The Coulometric Titration of Chromate and of Vanadate by Means of Electrolytically Generated Cuprous Copper and an Amperometric End-Point

Meier, D. J.; Myers, Rollie J.; Swift, Ernest H.

doi:10.1021/ja01175a024

Cited by 73 publications

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“…The apparatus in its present form is not convenient for the titration of samples containing from 200 to 600 micrograms, or more than 2000 micrograms, because of the excessive time required (greater than 300 seconds). Provision has been made for an intermediate rate of generation in an improved apparatus (5).…”

Section: Methodsmentioning

confidence: 99%

“…By maintaining a constant rate of bromine generation and measuring the time of generation, the number of equivalents of bromine generated can be determined. The advantages of such secondary coulometric processes in w'hich an intermediate reactant-in this case bromide-is provided in relatively large concentration, so that both constancy and efficiency of current generation can be maintained throughout the titration, have been discussed by Meier, Myers, and Swdft (5). Inasmuch as the coulometric principle possesses certain unique advantages, especially its adaptability to automatic titration procedures, further investigations of its applicability seemed desirable.…”

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confidence: 99%

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Coulometric Titration of Iodide

Wooster¹,

Farrington²,

Swift³

1949

Anal. Chem.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Coulometric Titration of Iodide

Wooster¹,

Farrington²,

Swift³

1949

Anal. Chem.

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“…The full significance of this is not indicated by the data presented, for the sample itself contained few of the heavier saturated, unsaturated, and ring hydrocarbons that are ordinarily present in fuel gases of this type, and the spectrometer is capable of analyzing a mixture of 20 or more components that would prove a vexing and rather durable problem to one employing conventional chemical methods. As in the analysis of a natural gas (2), oxygen was correctly determined in the present sample by the spectrometer and not by the volumetric chemical method. However, the spectrometric method needs considerable improvement in the determination of hydrogen and particularly carbon monoxide.…”

Section: Reviewmentioning

confidence: 92%

“…For the titration of reducing agents, bromine has been employed rather extensively (1, 3, 5, 7, S) and recently Ramsey, Farrington, and Swift (4) have shown that iodine can be used for the titration of arsenic. Cuprous copper has been used for the coulometric titration of certain oxidizing agents (2).…”

Section: Literature Citedmentioning

confidence: 99%

Coulometric Titrations with Chlorine Titration of Arsenic and Use of Amperometric End Point

Farrington¹,

Swift²

1950

Anal. Chem.

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“…The deposits were found to contain chromium, zinc, and potassium. Chromium was determined by a coulometric titration with electrogenerated Cu(I) using a biamperometric endpoint as described by Meier, Myers, and Swift (12).…”

Section: Reagents and Solvent Preparation--anhydrousmentioning

confidence: 99%

Electrochemistry of Potassium Chromate in Molten Zinc Chloride‐Potassium Chloride Eutectic

Deanhardt¹,

Hanck²

1975

J. Electrochem. Soc.

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The electrochemistry of K2CrO4 in an equimolar ZnC12-KC1 eutectic at 300~ was investigated by chronopotentiometric, chronoamperometric, and neovoltammetric techniques. The reduction occurs as a single, irreversible, diffusion-control.led step yielding an insoluble electrode deposit that would not undergo electrochemical oxidation. The value of nDox 1/2 at 300~ was found to be (3.46 • 0.10) • 10-~ eq-cm/mole-sec ~/~. The charge transfer step was found to be totally irreversible; a = 0.57 and kh.f (at 1.2V) ----4.46 • 10 -4 cm/sec. Chemical analyses were performed to determine the composition of the electrode deposit. The deposit appears to be an unstoichiometric compound of the general form KzZn~CrOz where x, y, and z depend upon the conditions of the electrolysis. A mechanism consistent with the observed results is proposed.The electroreduction of chromate has been the subject of extensive investigation by Laitinen and coworkers because of its use as a depolarizer in thermal batteries (1-5). Their studies were carried out in LiC1-KC1, a neutral, nonoxidizing solvent. With the addition of acidic ZnC12 to the LiC1-KC1 solvent, the reduction of chromate is shifted to more positive potentials (4). A mechanism involving the formation of a Zn(II)-Cr(IV) adduct as a reaction intermediate was proposed to account for the positive shift in potential.Recently acidic solvents such as the chloroaluminate melts have gained popularity as solvents for electrochemical studies (6-8). Low oxidation states of metals are usually more basic than the higher oxidation states and are stabilized through formation of an acid-base adduct with strongly acidic solvents. Several such states have been observed in chloroaluminates.In attempting to further characterize the Cr(IV) species proposed by Hanck and Laitinen we sought a solvent acidic enough to stabilize Cr(IV) yet not so acidic as to introduce complications from Cr2072-. Consequently we have elected ZnC12-KC1 as a solvent over the more acidic chloroaluminate melts. The reduction of chromate in LiCI-KC1 containing ZnCI2 is free of side reactions and yields a stoichiometric reduction product, LiZn2CrO4, over a wide range of preparative conditions (4); the influence of A1Cls on the reduction of chromate in LiCI-KC1, on the other hand, has not been fully explored. Experimental Reagents and solvent preparation.--AnhydrousK2CrO4 was obtained by drying reagent grade KeCrO4 (J. T, Baker) at ll0~ for 1 hr and storing over Mg(C104)2 a few days before use.The ZnC12-KC1 eutectic was prepared by vacuum drying reagent grade ZnC12 (J. T. Baker) and reagent grade KCI at 150~ for 48 hr. The two dried salts were mixed in a 1:1 mole ratio under a nitrogen atmosphere and stored over Mg(C104)2 in a vacuum desiccator. To prevent hydrolytic decomposition of ZnCl2, anhydrous HC1 (Air Products electronic grade) was slowly passed through the salt mixture for 30 min during which the temperature was raised from room temperature to 450~ fusion occurred at 230~ The temperature was maintained at 450~ for 1 hr in ord...

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The Coulometric Titration of Chromate and of Vanadate by Means of Electrolytically Generated Cuprous Copper and an Amperometric End-Point

Cited by 73 publications

References 0 publications

Coulometric Titration of Iodide

Coulometric Titration of Iodide

Coulometric Titrations with Chlorine Titration of Arsenic and Use of Amperometric End Point

Electrochemistry of Potassium Chromate in Molten Zinc Chloride‐Potassium Chloride Eutectic

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