Quinhydrone Electrode Research Articles

Potentiometric detectors for the determination of acidity by discontinuous flow analysis

Three potentiometric detectors, each incorporating a vibrating reed mixer, were investigated for use in the determination of acidity by discontinuous flow analysis (DFA). Two of these used PVC and glass membrane pH-sensors, and the third employed a novel differential titration technique based on two quinhydrone electrodes. These detectors were applied to the determination of the total acidity of vinegars and the titratable acidity of wines, the results agreeing well with standard procedures. The analysis of wine proved to be difficult because of the gradual change in pH at the end-point and so a method was developed which determined the titratable acidity at pH 8.3.

Einar Biilmann (1873-1946): pH determination made easy

The quinhydrone electrode system for measuring pH was devised by the Danish chemist Einar Christian Saxtorph Biilmann in 1920.

Standard pH values for potassium hydrogenphthalate reference buffer solutions in acetonitrile—water mixtures up to 70 wt% at various temperatures

Reference value standards, pHs, for 0.05 mol kg −1 potassium hydrogenphthalate (KHPh) reference buffer solutions in 30, 50 and 70 wt% acetonitrile—water mixed solvents at temperatures from 288.15 to 308.15 K have been determined from emf measurements of the reversible cell Pt|Ag|AgCl|KHPh + KCl|Quinhydrone|Pt, in which the H +-reversible quinhydrone electrode replaces the ill-behaving hydrogen electrode. Values of the first ionization constant of the o-phthalic acid (H 2Ph; benzene-1,2 dicarboxylic acid) in these mixed solvents have also been determined from analogous measurements. The consistency of the present results with the previously determined pHs values in 5, 15 and 30 wt% acetonitrile—water mixtures is analysed by multilinear regression of pHs as a function of both solution composition and temperature. These smoothed standard pHs values are used to optimize the parameters of an equation predicting pHs values in different aqueous organic solvents.

Semimicro pH electrodes based on quinhydrone and related systems

AbstractA number of pH measurement systems based on quinhydrone and related compounds have been investigated for their possible use in studies of localized conditions occurring in crevices, stress corrosion cracks, and similar situations. These systems offer the advantage of using a robust electrode of a noble metal as the pH sensitive electrode, which can be made very small. However, they do require a source of the quinhydrone in solution, and this may limit their applicability. Quinhydrone is also limited to neutral and acid solutions, which proved to be a problem in the specific case of crevice chemistry of steels in sea water. Attempts to improve the performance in alkaline solutions by additions to the quinhydrone ring were partially successful, although the compound thus formed was significantly less soluble than quinhydrone, and this gave rise to difficulties in the development of stable potentials. Practical application of the quinhydrone electrode has focused on a semimicro electrode, which can b...

Temperature dependence of the ionisation constants and evaluation of the related thermodynamic parameters for salicyclic acid and meta-hydroxybenzoic acid

The thermodynamic ionisation constants of salicyclic acid and meta-hydroxybenzoic acid for the solvent pure water have been determined between 0 and 60°C by emf measurements. Experiments were performed with unbuffered cells without liquid junction using the quinhydrone electrode as the H +-sensitive electrode.

Resampling of soil profiles in south-west Sweden for pH measurements

Abstract Seventy-four soil profiles in old spruce, beech and oak stands at Tönnersjöheden Experimental Forest were sampled both in 1927 and 1982–83. Each new profile was located within about one metre of the sampling point from 1927. Samples were collected from the A0, A2, B and C horizons down to a depth of 70 cm in mineral soil. Both in 1927 and 1982–83, pH in the soil samples was measured potentiometrically (quinhydrone electrode). The new pH-measurements were also made with a glass electrode. Today, lower pH-values were obtained in all sampled soil horizons compared with 1927. The decline in pH is 0.3–0.9 units in the humus layer and 0.3–0.7 units in the mineral soil.

Some potentiometric studies in propvlene carbonate Application of hydrogen and quinhydrone electrodes and evaluation of proton medium effect from ferrocene assumption

Results of standardization of Hg/HgCl2(s) electrode in propylene carbonate (vs. NHE) are presented for possible use of the sytem in routine potentiometric measurements in the particular solvent. Also, using suitable cells along with the said Hg/HgCl2(s) reference electrode standard potentials of the reactions Fc++eFc and quinone + 2 H++2ehydroquinone have been determined. The proton medium effect on the basis of the ferrocene assumption is found to be 5.5.

Some potentiometric studies in propylene carbonate: Application of hydrogen and quinhydrone electrodes and evaluation of proton medium effect from ferrocene assumption

Results of standardization of Hg/HgCl 2(s) electrode in propylene carbonate (vs. NHE) are presented for possible use of the sytem in routine potentiometric measurements in the particular solvent. Also, using suitable cells along with the said Hg/HgCl 2(s) reference electrode standard potentials of the reactions Fc ++ eFc and quinone + 2 H ++2 ehydroquinone have been determined. The proton medium effect on the basis of the ferrocene assumption is found to be 5.5.

Reference electrodes for use in the potentiometric determination of chloride. Part II. Quinhydrone electrodes

Download options Please wait... Article information DOI https://doi.org/10.1039/AN9840900445 Article type Paper Download Citation Analyst, 1984,109, 445-452 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Reference electrodes for use in the potentiometric determination of chloride. Part II. Quinhydrone electrodes D. Midgley, Analyst, 1984, 109, 445 DOI: 10.1039/AN9840900445 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Derek Midgley

Thermodynamics of ionization of trans-crotonic and adipic acids in water; the silver – silver adipate electrode

The ionization constant, K, of trans-crotonic acid, and the first and second ionization constants, K1 and K2, of adipic acid have been determined in water at seven different temperatures ranging from 15 to 45 °C with the help of the cells without liquid junction using silver – silver chloride and quinhydrone electrodes. The variations of pK, pK1, and pK2 with temperature have been expressed by the equations[Formula: see text]and[Formula: see text]From the temperature coefficient of the ionization constants, the standard enthalpy, entropy, Gibbs energy, and heat capacity changes of the corresponding dissociation processes have been calculated. Using the values of ionization constants of adipic acid, the standard potential of the Ag(s)/Ag2Ad(s)/Ad2− electrode, and the related standard thermodynamic quantities for the electrode process[Formula: see text]have been calculated in water at those temperatures.

Biamperometric end-point detection with quinhydrone electrodes in coulometric neutralization titrations in nonaqueous media

Some new possibilities for continuous coulometric titration of bases, alone and in mixture, as well as of mineral acids, alone and in mixture, were investigated with acetic anhydride-anhydrous acetic acid as solvents. The titration end point was determined biamperometrically. It was established that quinhydrone electrodes with platinum, palladium, and gold as the metal phase can be equally satisfactorily applied to the end-point determination of both the titrations of bases or acids alone, and of their two-component mixtures. Amounts of 6–10 μequiv. of bases, i.e., 20–47 μequiv. of mineral acids, were determined with the maximal average deviation of 1.4%. Results of biamperometric determinations of bases are compared to those of catalytic thermometric determinations, while those of acids are compared with the results of photometric titrations. The agreement between the methods is satisfactory.

Low impedance pH sensitive electrochemical devices that are potentially applicable to transcutaneous PCO2 measurements.

Two cases of low impedance, non-glass membrane electrodes for pH measurement were evaluated: (I) Metal--metal oxide electrodes and (II) Reduction-oxidation electrodes. The fundamental cause of oxygen sensitivity of metal-metal oxide electrodes were examined and three approaches for its suppression were proposed. For the case of Sb--Sb2Ox electordes, oxygen sensitivity can be attenuated partially by cell loading, either directly across the reference electrode or indirectly across a third slave electrode. In a PO2 range of 8--54 kPa, more than 95% of the PO2 response can be suppressed by loading the cell emf to half of tis open-circuit value. The oxygen sensitivity also was observed to diminished by grinding the metal-metal oxide and pressing it under high pressure into a pellet electrode. Other metal-metal oxide electrodes that have promise in transcutaneous measurement are the Pd-PdO2 electrodes. The redox electrodes are typified by the Quinhydrone electrode. A membrane Quinhydrome electrode showed a sensitivity of 56 mV/Decade at 37 degree C and no oxygen sensitivity up to 50 kPa and a drift of 1 mV/h over a 24-h period. However, the stability deteriorated over a long-term period.

Thermodynamic properties of actinide complexes Part V. Uranyl(VI)-thioglycolate system; thorium(IV)-glycolate and -thioglycolate systems

The changes in free energy, enthalpy and entropy for the formation of uranyl (VI)-thioglycolate, thorium(IV)-glycolate and -thioglycolate complexes have been determined. The changes in free energy were calculated from the stability constants, obtained from a potentiometric determination of the concentration of free hydrogen ion, using a glass or quinhydrone electrode. The enthalpy values were measured calorimetrically. The measurements were performed at 25.0°C in an aqueous sodium perchlorate medium with the total sodium concentration equal to 1.00 M. A comparison of the magnitude of the enthalpy and entropy changes for the various systems gives additional support of the view that the thioglycolate acts as a monodentate ligand while the glycolate forms chelate rings.

Projection maps for the determination of equilibrium constants

Projection maps are suggested for the construction of model functions to be compared with potentiometric measurements of the free ligand concentration. The theoretical curves are found to be a valuable guide in the choice of the optimal conditions for the evaluation of complex formation equilibria. As an example, measurements of [H + ], with a quinhydrone electrode, have been planned with the help of model maps for the study of the protolysis of oxalic acid in 1 M(KCl) at 25°C. Projection maps are also proposed to interpret data obtained by the method of competitive reactions.

ChemInform Abstract: STUDIES ON THE APPLICATION OF THE QUINHYDRONE ELECTRODE IN FORMAMIDE. VII. THE IONIZATION CONSTANTS AND RELATED THERMODYNAMIC QUANTITIES OF (E)‐CINNAMIC ACID FROM E.M.F. MEASUREMENTS AT DIFFERENT TEMPERATURES

Chemischer InformationsdienstVolume 7, Issue 46 Article ChemInform Abstract: STUDIES ON THE APPLICATION OF THE QUINHYDRONE ELECTRODE IN FORMAMIDE. VII. THE IONIZATION CONSTANTS AND RELATED THERMODYNAMIC QUANTITIES OF (E)-CINNAMIC ACID FROM E.M.F. MEASUREMENTS AT DIFFERENT TEMPERATURES U. N. DASH, U. N. DASHSearch for more papers by this author U. N. DASH, U. N. DASHSearch for more papers by this author First published: November 16, 1976 https://doi.org/10.1002/chin.197646096AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue46November 16, 1976 RelatedInformation

The carbon electrode in potentiometric titrations

The use of the carbon electrode in place of the conventional platinum electrode and quinhydrone electrode offers an attractive alternative in certain types of potentiometric work and the present ar...

Deuterium isotope effects on the ionization of the lower carboxylic acids in water and deuterium oxide

To facilitate the interpretation of isotope effects on the ionization of weak acids in water and deuterium oxide, a comparison of these quantities with that for a standard acid is proposed. Therefore, a quantity Kr has been defined by the equation Kr = (kH/kD)/(kH′/KD′). The equilibrium constants KH and KD refer to the ionization constants in water and deuterium oxide respectively. The equilibrium constant KX′(X = H, D) refers to the acid used as a reference. An equation is derived from which it may be concluded, that for a series of acids closely similar in geometry and force field around the acidic group, a value of Kr close to unity should be obtained. To test this prediction the values of KH/KD for a series of n-alkanoic acids (N = 3–6) are compared experimentally with the value of KH/KD of acetic acid (25 °C). An emf method has been used in these measurements (quinhydrone electrode). In agreement with the theory a value for Kr close to unity has been observed.

Coulometric bipotentiometric titration of bases and their mixtures in acetic anhydride in the presence of two pretreated metal (Au, Pd)- quinhydrone electrodes

The possibility of application of gold and palladium as the metal phase of quinhydrone electrodes in coulometric bipotentiometric titrations of bases alone and of some of their two-component mixtures in acetic anhydride was investigated. The effect of activation of these electrodes, by heating in an alcohol flame, on the shape of the titration curve is discussed. The amounts of bases determined were 5.0–10.0 μeq. Errors did not exceed ±2%.

Titration of fluoride with lanthanum chloride applying the biamperometric and the bipotentiometric end-point detection

The possibilities of the biamperometric as well as of the bipotentiometric end-point determination in the titration of potassium fluoride with lanthanum chloride using pairs of antimony, bismuth, tin and quinhydrone electrodes (metal phase platinum, palladium and gold) were investigated. In unbuffered fluoride solutions which contained 75 % of ethanol at the titration end-point, an amount of 5.72 mg of KF was determined with an average deviation of <0.8%. The results obtained are compared with those of the potentiometric titration proving a good agreement.

Coulometric bipotentiometric titration of bases and their mixtures in acetic anhydride using a polarized pair of quinhydrone electrodes

Coulometric bipotentiometric titration of bases and their mixtures in acetic anhydride using a polarized pair of quinhydrone electrodes