Potentiometric determination of potassium ferricyanide

A rapid and accurate electrometric method for the determination of potassium ferricyanide solutions has been investigated. It consists in titrating ferricyanide solutions potentiometrically against standard AgNO₃, using a silver indicator electrode in conjunction with a saturated calomel electrode connected by a KNO₃ bridge. Either of the reagents may be used as the titrant. A marked change in e.m.f is observed at thc end-point corresponding to the formation and precipitation of Ag³[Fe(CN)₆]. The curves have a regular form, a pronounced maximum in dE/dV occurs at the end-point and the results are very accurate and reproducible. The reaction, though simple, affords a quantitative method for the determination of ferricyanide or silver. The effect of neutral salts and ethanol on the accuracy of the end-point has been studied.     

Spectrophotometric determination of novalgin in tablets by use of potassium iodate

An indirect colour reaction has been studied for determination of novalgin in tablets. The method is simple, rapid and reproducible with a relative standard deviation of 0.2%. Novalgin is determined spectrophotometrically by means of its colour reaction with potassium iodate. Beer's law is obeyed over the range 1-10 mg of drug. A tentative reaction mechanism has been proposed.     

Potentiometric determination of potassium cations using a nickel(II) hexacyanoferrate-modified electrode

Electroactive nickel(II) hexacyanoferrate (NiHCF) thin film modified electrodes are effective potentiometric sensors for the determination of potassium ions. The NiHCF films are deposited onto glassy carbon electrodes by repetitive potential cycling in K(3)Fe(CN)(6)/NaNO(3)/Ni(NO(3))(2) solution. The modified electrodes exhibit a linear response to potassium ions in the concentration range 1x10(-3) to 2.0 mol dm(-3), with a near-Nernstian slope (45-49 mV per decade) at 25 degrees C. In the determination of potassium ion in syrups used for treatment of potassium deficiency, the NiHCF-modified electrode gave comparable results to those obtained using flame emission spectrophotometry.     

Potentiometric determination of tetraphenylborate ions with silver nitrate. Determination of silver, potassium and thallium(I)

Summary The potentiometric determination of tetraphenylborate with silver nitrate solution was investigated a) at i=0 in the presence of calomel reference electrode and silver resp. silicone rubber based halide-selective indicator electrodes and b) at i0 in the presence of silver (cathode)-calomel, silver-silver, silver-platinum, platinum-silver and graphite-silver electrode couples. An indirect method is described for the determination of potassium ions with potentiometric end-point indication. Experiments were also carried out in order to develop methods for the titration of silver, potassium and thallium(I) ions with sodium tetraphenylborate solution in the presence of anodic polarized graphite and calomel reference electrodes. The relative standard deviations were 0.38–0.49% for tetraphenylborate, 1.96% for potassium and 1.07% for thallium(I).

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Potentiometrische Bestimmung von Tetraphenylborationen mit Silbernitrat. Bestimmung von Silber, Kalium und Thallium(I)

Zusammenfassung Die Möglichkeit der potentiometrischen Bestimmung von Tetraphenylborat mit Silbernitrat wurde untersucht a) in Anwesenheit von Kalomel-Bezugselektrode und Silber- bzw. haloidselektiven Silicongummi-Indicatorelektroden bei i=0 und b) in Anwesenheit von Silber (Kathode)-Kalomel-, Silber-Silber, Silber-Platin-, Platin-Silber- und Graphit-Silber-Elektrodenpaaren bei i0. Eine Methode zur indirekten potentiometrischen Bestimmung von Kalium sowie Verfahren zur Bestimmung von Silber-, Kalium- und Thallium(I)-ionen mit Natriumtetraphenylboratlösung in Anwesenheit einer anodisch polarisierten Graphitelektrode und einer Kalomel-Referenzelektrode wurden ausgearbeitet. Die relativen Standardabweichungen betragen für Tetraphenylborat 0,38–0,49%, für Kalium und Thallium 1,96 bzw. 1,07%.

     

Determination of ascorbic acid by potassium iodate

Summary Results are given for a two stage oxidation in the ascorbic acid-KIO₃ reaction under controlled conditions of acidity. The first step corresponds to the Landolt reaction and the second end point is obtained by the classical Andrews method. The reproducibility and accuracy of the results calculated on the basis of the two successive end points constitute an interesting new feature of this redox reaction involving the use of KIO₃ as a primary standard for the determination of ascorbic acid.Our sincere thanks are due to Professor S. S. Joshi for kind interest in the work and to the National Institute of Sciences of India for award of a Research Fellowship to one of us (G. S. D.).     

On the determination of cerium(IV) by iodate and bromate

Analytical and Bioanalytical Chemistry - Determination of cerium(IV), based upon its reduction by a measured excess of KSCN solution and titration of the excess against standard iodate or bromate,...     

Radiometric redox titration of antimony(III) with potassium iodate

The redox titration of antimony(III), labeled with¹²⁵Sb(III), by potassium iodate was radiometrically investigated using the burette method and the standard series method. The stoichiometry of the redox process was determined. The redox valence (the number of equivalents per mol) of potassium iodate for the oxidation of antimony(III) to antimony(V) was found to be 6, differing from the results obtained using the usual visual indicator method, where the value was shown to be 4. This disagreement in the equivalents of potassium iodate for the oxidation of antimony(III) is discussed.     

Potentiometric determination of silver(I) by selective membrane electrode based on derivative of porphyrin.

The performance of silver metal complexes with meso-tetraphenylporphyrin ([H2T(4-CH3)]PP) as ionophores for ion-selective electrodes was studied. The electrode exhibited linear response with Nernstian slope of 59.2 +/- 1.0 mV per decade within the concentration range of 1.0 x 10(-7)-1.0 x 10(-1) M silver ions. The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot, was 1.0 x 10(-7) M. The response time of the electrode was < 10 s over the entire concentration range. The silver-selective electrode exhibited good selectivity for Ag(I) with respect to alkali, alkaline earth and heavy metal ions. The electrodes could be used at least three months without a considerable divergence in their potential. The electrodes are suitable for use in aqueous solutions in a wide pH range of 3.0-9.0. They were used as indicator electrodes in titration of Ag(I) with sodium iodide solution and were successfully applied to direct determination of silver in real samples.     

Potentiometric study of silver(I)-thiosemicarbazonates

A potentiometric method is described for the determination of thiosemicarbazones involving the formation of a complex with Ag(I). This method is proposed for thiosemicarbazones of the following carbonyl compounds: salicylaldehyde, p-hydroxybenzaldehyde, benzaldehyde, picolinaldehyde, 6-methylpicolinaldehyde and p-dimethylaminebenzaldehyde. Stability constants of the complexes are determined by Ringbom and Harju's method.

FIG. 2. Variation of pAg + logα_{PAT (H)} + log ([Ag?PAT)]/[PAT])

2. Formation Constants of the Silver-Thiosemicarbazonates

     

15.

Indirect determination of iodate by atomic-absorption spectrophotometry     

Chakraborty D  Das AK 《Talanta》1989,36(6):669-671

An indirect method for determination of trace iodate in certain high-purity chemicals by atomic-absorption spectrophotometry (AAS) is described. Iodate forms a stable ion-association complex [Hg(dipy)(2)](IO(3))(2) in neutral medium, which can be extracted into methyl isobutyl ketone with 99% efficiency. The extract can be analysed for mercury (and hence indirectly for iodate) by flameless AAS. The limit of detection for iodate by this method is 7.5 ng. Apparent recoveries of 92-112% have been obtained for spikes of 0.25-0.70 mug of iodate.     

16.

Potentiometric determination of silver(I), palladium(II) and gold(III) in mixtures by use of an iodide-selective electrode     

Mohamed Tarek Mohamed Zaki  Adel El-Sayed Mohamed 《Mikrochimica acta》1991,103(3-4):191-198

Two procedures are proposed for the potentiometric determination of Ag(I), Pd(II) and Au(III) in binary mixtures, by titration with potassium iodide solution, and use of a commercial iodide electrode as sensor. In the first procedure, two aliquots of the mixture are titrated, at pH 2.0 ± 0.2 and 9.0 ± 0.2, adjusted with dilute sulphuric acid and ammonia solution. At pH 2.0, the titrant reacts with both metals, whereas at pH 9.0, Ag(I) is the only reactant. The second procedure utilizes titration of two aliquots of the mixture in the presence and absence of a selective masking agent. The methods have been applied to the determination of these metals in some jewellery alloys.     

17.

Silver(I) undecafluorodiantimonate(V)     

Mazej Z  Benkic P 《Inorganic chemistry》2003,42(25):8337-8343

The reaction between AgBF4 and excess of SbF5 in anhydrous hydrogen fluoride (aHF) yields the white solid AgSb2F11 after the solvent and the excess of SbF5 have been pumped off. Reaction between equimolar amounts of AgSb2F11 and AgBF4 yields AgSbF6. Meanwhile, oxidation of solvolyzed AgSb2F11 in aHF by elemental fluorine yields a clear blue solution of solvated Ag(II) cations and SbF6- anions. AgSb2F11 is orthorhombic, at 250 K, Pbca, with a=1091.80(7) pm, b=1246.28(8) pm, c=3880.2(3) pm, V=5.2797(6) nm3, and Z=24. The crystal structure of AgSb2F11 is related to the already known crystal structure of H3OSb2F11. Vibrational spectra of AgSb2F11 entirely match the literature-reported vibrational spectra of beta-Ag(SbF6)2, for which a formulation of a mixed-valence AgI/AgIII compound was suggested (AgIAgIII(SbF6)4). On the basis of obtained results it can be concluded that previously reported beta-Ag(SbF6)2 is in fact Ag(I) compound with composition AgSb2F11.     

18.

Structure (neutron) of room-temperature phase III potassium iodate,KIO3     

B. W. Lucas 《Acta Crystallographica. Section C, Structural Chemistry》1984,40(12):1989-1992

     

19.

Potentiometric micro-titration of potassium     

K. J. Karrman  Einar Bladh  Per-Olof Gedda 《Mikrochimica acta》1959,47(5):775-778

Summary The potentiometric micro titration of potassium tetraphenylborate in acetone/water mixtures using a silver nitrate solution gives a sharper end-point than with indicators. The silver nitrate titer obtained against K(Ph)₄B in acetone/water mixtures varies with the acetone concentration. This applies particularly for solutions which contain less than ca. 40 Vol.% acetone.

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Zusammenfassung Die potentiometrische Mikrotitration von Kaliumtetraphenylborat in Aceton-Wasser-Gemischen mit Silbernitrat gibt einen schärferen Endpunkt als bei Verwendung eines Indikators. Der Silbernitrattiter gegen K(Ph)₄B in Aceton-Wasser-Gemischen variiert mit der Acetonkonzentration, besonders wenn der Acetongehalt der Lösungen geringer ist als 40 Vol.-%.

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Résumé Le microtitrage potentiométrique du tétraphénylborate de potassium dans des mélanges d'eau et d'acétone à l'aide d'une solution titrante de nitrate d'argent donne un point final de titrage plus net que les indicateurs. Le titre du nitrate d'argent déterminé à l'aide de K(Ph)₄B dans des mélanges acétone-eau varie avec la concentration en acétone. Cette observation s'applique particulièrement aux solutions qui contiennent moins de 40% environ en volume d'acétone.

     

20.

Thermal decomposition kinetics of potassium iodate     

K. Muraleedharan  M. P. Kannan  T. Ganga Devi 《Journal of Thermal Analysis and Calorimetry》2011,103(3):943-955

The thermal decomposition of potassium iodate (KIO₃) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential thermal analysis (DTA) of the thermal decomposition of KIO₃ was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO₃ was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of KIO₃. The non-isothermal decomposition of KIO₃ was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal decomposition of KIO₃ was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal decomposition kinetics of KIO₃ can be best described by the contracting cube equation.     

Thiosemicarbazone	Log $\text{K}{}_{\mathrm{<mtext>f</mtext>}}$
-Benzaldehyde	15.5 ± 0.1
-Picolinaldehyde	14.0 ± 0.
-6-Methylpicolinaldehyde	14.5 ± 0.
-Salicylaldehyde	15.7 ± 0.1
-p-Hydroxybenzaldehyde	15.6 ± 0.
-p-Dimethylaminebenzaldehyde	17.2 ± 0.1

Indirect determination of iodate by atomic-absorption spectrophotometry

An indirect method for determination of trace iodate in certain high-purity chemicals by atomic-absorption spectrophotometry (AAS) is described. Iodate forms a stable ion-association complex [Hg(dipy)(2)](IO(3))(2) in neutral medium, which can be extracted into methyl isobutyl ketone with 99% efficiency. The extract can be analysed for mercury (and hence indirectly for iodate) by flameless AAS. The limit of detection for iodate by this method is 7.5 ng. Apparent recoveries of 92-112% have been obtained for spikes of 0.25-0.70 mug of iodate.     

Potentiometric determination of silver(I), palladium(II) and gold(III) in mixtures by use of an iodide-selective electrode

Two procedures are proposed for the potentiometric determination of Ag(I), Pd(II) and Au(III) in binary mixtures, by titration with potassium iodide solution, and use of a commercial iodide electrode as sensor. In the first procedure, two aliquots of the mixture are titrated, at pH 2.0 ± 0.2 and 9.0 ± 0.2, adjusted with dilute sulphuric acid and ammonia solution. At pH 2.0, the titrant reacts with both metals, whereas at pH 9.0, Ag(I) is the only reactant. The second procedure utilizes titration of two aliquots of the mixture in the presence and absence of a selective masking agent. The methods have been applied to the determination of these metals in some jewellery alloys.     

Silver(I) undecafluorodiantimonate(V)

The reaction between AgBF4 and excess of SbF5 in anhydrous hydrogen fluoride (aHF) yields the white solid AgSb2F11 after the solvent and the excess of SbF5 have been pumped off. Reaction between equimolar amounts of AgSb2F11 and AgBF4 yields AgSbF6. Meanwhile, oxidation of solvolyzed AgSb2F11 in aHF by elemental fluorine yields a clear blue solution of solvated Ag(II) cations and SbF6- anions. AgSb2F11 is orthorhombic, at 250 K, Pbca, with a=1091.80(7) pm, b=1246.28(8) pm, c=3880.2(3) pm, V=5.2797(6) nm3, and Z=24. The crystal structure of AgSb2F11 is related to the already known crystal structure of H3OSb2F11. Vibrational spectra of AgSb2F11 entirely match the literature-reported vibrational spectra of beta-Ag(SbF6)2, for which a formulation of a mixed-valence AgI/AgIII compound was suggested (AgIAgIII(SbF6)4). On the basis of obtained results it can be concluded that previously reported beta-Ag(SbF6)2 is in fact Ag(I) compound with composition AgSb2F11.     

Potentiometric micro-titration of potassium

Summary The potentiometric micro titration of potassium tetraphenylborate in acetone/water mixtures using a silver nitrate solution gives a sharper end-point than with indicators. The silver nitrate titer obtained against K(Ph)₄B in acetone/water mixtures varies with the acetone concentration. This applies particularly for solutions which contain less than ca. 40 Vol.% acetone.

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Zusammenfassung Die potentiometrische Mikrotitration von Kaliumtetraphenylborat in Aceton-Wasser-Gemischen mit Silbernitrat gibt einen schärferen Endpunkt als bei Verwendung eines Indikators. Der Silbernitrattiter gegen K(Ph)₄B in Aceton-Wasser-Gemischen variiert mit der Acetonkonzentration, besonders wenn der Acetongehalt der Lösungen geringer ist als 40 Vol.-%.

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Résumé Le microtitrage potentiométrique du tétraphénylborate de potassium dans des mélanges d'eau et d'acétone à l'aide d'une solution titrante de nitrate d'argent donne un point final de titrage plus net que les indicateurs. Le titre du nitrate d'argent déterminé à l'aide de K(Ph)₄B dans des mélanges acétone-eau varie avec la concentration en acétone. Cette observation s'applique particulièrement aux solutions qui contiennent moins de 40% environ en volume d'acétone.

     

Thermal decomposition kinetics of potassium iodate

The thermal decomposition of potassium iodate (KIO₃) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential thermal analysis (DTA) of the thermal decomposition of KIO₃ was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO₃ was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of KIO₃. The non-isothermal decomposition of KIO₃ was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal decomposition of KIO₃ was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal decomposition kinetics of KIO₃ can be best described by the contracting cube equation.