Solvent extraction studies of radioisotopic exchange of36Cl with Chloramine-B in strong acid medium

Exchange studies with³⁶Cl and Chloramine-B in strong acid medium revealed that the extent of exchange is less than that occurs at pH 3.3 indicating the formation of a new species of Chloramine-B which is not participating in the exchange reaction and this has been confirmed by conductometric titration of Chloramine-B with dilute solutions of H₂SO₄, HCl, HClO₄ and CH₃COOH.     

Extent of exchange of bromine-82 with bromamine-T in strong acid medium

The extent of exchange of bromine-82 with bromamine-T in strong acid medium is low due to the formation of at lower acid concentrations and bromine at higher acidities. formation occurs over a narrow acid concentration range and is less stable than .     

Electrochemical reduction of isonicotinic amide in a strong acid medium

Isonicotinic amide was studied by dc and DP polarography and linear sweep cyclic voltammetry in a strong acid medium (pH < 3). Tafel slopes and reaction orders were obtained at potentials corresponding to the foot of the polarographic wave.In a very strong acidic medium the process occurs through the formation of a protonated gem-hydroxylamine which is transformed into the aldehyde via a substitution by water, which is the rate-determining step. For 0 < pH < 3, the gem-hydroxylamine formed after two reversible electron transfers can eliminate an ammonia molecule in two ways: (a) proton-catalysed substitution by water followed by the formation of a hydrated aldehyde; and (b) non-catalysed elimination to form the free aldehyde. The limiting current of the wave is partially controlled by these concurrent chemical reactions and. consequently, the process appears as ECE.     

Anion exchange of some elements in acetic acid-hydrochloric acid medium

A comparative study of the adsorbability of Cd(II), Ni(II), Mn(II), Ga(III), La(III), Mo(VI) and bromide from aqueous acetic acid solutions on' Dowex 1-X8, 100–200 mesh, in the acetate and chloride forms, proved that chloride ions are indispensable for high adsorption from concentrated acetic acid solutions. A study of the adsorption isotherms of Ni(II), Mn(II) and Cd(II) on the acetate-form resin from acetic acid-hydrochloric acid solutions, showed that these elements form anionic complexes. The K_d values on RCl-exchanger, for a given acetic acid concentration, were highly dependent on the total exchange capacity of the resin. A simplified anion-exchange separation procedure in aqueous acetic acid was developed, with an adsorption step from a mixture of acetic and hydrochloric acids.     

Diffusion coefficient of 36Cl in silver chloride

Diffusion coefficient of 36Cl in silver chloride was revealed to be about 1 x 10(-10)-4 x 10(-11) cm2 . s-1 in the range of 400 degrees C-200 degrees C by means of radioactive tracer measurements. Activation energy for diffusion was calculated about 0.13 eV. These results were different from those obtained by Maurer and Compton.     

Exchange studies of 5-sulphosalicylic acid in amberlite IRA 401 Cl anion exchange resin

Exchange studies of 5-sulphosalicylic acid in Amberlite IRA 401 Cl anion exchange resin have been carried out at 25°C in a stirred vessel. The exchange rates have been interpreted on the basis of a simple diffusion model.     

Titrimetric determination of iron (II) with potassium bromate in a strong phosphoric acid medium with a potentiometric end-point

Summary The use of a strong orthophosphoric acid medium enables a direct titration of iron(II) to be made at room temperature (in an inert atmosphere) with potassium bromate using a potentiometric endpoint. Various organic substances like oxalate, tartrate, citrate, sucrose and glucose do not interfere. The method is, therefore, likely to be important for the determination of ferrous and ferric iron in pharmaceutical products.

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Zusammenfassung Die direkte Titration von Eisen(II) mit Kaliumbromat kann in stark phosphorsaurer Lösung bei Zimmertemperatur (in inerter Atmosphäre) mit potentiometrischer Endpunktsbestimmung durchgeführt werden. Organische Verbindungen wie Oxalat, Tartrat, Citrat, Saccharose und Glucose stören nicht. Das Verfahren könnte daher bei der Eisen(II)- und Eisen(III)-bestimmung in Arzneimitteln Verwendung finden.

     

Distribution coefficients for twelve elements in oxalic acid medium on a strong anion-exchange resin

The distribution coefficients were determined for twelve elements, namely As(III), Ce(III), Cr(III), Co(II), Cu(II), In(III), Lu(III), Mn(II), Hg(II), Mo(VI), Sc(III) and Zn(II), on a strong base anion exchanger in pure oxalic acid solutions. The K_D curves are given. A scheme was developed for the chromatographic separation of five elements, namely As(III), Mn(II), Co(II), Zn(II) and Cu(II). Ce(III) can be separated from Lu(III).     

Analysis of 36Cl in Savannah River Site radioactive waste

The present work shows the activity levels of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that ⁴⁰K and ²²⁸Ra concentration is nearly uniform throughout the studied area while ²²⁶Ra and ¹³⁷Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of ²²⁶Ra/²²⁸Ra ratio (0.72) in the sediments indicates that ²³⁸U has relatively greater solubility and mobility than ²³²Th. Similarly, low activity ratio (0.18) for ¹³⁷Cs/⁴⁰K reflects the presence of very high content of ⁴⁰K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between ²²⁶Ra and ²²⁸Ra and ¹³⁷Cs and ⁴⁰K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.     

Anomalous strong exchange narrowing in excitonic systems

We investigate theoretically the phenomenon of exchange narrowing in the absorption spectrum of a chain of monomers, which are coupled via resonant dipole-dipole interaction. The individual (uncoupled) monomers exhibit a broad absorption line shape due to the coupling to an environment consisting of a continuum of vibrational modes. Upon increasing the interaction between the monomers, the absorption spectrum of the chain narrows. For a non-Markovian environment with a Lorentzian spectral density, we find a narrowing of the peak width [full width at half maximum (FWHM)] by a factor 1∕N, where N is the number of monomers. This is much stronger than the usual 1/√N narrowing. Furthermore, it turns out that for a Markovian environment no exchange narrowing at all occurs. The relation of different measures of the width (FWHM, standard deviation) is discussed.     

Kinetics of hydrogen isotope exchange in molecules with strong intramolecular hydrogen bonds

Rate constants and activation energies of hydrogen exchange in solution between methanol and molecules with intramolecular H-bonds have been measured. It has been established that the rate-determining step is the dissociation of this bond.

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H-. , .

     

Anodic stripping voltammetry with medium exchange in trace element speciation

The application of medium exchange in anodic stripping voltammetry (ASV) was investigated by determing the fractions of ASV-labile copper, lead, cadmium and zinc in the presence of a variety of natural and sysnthetic ligands in a soft water. Pristin and polluted samples of river water were also tested. Medium exchange, where the test solution is replaced after electrodeposition by a simple electrolyte such as acetate buffer, before the oxidation (stripping) of the deposited metals, can ensure that the ASV-labile metal fraction depends only on the parameters of the electrodeposition step. Significant differences were found for ASV-labile fractons when medium exchange was used for the two river water samples, and for several mertal/ligand combinations such as copper/chloride, copper/humic acid, and zinc/tannic aid. It is recommended that medium exchange be used routinely for ASV-labile determinations.     

A titration of a strong tribasic acid with a strong triacidic base

Hexacyanocobaltic acid, H₃[Co(CN)₆], a strong tribasic acid, has been titrated potentiometrically with hexamminocobali hydroxide, [Co(NH₃)₆](OH)₃, and with triethylenediaminocobalti hydroxide, [Co(en)₃](OH)₃, both strong triacidic bases.     

Synthesis,characteristics and adsorption properties of polyphenylene sulfide based strong acid ion exchange fiber

A novel strong acid ion exchange fiber (HO₃S‐BC‐XDC‐PPS) was prepared via crosslinking and grafting copolymerization of 1,4‐bischloromenthyl benzene (XDC), benzyl chloride (BC) on polyphenylene sulfide (PPS) matrix, as well as following sulfonation reaction. The physicochemical structures and properties of the fibrous ion exchanger were characterized with Fourier transform infrared, scanning electron microscopy, thermogravimetric analysis, elementary analysis and chemical titration, respectively. Compared with the preparation of traditional polypropylene–styrene–divinylbenzene‐based ion exchange fibers, the synthesis strategy of PPS‐based strong acid ion exchange fiber avoided the complicated irradiation grafting process with ⁶⁰Co or other radiation facilities. Owing to the existing of thioether (Ar―S―Ar) and sulfoxide (―SO―) unit in fibrous matrix, a super‐equivalent adsorption phenomenon for Cu(II) ion was observed. The HO₃S‐BC‐XDC‐PPS fiber possessed high exchange capacity (≥3.0 mmol/g) and excellent thermostabilities, and the exchange capacity and desorption rate were not decreased after six adsorption desorption cycles. Copyright © 2014 John Wiley & Sons, Ltd.