John T. Stock

The cathodic stripping voltammetry of certain thiols in acetate medium

Abstract The cathodic stripping voltammetry of six thiols by deposition at a hanging mercury drop electrode (+0.05 V vs. SCE) from acetate-buffered solution (pH 4.76) and scanning to —0.8 V is described. Peak potentials are reported. The peak height—concentration relationships are reasonably linear in the range 0.4–1.2 μM. The compounds tested are 2-mercaptopyridine, 2-mercapto-3-pyridinol, 2-mercaptopyridine- N -oxide, mercaptosuccinic acid, 2-mercaptopyrimidine and cysteine hydrochloride.

The palladium electrode in aqueous and nonaqueous titrimetry

Abstract Two modifications of the palladium-hydrogen electrode of Schwing and Rogers have been made and tested. A new form of “generation” electrode with a vertical palladium diaphragm and fast constant speed circulation has been devised. This form of electrode responds rapidly and has been used in a variety of acid-base titrations in aqueous and nonaqueous systems.

Redox titrations at millimolar concentration in n,n-dimethylformamide media

Abstract Potentiometric oxidation-reduction titrations in N,N-dimethylformamide (DMF) have been shown to be valid at millimolar concentrations of titrand. Forward and reverse titrations that involve the oxidants copper(II), chromium(VI), iron(III), and mercury(II) with the reductants titanium(III), cobalt(II), ascorbic acid, cysteine, and thiolactic acid have been examined. Some preliminary results of titanium(III) in DMF titrimetry in the determination of copper and iron in alloys are presented.

Biamperometric titration of hexacyanoferrate(III), iron(III), copper(II), cerium(IV), and iodine with mercury(I) perchlorate

Abstract The biamperometric titration of hexacyanoferrate(III), iron(III), copper(II), cerium(IV), and iodine with mercury(I) perchlorate has been studied. In the concentration range 50 to 1000 μ N , the error rarely exceeds 2 %. Although the biamperometric and R.P.E. amperometric techniques are of comparable utility at concentrations down to 100 μ N , the amperometric technique is preferable for low-concentration titrations.

Dissimilar-metal and “titrant-stream” electrode systems in the potentiometric titration of millimolar concentrations of copper(II) in dimethylformamide with titanium(III)

Abstract Thirty platinum-nonplatinum electrode couples have been examined as possible end point indicators in the potentiometric titration of millimolar concentrations of copper(II) in N.N -dimethylformamide with titanium(III) in the same solvent. Molybdenum, titanium, or stainless steel gave standard deviations of less than 1%. If preconditioned, gold, tantalum, or tungsten gave similar standard deviations. Several other platinum-nonplatinum electrode couples are useful but less satisfactory. Titrations carried out with the platinum (titrant stream)-platinum (titrand) couple gave a standard deviation of less than 2%. The stainless steel (titrant stream)-stainless steel (titrand) couple is also useful but is somewhat less precise.

The analysis of bromide-chloride mixtures by amperometric titration: Application to halogen determination in organic compounds

Abstract The analysis of milligram quantities of a mixture of bromide and chloride can be carried out by the argentometric amperometric titration of two aliquots of the solution. Total halide is determined in one aliquot, while the second aliquot is titrated after the elimination of bromide by bromate oxidation. The procedure has been extended to permit the analysis of organic halogen compounds.

Flue gas monitoring: an early application of mechanized analysis

Abstract Mechanized chemical analysis is by no means new. The monitoring of the CO2 content of flue gases opened the way to more efficient boiler operation and replacement of the tedious manual procedure for this by mechanized devices began around the turn of the present century.

Karl Fischer titrimetry with bimetallic potentiometric electrode systems

Abstract Seven bimetallic electrode couples in which one member was platinum have been examined as indicators in the Karl Fischer titration of water in methanol and in methanolic solvent mixtures. The platinum-gold potentiometric couple requires no polarizing source, and gives results that compare favorably with those obtained at the biamperometric platinum-platinum couple.

Sources of error in the mercury(I) titration of low concentrations of hexacyanoferrate(III) in alkaline iodide medium

Abstract Although submillimolar concentrations of hexacyanoferrate(III) in acid thiocyanate medium can be accurately titrated amperometrically with mercury(I) perchlorate, the titration is unsatisfactory when carried out in alkaline iodide medium. The decay of hexacyanoferrate(III) current in alkaline iodide medium and the effect of cyanide ion on the titration have been examined. The results provide an explanation for positive and negative titration errors that are encountered when hexacyanoferrate(III) is titrated in this medium.

Electrode deactivation in the anodic voltammetry of some phenolic derivatives of isoquinoline

Abstract The anodic voltammetry of submillimolar concentrations of 7-hydroxy-1,2,3,4-tetrahydroisoquinoline, and of the related compounds corypalline and coclaurine, has been examined at the rotating platinum microelectrode (RPE) and at the drum-activated platinum electrode (DAPE) of Berge and Strubing. The electrolysis of these compounds markedly deactivates the RPE, but has a much smaller effect upon the performance of the DAPE.