDTA complex (logKMn(III)Y) has been calculated to be 24.9 at 25.0°C and μ=0.2.