Ion-exchange behaviour of pyridinium tungstoarsenate

The exchange behaviour of pyridinium tungstoarsenate has been investigated with some uni and bivalent cations. The compound shows high specificity towards Cs(+) and Ag(+) and the exchange is complete even in the low concentration range. The slopes of the isotherms of various cations are widely different suggesting that separation of these ions on a pyridinium tungstoarsenate column is feasible. From a linear plot of Barrer's equation, the thermodynamic equilibrium constant, the energy of interaction between the ions on the surface and the free energy change of the process have been evaluated.     

Ion-exchange behaviour of metals on deae-cellulose in methanol-thiocyanate-hydrochloric acid media

Only a few metals can be adsorbed on DEAE-cellulose from aqueous thiocyanate-chloride media. However, several metal ions, including Cu(II), Zn, Cd, In, Bi and U(VI), exhibit enhanced adsorption on DEAE-cellulose from methanol-thiocyanate-hydrochloric acid mixtures. The distribution coefficients for these metals are given as functions of methanol, ammonium thiocyanate and hydrochloric add concentration. Differences in adsorption among metals permit many useful separations, including those of two-, three- and four-component mixtures, on short columns containing 1-1.5 g of DEAE-cellulose.     

Potassium bis(ethylenediamine)­copper(II) ferricyanide

The title compound, potassium bis(ethylenediamine‐N,N′)copper(II) hexacyanoferrate(III), K[Cu(C₂H₈N₂)₂]‐[Fe(CN)₆], contains [Cu(en)₂]²⁺ and [Fe(CN)₆]^3? complex ions, where en is ethylenediamine. The Fe^III and K⁺ ions lie on twofold axes and the Cu^II atom lies on an inversion center. The [Cu(en)₂]²⁺ ion has square‐planar coordination with a mean Cu—N distance of 1.992 (2) Å and the [Fe(CN)₆]^3? ion has distorted octahedral coordination with a mean Fe—C distance of 1.947 (2) Å.     

Electrochemical behaviour of alkaline copper complexes

A search for non-cyanide plating baths for copper resulted in the development of alkaline copper complex baths containing trisodium citrate [TSC] and triethanolamine [TEA]. Voltammetric studies were carried out on platinum to understand the electrochemical behaviour of these complexes. In TSC solutions, the deposition of copper involves the slow formation of a monovalent species. Adsorption of this species obeys Langmuir isotherm. In TEA solutions the deposition involves the formation of monovalent ions obeying the non-activated Temkin isotherm. Conversion of divalent to monovalent copper is also slow. In TEA and TSC alkaline copper solutions, the predominant species that undergo stepwise reduction contain only TEA ligands.     

Ion-exchange chromatography

A review is given of variables which affect the separation factors in ion-exchange chromatography. In favorable cases the influence of complex formation, pH, and eluant concentration can be predicted by simple calculations, whereas the interaction forces inside the resin phase are still largely unexplored.     

The existence of ferrous ferricyanide

Evidence in the literature on the synthesis of ferrous ferricyanide is critically discussed. Pyrolysis and pressure effects on Prussian Blue lead to ferrous ferrocyanide together with decomposition by-products, and not to ferrous ferricyanide. The latter compound could be a precursor in the formation of Turnbull's Blue or an excited state of Prussian Blue, but it is not a stable chemical species.     

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.     

Ion-exchange cellulose techniques

Summary Ion-exchange celluloses have been used for the separation of biochemicals with ionic character for a number of years. Paper and thin-layer forms of the materials have, up to the present, mainly been applied to the separation of small molecules rather than polyelectrolytes. Column materials, however, are now available specifically designed to handle large molecules. This communication compares the three ion-exchange techniques and outlines the latest methods for extracting the high resolving power inherent in the new types of cellulose column materials available.

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Zusammenfassung Seit einigen Jahren werden Cellulose-Ionenaustauscher zur Trennung biochemischer Substanzen mit Ionencharakter benutzt. In der Form von Papieren und Dünnschichten wurden diese Materialien hauptsächlich zur Trennung kleiner Moleküle eingesetzt. Jetzt sind jedoch Säulenfüllmaterialien erhältlich, die speziell für große Moleküle geeignet sind. Die drei Arbeitsmethoden werden verglichen und neue Verfahren aufgezeigt, die es gestatten, das hohe Auflösungsvermögen der neuen Materialien auszunutzen.

     

Thermal behaviour of hydrated copper(II) complexes

Dehydration steps of aquacopper(II) complexes with homogeneous and heterogeneous coordination sphere are investigated from the view point of structural changes taking place under their heating to the decomposition temperature and during the dehydration. The role of loosening of intra-and intermolecular hydrogen bonds in the decomposition reaction for the structure changes of the remainder, the structural presumptions of the reactants for lower hydrates formation are discussed. Activation parameters of dehydration were found to be the lower, the smaller are the structure differences between the reactants and products. They do not reflect the bond length central atomvolatile ligand, much more the overall structure differences between the starting and resulting compounds. From all data on crystal and molecular structures of dehydrated compounds is the reaction pathway best indicated by anisotropic temperature parameters of donor atoms corrected for the thermal movement of the central atom: the higher these values in the bond direction are, the lower the values of activation energies of dehydration are.     

Determination of ascorbic acid with ferricyanide

Ascorbic acid can be determined by titration with potassium ferricyanide in sulphuric, phosphoric or hydrochloric acid media. Twelve indicators, including ferroin and some triphenylmethane and thiazine dyes, have been found suitable. The method has been successfully applied to assay of commercial products for vitamin C. Several organic substances likely to be associated with ascorbic acid in preparations and plant tissues do not interfere.     

Sorption behaviour of rubidium,thallium and silver on chromium ferricyanide gel binary separations of Rb+ and Tl+

Sorption behaviour of monovalent Rb⁺, Tl⁺ and Ag⁺ is studied on chromium fericyanide gel. Log K_d vs log concentration plots show that Rb⁺ and Tl⁺ are sorbed through ion exchange mechanism in a higher concentration range of ammonium nitrate or nitric acid, whereas the adsorption of Ag⁺ is irreversible. It was found possible to elute Rb⁺ and Tl⁺ on the columns of this gel by 4 mol dm⁻³ NH₄NO₃ and 10 mol dm⁻³ HNO₃, respectively. Binary separations of Rb⁺ and Tl⁺ from a number of other metal ions were achieved as other ions were found practically unadsorbed on these columns and were eluted with water of pH 2–3. Achieved separations are of radioanalytical and analytical importance.     

Oxidation of formate by alkaline ferricyanide

Summary A catalytic oxidation of formate by alkaline ferricyanide has been studied. To the formate solution an excess of ferricyanide and osmium tetroxide as catalyst were added and the excess ferricyanide was back titrated with arsenious oxide using the amperometric dead stop end point method. The method is superior to the oxidative determination of formate by alkaline permanganate.

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Zusammenfassung Formiat kann durch katalytische Oxydation mit alkalischer Hexacyanoferrat(III)-lösung bestimmt werden, indem man die Probelösung mit einem Überschuß des Reagenses sowie Osmiumtetroxid als Katalysator versetzt und den Überschuß mit Arsen(III)-lösung zurücktitriert.Der Endpunkt wird nach der Dead stop-Methode bestimmt. Das Verfahren ist der Oxydation mit alkalischer Permanganatlösung überlegen.

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Sincere thanks of the authors are due to Prof. G. B. Singh for providing the necessary facilities. The award of a U.G.C. Scholarship to one of them (A.L.J.R.) is also acknowledged.     

Oxidation of thiocyanate by alkaline ferricyanide

Summary Oxidation of KSCN by alkaline K₃Fe(CN)₆ in presence of osmic acid has been studied quantitatively. The reaction proceeds at a measurable rate at ordinary temperature but is accelerated on refluxing the system on a water bath for a short time. The stoichiometry of the redox process suggests the formation of cyanate and sulphate as the products of oxidation. The quantity of thiocyanate is calculated by estimating the ferrocyanide formed and the ferricyanide consumed in terms of Ce(SO₄)₂ and Na₂S₂O₃ respectively. A kinetic study of the above reaction is under investigation.Sincere thanks of the author are due to Prof. S. S. Joshi for facilities and kind interest in the work. The award of a Scientific Man Power Committee Research Scholarship is also gratefully acknowledged.     

A spot test for ferricyanide

Summary 0.02 g/0.2 ml of potassium ferricyanide can be detected on a spot plate by utilising its catalytic effect on the reaction of cerium (III) with sulphosalicylic acid. A probable mechanism is discussed.

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Zusammenfassung Die katalytische Wirkung von Hexacyanoferrat(III) auf die Reaktion zwischen Cer(III) und Sulfosalicylsäure wird zur einem empfindlichen Tüpfelnachweis für [Fe(CN)₆]^3– benutzt. Noch 0,02 g/0,2 ml können nachgewiesen werden. Der Reaktionsmechanismus wird diskutiert.