Controlled-potential Coulometric Method Research Articles

Narrow span coulometric analysis of neptunium

A narrow span (E o ′ ±0.1 V) controlled potential coulometric method has been developed for the determination of neptunium in 1M H2SO4 with a RSD of 0.2%. The main advantage of this method over the existing coulometric methods is that it can tolerate up to a 5-fold excess of plutonium. The method involves carrying out the electrolysis to about 97% and calculating by an iterative computation the formal electrode potential in situ, which is used to calculate the total amount present in the sample. The method consists in oxidation of all the neptunium to Np (VI) by Ce(IV), destruction of excess Ce(IV) and reduction of Np(VI) to Np(V) by NaNO2, destruction of excess nitrite by sulfamic acid followed by coulometric titration of Np(V) to Np(VI).

Coulometric microdetermination of nitrite via diazotization of 1-amino-4-naphthalenesulfonic acid

A controlled-potential coulometric method for the trace determination of nitrite is described. It is based on the formation of a diazonium salt with 1-amino-4-naphthalenesulfonic acid in a Britton-Robinson buffer (pH 1.5). The method is characterized by a high degree of accuracy and by an experimental detection limit of 0.1 ppm (2.17 × 10 −6 M) of nitrite.

Controlled-potential coulometric determination of plutonium with a hydrochloric acid—sulfamic acid electrolyte and phosphate complexing

Total plutonium is selectively determined by a controlled-potential coulometric method in which plutonium is reduced to Pu(III) at 0.25 V (vs. SCE) in a 5.5 M hydrochloric acid—0.015 M sulfamic acid electrolyte, diverse ions are oxidized at 0.57 V, phosphate is added to reduce the Pu(III)—Pu(IV) potential, and Pu(III) is oxidized to Pu(IV) at 0.68 V. None of more than 50 metal ions present in nuclear fuel-cycle material interferes. Many anions are without effect and most interfering ones are removed by preliminary fuming with perchloric acid. The apparatus described consists mainly of commercial components. The relative standard deviation is <0.1% at the 5-mg plutonium level.

Controlled-potential coulometric determination of platinum in americium—platinum alloys

A controlled-potential coulometric method for the determination of platinum in americium—platinum alloys is described. Platinum in the hexachloroplatinate complex is reduced to the metal at —0.3 V vs. the saturated silver chloride electrode on a mercury pool electrode. For quantities up to 5 mg, the standard deviation was 6.4 μg.

A test for the reliability of the controlled potential coulometric method to determine plutonium in uranium-plutonium mixtures

The purpose of the present paper is to give the results obtained when testing the controlled potential coulometric method applied to the measurement of plutonium in an uranium/plutonium mixture. Successive oxidation and reduction values connected to different values of the cut-off current are compared for plutonium and uranium/plutonium. The origin of the positive discrepancy obtained in the case of uranium/plutonium is explained and the appropriate working conditions to obtain reliable plutonium measurements in a mixture with uranium are indicated.

Controlled-potential iodometric titration of nitrite. Application to the determination of nitrite in meat products

A controlled-potential coulometric method using iodine as an intermediate has been devised for the determination of nitrite. Nitrite is reduced by iodide and the iodine formed is then reduced coulometrically. The reduction of nitrite in the pH range 0–6 has been studied and the optimum conditions for an accurate determination are stated. The time of analysis for a determination in the range 0·005–5 mg of nitrite is about 2–5 min and the error ± 0·1%. The method is applied to the determination of nitrite in some meat products.

Coulometric determination of dissolved oxygen in water

The oxygen content of air-saturated distilled water has been determined at between 10 and 40° by using a controlled-potential coulometric method based on an earlier published method for the iodometric determination of nitrite. The maximum error for the determinations was ± 0.3% over the whole range, and the time of analysis about 3 min. An equation is given for the solubility in the measured range, and some thermodynamic functions are calculated.

The Chemical Characterization of Uranium Nitrides

Chemical analysis techniques were demonstrated for three uranium nitride specimens. Sintered uranium mononitride (UN), unsintered UN powder, and UN1.572 powder were analyzed for the major constituents, and a mass balance of 100.00 ± 0.03% was realized in every case. The gravimetric determination of uranium in these materials by an oxidation-reduction-oxidation method gave good precision and accuracy. Results from the direct oxidation method were strongly dependent on the oxygen content of the gas used to oxidize the sample. The controlled-potential coulometric method was used to confirm the gravimetric uranium results. The Dumas method for nitrogen determinations was shown to be superior to the Kjeldahl for both UN and UN1.572. Inert gas fusion is suitable for the determination of oxygen and a conventional combustion method is suitable for carbon determinations. Sintered UN provided a mass balance of 99.989% with a mole ratio N+O + C/U = 0.997 and a crystal lattice parameter a = 4.8896 ± 0.0001 Å. The microstructure of this sample consisted of single phase mononitride.

The determination of plutonium in refractory materials by electrometric methods after dissolution by fusion with ammonium hydrogen sulphate

A fusion with ammonium hydrogen sulphate at 400° C has been developed for the dissolution of refractory materials containing plutonium dioxide. On cooling, each melt is leached with sulphuric acid to produce a solution suitable for analysis for plutonium by electrometric methods. Plutonium concentrations (about 2 mg per ml) are determined either by a potentiometric titration based on the reduction of plutonium(VI) to plutonium(IV), or by a controlled-potential coulometric method, the Pu3+-Pu4+ couple being used. Both techniques are suitable for the accurate determination of plutonium with a precision of better than 0·20 per cent. (coefficient of variation) for about 5-mg amounts or less. The behaviour of many other elements in these methods has been studied in some detail.The fusion technique has been found to be suitable for the dissolution of several refractory materials, including samples of PuO2-UO2 fired at 1550° C, and also samples of PuO2-ThO2 produced by the ignition at 900° C of the carbides of these elements coated with pyrolytic graphite. The determination of the plutonium contents of these samples was then completed directly by the electrometric methods.

Nickel(IV) dimethylglyoxime

The red solutions of nickel dimethylglyoxmie in strongly basic solution have been studied by electrochemical, spectrophotometric and magnetic methods. It is concluded that the red complex is a species of Ni(IV). A controlled potential coulometric method for the analysis of nickel is also presented.

Polarographic and Coulometric Studies of cis-Dioxalatodiaquochromate(III)

Abstract The current-voltage curves of cis-dioxalatodiaquochromate (III) have been recorded at the dropping mercury electrode in various supporting electrolyte solutions. A well-defined wave with a half-wave potential of −1.522 V. vs. SCE was obtained in 0.3 m potassium chloride solutions containing 0.005% gelatin. The limiting current in this case was proved to be diffusion-controlled from its dependence on the effective pressure of mercury on the dropping mercury electrode and from the characteristics of the current-time curve during the life of a mercury drop. The electrode reaction of the complex was found to be irreversible by a study of both the characteristics of the Kalousek polarogram and the relation of log{\bari⁄\barid–\bari)} against E. The number of electrons involved in the reduction was determined by the controlled-potential coulometric method. The coulometric investigation showed that cis-dioxaloto-diaquochromate(III) is reduced to the metal at the dropping mercury electrode. This conclusion was also supported by the detection of chromium from the surface of the mercury pool electrode used in the controlled potential electrolysis. The value of the diffusion coefficien t of cis-dioxalatodiaquochromate (III), calculated for a three-electron reduction, was also reasonable in comparison with those of other chromium (III) complexes.

Determination of Technetium by Controlled-Potential Coulometric Titration in Buffered Sodium Tripolyphosphate Medium.

A controlled-potential coulometric method for the determination of Tc was developed whereby Tc(VII) is titrated in an acetate-buffered (pH 4.7) solution of sodium tripolyphosphate at a potential of --0.70 volt vs S.C.E. In the range from about 0.5 to 5 mg of Tc(VII) titrated, the relative error of the method is about 450 deg C in a 1% and the relative standard deviation about 0.5%. Various possible interferences were studied; Tc(VII) can be removed quantitatively from most interfering ions by distillation from sulfuric acid solution. The method is relatively simple and rapid. (auth)

Coulometric Determination of Uranium(IV) by Oxidation at Controlled Potentials

A controlled-potential coulometric method is described for the titration of uranium(IV). At potentials more positive than plus or minus 0.5 volt vs. the Ag/AgCl electrode, uranium(IV) is oxidized at a platinum electrode. The oxidation is sufficiently rapid and complete at a potential of +1.4 volts for use in the titration of uranium, although the uranium(IV/ VI) couple is not reversible. The method has been applied to the determination of uranium(IV) in samples of UO/sub 2/ and in ThO/sub 2/- UO/sub x/ mixtures dissolved in H/sub 3/ PO/sub 4/. From 1 to 10 mg of uranium(IV) in 1 M solutions of H/sub 3/PO/sub 4/, H/sub 2/SO/sub 4/, HClO/sub 4/, or HNO/sub 3/ can be determined by this method with a coefficient of variation of 0.3%. (auth)

Extraction, Controlled-Potential Coulometric Method Specific for Uranium(IV)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExtraction, Controlled-Potential Coulometric Method Specific for Uranium(IV)G. L. Booman and W. B. HolbrookCite this: Anal. Chem. 1959, 31, 1, 10–16Publication Date (Print):January 1, 1959Publication History Published online1 May 2002Published inissue 1 January 1959https://doi.org/10.1021/ac60145a003RIGHTS & PERMISSIONSArticle Views84Altmetric-Citations37LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Polarographic and Coulometric Studies of Tropolone

Abstract The current-voltage curves of tropolone were recorded at the dropping mercury electrode in buffer solutions of various pH’s containing no borate. One reduction wave was observed in the pH region of 2.2 to 4.0, two waves with nearly equal heights, in the pH region of 5 to 6 and one wave, in the solution of pH higher than 8. All waves except the second in the intermediate pH region were found to shift to negative potentials with the increase of pH of the solution by approximately 70 mV./pH. The number of electrons involved in the reduction was determined by the controlled potential coulometric method. One-electron reduction was confirmed for the first wave at lower pH’s, two-electron reduction for the two-step waves at the intermediate pH region and two-electron reduction for the wave at higher pH’s. The current-voltage curves which were recorded with the solution preliminarily subjected to the controlled potential electrolysis gave two new waves; one is anodic and the other, cathodic. The former decreased with time and the latter increased. This indicates that the reduction product of tropolone is unstable and changed gradually to the substance which gives the reduction wave. The diffusion coefficients of tropolone were calculated from the limiting current using the revised Ilkovic equation.