Iodine--iodide reference electrode for potentiometric titrations of bases in acetic acid

The suitability of the half-cell Pt/I2, KI in glacial acetic acid as reference electrode for potentiometric titrations of weak bases in the same medium was investigated. This electrode is easily prepared. It has been found very convenient in use and performing at least as well as the best electrodes used for the same purpose. Some phenomenological aspects of the behaviour of the above half-cell, of interest for the use as the reference electrode in the laboratory practice have been observed, that show important differences respect aqueous medium and other organic solvents.     

Coulometric-acidimetric titrations in anhydrous acetic acid

A technique for the coulometric generation of hydrogen ions in an acetic acid-acetic anhydride-sodium perchlorate electrolyte by anodically oxidizing a mercury electrode is described. Accurate coulometric titrations of sodium acetate and potassium hydrogen phthalate have been carried out. The technique should be applicable to many of the basic substances which can be titrated volumet-rically in acetic acid.     

The aluminium indicator electrode in acid-base potentiometric titrations

Aluminium has been employed as an indicator electrode in potentiometric acid-base titrations. The titration curves obtained were approximately 3.6 times broader than those obtained with the antimony electrode.     

Polypyrrole-calcion film as a membrane and solid-contact in an indicator electrode for potentiometric titrations

This paper shows the application of conducting polymers (CPs) for constructing potentiometric indicator electrodes. Two types of polypyrrole (PPy)-based calcium sensors are presented, one sensor with PPy-calcion film as the active part and the other sensor with PPy-calcion as a solid-state contact coated with a conventional membrane selective towards calcium ions. It is shown that the PPy-calcion film, due to the complexing properties of calcion ensuring high loading of the film with calcium, is sufficiently selective to be used as the active part or as a mediating layer of the indicator electrode. The electrode, with PPy-calcion film as the active part, was used as the indicator electrode in potentiometric titrations of calcium in mixed solvents, where conventional PVC-based electrode can not be used. For the first time, the practical applicability of PPy-based electrodes in titrations is demonstrated.     

Natural monocrystalline pyrite as electrode material for potentiometric titrations in water

The possibility of applying natural monocrystalline pyrite as sensor for the potentiometric titration of acids in water was investigated. The potential of this electrode in aqueous solutions exhibits a sub-Nernst dependence. In fresh solutions the slope (mV/pH) is 33.9. The potential jumps at the titration end-point obtained in titrations of HCl, H(3)PO(4) and CH(3) COOH do not differ much from those obtained by the application of the glass electrode as the indicator one. The potentials in the course of the titration and at the titration end-point (TEP) are rapidly established. The results obtained in the determination of the investigated acids deviated for 0.16-0.34% with respect to those obtained by using the glass electrode as the indicator one.     

Anodically generated cobalt(III) acetate as reagent for coulometric titrations in acetic acid

Summary Conditions for the anodic generation of cobalt(III) acetate with high current efficiency in non-aqueous solutions of potassium acetate in acetic acid have been investigated. The presence of water or acetic anhydride in the anolyte diminishes the amount of the generated oxidant. The stability of the generated cobalt(III) acetate solution is decreased in the presence of water and at elevated temperatures. Procedures for coulometric titrations of reducing substances with cobalt(III) acetate, using the biamperometric or the potentiometric end point detection, are described.Presented at the Fifth European Conference on Analytical Chemistry-EUROANALYSIS V, Cracow, Poland, August 26–31, 1984.     

Behaviour of membrane graphite electrodes in potentiometric titrations of reducing substances with bromine in acetic acid

A platinum electrode, a Radelkis OP-C-7111D graphite electrode and a laboratory-prepared silicone-rubber-based membrane graphite electrode were used in potentiometric titrations of reducing substances with bromine in acetic acid. In determinations of hydroquinone, 2-methylhydroquinone, 2-chlorohydroquinone and ascorbic acid, the Radelkis electrode showed the greatest sensitivity. The advantage of the laboratory-prepared membrane graphite electrode lay in its rapid attainment of stable potential values. Titrations were improved by addition of potassium acetate to the solutions analysed. The effects of water and acetic anhydride on the results were also investigated.     

On the use of the mercury electrode in chelatometric potentiometric titrations

Summary Information is given on the applicability of the mercury electrode in chelatometric potentiometric titrations. The influence of ternary complex formation, the formation of precipitates on the electrode and possible errors, due to the asymmetric shape of the titration curves are discussed.

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Über die Verwendung der Quecksilberelektrode bei chelatometrisch-potentiometrischen Titrationen

Zusammenfassung Einige Betrachtungen werden angestellt über die Anwendung der Quecksilberelektrode für komplexometrische Titrationen mit potentiometrischer Endpunktsanzeige. Der Einfluß der Bildung ternärer Komplexe, die Bildung von Niederschlägen auf der Elektrode und die Fehler infolge der Asymmetrie der Titrationskurven werden besprochen.

     

Voltammetric,potentiometric and amperometric studies with a rotated aluminum wire electrode: The R.Al.E. as indicator electrode in potentiometric and amperometric acid-base titrations

The effect of varying concentrations of fluoride on the potential of the R.AI.E. in acid buffer solutions is reported. In the pH range between 1 and 5.5 the potential becomes 30 mV more negative per unit increase in pH at fluoride concentrations between 10^-3 and 10^-4M. At a given pH the potential becomes 100 mV more negative when the fluoride concentration is increased from 10^-4 to 10^-3it. No depolarization occurs and no reproducible potentials can be measured in phosphate buffers of pH 6 to 8, even in the presence of 10^-3M fluoride. This concentration of fluoride causes depolarization and establishment of reproducible potentials in veronal buffers of reproducible pH 6 to 8. At a pH greater than 9 fluoride has no effect on the electrode potential which now becomes determined by pH. In the presence of fluoride, oxygen shifts the electrode potential to less negative values (mixed potential). Examples of potentiometric and amperometric titrations of strong and weak acids are given with the R.AI.E. as indicator electrode.     

Electrically generated lead(IV) acetate and manganese(III) acetate as reagents for coulometric redox titrations in acetic acid

Summary The conditions were investigated for electrochemical generation of lead(IV) acetate in acetic acid by oxidation of lead(II) acetate on a lead dioxide electrode and on a platinum electrode. Bivalent manganese ions are quantitatively oxidized on a platinum electrode to the tervalent state in the same solvent. Coulometric titration methods for the determination of small amounts of hydroquinone in acetic acid were developed on the basis of the electrically generated oxidizing agents. Better results were obtained in titration with electrogenerated manganese(III) acetate. The titration end-point was detected by the biamperometric method. Suitable redox indicators were found.

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Zusammenfassung Die Bedingungen zur elektrochemischen Pb(IV)-Acetatherstellung aus Pb(II)-Acetat in Eisessig durch Oxydation an der Blei(IV)-oxid-Elektrode und an der Pt-Anode wurden untersucht. Auch Mn(II)-Ionen wurden in diesem Lösungsmittel quantitativ zu Mn(III) an der Pt-Elektrode oxydiert. Mit diesen auf elektrochemischem Wege erhaltenen Oxydationsmitteln wurden coulometrische Titrationsmethoden für die Bestimmung kleiner Hydrochinonmengen ausgearbeitet. Bessere Resultate wurden mit Mn(III)-Acetat erhalten. Die Endpunktbestimmung wurde durch biamperometrische Anzeige oder mit Hilfe visueller Redoxindikatoren durchgeführt.

     

Equivalence volumes in potentiometric titrations

The development of methods for finding the equivalence volume by using linear regression methods is reviewed. The methods discussed are mainly those developed and used at the Department of Analytical Chemistry at the Royal Institute of Technology in Stockholm. No attempt has been made to cover the large number of methods of finding the equivalence volume in potentiometric titrations developed elsewhere.     

Construction of a permanganate ion-selective electrode and its application to potentiometric titrations

The construction of a liquid-membrane type permanganate ion-selective electrode and its application to potentiometric titrations are described. The benzylcetyldimethylammonium-permanganate ion-pair in the aqueous phase is easily extracted into nitrobenzene and the extract is employed as the liquid ion-exchange membrane of the ion-selective electrode. The electrode gives Nernstian response to permanganate in the concentration range from 10(-6) to 10(-1)M, and the potential is almost independent of pH over the range from 3.0 to 10.5. The electrode can be used as indicator electrode in potentiometric titrations with permanganate.     

Differential potentiometric titrations of binary mixtures of halides with two ion-selective indicator electrodes

Differential potentiometric titrations with two different ion-selective indicator electrodes are described. Ion-selective electrodes for Cl^-, Br^-, I^-, F^-, S^2-, as well as glass and silver billet electrodes were used. The method was tested in the determination of binary mixtures of halides (Cl^-, Br^-, I^-, and F^-) by titration with solutions of silver nitrate, alone and mixed with lanthanum or thorium nitrate as required. Various factors influencing the determination were investigated. Results of simultaneous determinations of mixtures were in good agreement with the results of separate determinations within certain concentration limits. The method was successfully applied to the determination of a four-component halide mixture. Titrations of mixtures of fluoride with thiocyanate or hexacyanoferrate(III), and some other possibilities, are also reported.     

Iodine monochloride in anhydrous acetic acid as an oxidizing agent

A systematic study of the redox reactions of iodine monochloride with various inorganic ions in glacial acetic acid medium is described. Sodium sulphite, mercury(I) perchlorate, antimony trichloride, arsenic trichloride and iron(II) perchlorate were examined. Potentiometric and amperometric methods were used to follow the reduction of iodine monochloride, which yields different products according to the type of reductant.     

N-chlorophthalimide as a new oxidant for direct titrations in aqueous acetic acid medium

A stable new oxidimetric titrant, N-chlorophthalimide in anhydrous acetic acid, is proposed for direct titrations of a variety of simple and complex reductants such as As(III), Sb(III), Fe(II), ferrocyanide, iodide, ascorbic acid, hydroquinone, hydrazine, phenylhydrazine, benzhydrazide, isonicotinic acid hydrazide, semicarbazide, thiourea, aniline, phenol, oxine and its metal complexes, and anthranilic acid and its metal complexes.     

Melaminium acetate acetic acid solvate monohydrate

The crystals of the title new melaminium salt, 2,4,6‐tri­amino‐1,3,5‐triazin‐1‐ium acetate acetic acid solvate monohydrate, C₃H₇N₆⁺·CH₃COO^?·CH₃COOH·H₂O, are built up from singly protonated melaminium residues, acetate anions, and acetic acid and water mol­ecules. The melaminium residues are interconnected by N—H?N hydrogen bonds to form chains along the [010] direction. These chains of melaminium residues form stacks aligned along the a axis. The acetic acid mol­ecules interact with the acetate anions via the H atom of their carboxylic acid groups and, together with the water mol­ecules, form layers that are parallel to the (001) plane. The oppositely charged moieties interact via multiple N—H?O hydrogen bonds that stabilize a pseudo‐two‐dimensional stacking structure.     

Coulometric redox titrations of hydrazine,phenylhydrazine and isoniazid with electrogenerated lead(IV) acetate and manganese(III) acetate in acetic acid

Summary The conditions fox coulometric determination of small quantities of hydrazine, phenylhydrazine and isoniazid in glacial acetic acid with electrogenerated manganese(III) acetate and lead(IV) acetate were investigated. With the direct coulometric method at room temperature, good results were obtained in the determination of hydrazine and isoniazid with lead(IV) acetate and in the determination of phenylhydrazine with manganese(III) acetate. Hydrazine and isoniazid can also be determined by the coulometric back-titration method if the oxidation with manganese(III) acetate is performed at elevated temperature.

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Zusammenfassung Die Bedingungen für die coulometrische Bestimmung kleiner Mengen Hydrazin, Phenylhydrazin und Isoniazid mit elektrolytisch erzeugtem Mangan(III)-Acetat und Blei(IV)-Acetat in Eisessig wurden untersucht. Bei Zimmertemperatur wurden gute Resultate durch direkte coulometrische Titration des Hydrazins und Isoniazids mit Blei(IV)-Acetat und bei Titration des Phenylhydrazins mit Mangan(III)-Acetat erhalten. Durch coulometrische Rücktitration können bei höheren Temperaturen Hydrazin und Isoniazid mit Mangan(III)-Acetat erfolgreich bestimmt werden.

     

Chitosan-cellulose sulfate acetate complexation in acetic acid solutions

Colloidal and optical properties of dispersions of chitosan-cellulose sulfate acetate interpolyelectrolyte complexes resultant from mixing dilute solutions of the polymers in acetic acid and in acetic acid-based buffer mixtures are investigated. It is established that, in acetic acid, an insoluble complex is formed whose composition corresponds to the unit ratio [chitosan]: [cellulose sulfate acetate] = 1: 1.5, mol/mol. Particle size and concentration are independent of the order of mixing of the solutions of the polymers. In buffer solvents, the particle size is larger and the particle concentration is lower than those in acetic acid. Excess chitosan causes the dissolution of the complex. The addition of low-molecular-weight electrolytes to ionic strengths of 0.2–0.3 also promotes the dissolution of the interpolyelectrolyte complex. The complex becomes completely soluble at ionic strengths of 1.5–2.0.     

Calculated equivalence volume in potentiometric acid-base titrations

Summary Using a pH meter, a motorized burette and a programmable pocket calculator potentiometric acidbase titrations may be carried out with a high degree of precision, a high degree of accuracy and in a time comparable to the time needed to perform a titration with a visual indicator. With the exception of the lowest concentration of the weak acid a precision higher than 0.01 ml of the reagens is easily obtainable, whereas the accuracy may be as high as 0.1 %. The method is suitable over a wide range of concentrations of either strong or weak acids.

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Berechnetes Äquivalenzvolumen bei potentiometrischen Säure-Base-Titrationen

Zusammenfassung Mit Hilfe eines pH-Meßgeräts, einer Motorbürette und einem programmierbaren Taschenrechner können potentiometrische Säure-Base-Titrationen mit hoher Reproduzierbarkeit und Richtigkeit in einer mit der Verwendung von visuellen Indicatoren vergleichbaren Zeit durchgeführt werden. Mit Ausnahme der niedrigsten Konzentration einer schwachen Säure wurde eine Reproduzierbarkeit von besser als 0,01 ml und eine Richtigkeit von 0,1 % erhalten. Das Verfahren ist für einen weiten Konzentrationsbereich von starken und schwachen Säuren geeignet.