Cerimetric determination of thallium (I)

Summary The cerimetric determination of thallium(I) has been reinvestigated. A new procedure for the potentiometric titration of thallium(I) with ceric sulphate at the room temperature and at a low concentration of hydrochloric acid (1.0 N) has been developed using iodine monochloride as catalyst.The authors wish to express their grateful thanks to the Ministry of Education, Government of India, for the award of a Research Scholarship and the authorities of the Andhra University for providing research facilities.     

Dichrometric determination of thallium (I)

Summary A dichrometric procedure has now been developed for the direct volumetric titration of thallium(I), to an iodine monochloride end point. The concentration of the hydrochloric acid must be at least 7.5 N at the end point.     

Extraction separation of thallium (III) from thallium (I) with n-octylaniline

A novel method is developed for the extraction separation of thallium(III) from salicylate medium with n-octylaniline dissolved in toluene as an extractant. The optimum conditions have been determined by making a critical study of weak acid concentration, extractant concentration, period of equilibration and effect of solvent on the equilibria. The thallium (III) from the pregnant organic phase is stripped with acetate buffer solution (pH 4.7) and determined complexometrically with EDTA. The method affords the sequential separation of thallium(III) from thallium(I) and also commonly associated metal ions such as Al(III), Ga(III), In(III), Fe(III), Bi(III), Sb(III) and Pb(II). It is used for analysis of synthetic mixtures of associated metal ions and alloys. The method is highly selective, simple and reproducible. The reaction takes place at room temperature and requires 15-20 min for extraction and determination of thallium(III).     

Tetrachloroaurate(III) oxidation of thallium(I)

Summary The complementary reaction between Tl^I and AuCl _inf4 ^sup– was studied in a 3.0 mol dm^–3 HCl medium. The active species of oxidant and reductant were found to be HAuCl₄ and TlCl _inf2 ^sup– , respectively. A mechanism involving these reactive species is proposed, in agreement with the results obtained.     

Titrimetric determination of microgram amounts of thallium(I) by thiocyanate amplification after precipitation as thallium hexathiocyanatochromate(III)

Summary Thallium (5–200g) is precipitated as Tl₃Cr(SCN)₆. The precipitate is collected, then treated with 10% sodium carbonate solution, and the thiocyanate dissolved is oxidized to sulphate by iodine at pH 8.2. After acidification, the excess of iodine is extracted into chloroform, and the iodide in the aqueous solution is determined by the Leipert amplification procedure. The method provides 76 iodine atoms for each original thallium(I) ion. Copper(II), mercury(II), bismuth, lead and silver interfere seriously, the first three causing negative errors and the other two positive errors.

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Maanalytische Bestimmung von Mikrogrammengen Thallium(I) durch Vervielfachung mit Thiocyanat nach Fällung als Thalliumhexathiocyanatochromat(III)

Zusammenfassung Thallium (5–200g) wird als Tl₃Cr(SCN)₆ gefällt. Der gesammelte Niederschlag wird mit 10% iger Sodalösung behandelt und das gelöste Thiocyanat mit Jod bei pH 8,2 zu Sulfat oxydiert. Nach Ansäuern wird der Jodüberschuß mit Chloroform extrahiert und das Jodid in der wäßrigen Lösung nach Leipert titriert. Dabei entsprechen 76 Jodatome einem ursprünglichen Thallium(I)ion. Cu(II), Hg(II), Bi, Pb und Ag stören stark und verursachen negative bzw. im Falle Pb und Ag positive Fehler.

     

The application of redox and induced reactions to the determination of thallium(III) in the presence of thallium(I)

Summary A new method of the determination of thallic ions [Tl(III)] in the presence of thallous [Tl(I)] ones, based on the oxidizing properties of Tl(III) towards cysteine was proposed. Cysteine was employed as an initiator in the iodineazide reaction and the oxidized part of the initiator was eliminated from the induced reaction medium by the respective redox reaction; the reaction products do not affect the above reaction. The contents of thallic ions (50–500 ng) in the sample can be determined from the progress in the induced reaction by measuring the unreacted iodine. The relative experimental error of the determination does not exceed 6%.     

Extraction and spectrophotometric determination of thallium(III) with thiothenoyltrifluoroacetone

A procedure is described for the extractive photometric determination of thallium(III) with thiothenoyltrifluoroacetone in carbon tetrachloride. Thallium(III) is extracted quantitatively at pH 4-5 and the bright yellow extract obeys Beer's law over the Tl(III) concentration range 2.5-17.5 mug/ml, at 440 nm. Thallium(III) can be determined in the presence of a large number of cations and anions.     

Iodimetric determination of hydrazine and hydroquinone with thallium(III) solutions

SeIenium(IV) at trace levels can be determined in hydrochloric and perchloric acid solutions by alternating current and differential pulse polarography. The use of a hanging mercury drop electrode with accumulation of elemental selenium followed by cathodic stripping gives detection limits in the range 0.1–1 p.p.b. With a dropping mercury electrode the detection limit is 8 p.p.b. The possible interferences of Te(IV), Ge(IV), Cu(II), Cd(II) and Pb(II) are discussed. The serious interference of lead(II) can be prevented by addition of EDTA.     

Spectrofluorometric determination of thallium(III) with pyrogallol red and 3,4,5,6-tetrachlorofluorescein

Summary A spectrofluorophotometric determination of thallium(III) is proposed. It is based on the enhancement of the fluorescence reaction of 3,4,5,6-tetrachlorofluorescein (TCF) with Pyrogallol Red (PR) by thallium(III) in the presence of Swanol (AM 301, lauryldimethyl aminoacetic acid betain) as an amphoteric surfactant. The method was found to be suitable for the determination of thallium(III) down to 4.0 g in 10.0 ml by measuring the difference in the relative fluorescence intensities of a TCF/PR/thallium(III) solution and a TCF/PR solution. The recovery test in artificial urine was satisfactory (96±2%).     

A novel tetrachlorothallate (III)-PVC membrane sensor for the potentiometric determination of thallium (III)

A novel tetrachlorothallate (III) (TCT)-selective membrane sensor consisting of tetrachlorothallate (III)-2,3,5-triphenyl-2-H-tetrazolium ion pair dispersed in a PVC matrix plasticized with dioctylphthalate is described. The electrode shows a stable, near-Nernstian response for 1×10⁻³-4×10⁻⁶ M thallium (III) at 25 °C with an anionic slope of 56.5±0.5 over the pH range 3-6. The lower detection limit and the response time are 2×10⁻⁶ M and 30-60 s, respectively. Selectivity coefficients for Tl(III) relative to a number of interfering substances were investigated. There is negligible interference from many cations and anions; however, iodide and bromide are significantly interfere. The determination of 0.5-200 μg ml⁻¹ of Tl(III) in aqueous solutions shows an average recovery of 99.0% and a mean relative standard deviation of 1.4% at 50.0 μg ml⁻¹. The direct determination of Tl(III) in spiked wastewater gave results that compare favorably with those obtained by the atomic absorption spectrometric method. The electrode was successfully applied for the determination of thallium in zinc concentrate. Also the tetrachlorothallate electrode has been utilized as an end point indicator electrode for the determination of thallium using potentiometric titration.     

Oxidation of thallium(I) by hexacyanoferrate(III) in aqueous acetic acid

The hexacyanoferrate(III)-thallium(I) reaction in aqueous acetic acid containing large concentrations of hydrochloric acid is considerably accelerated both by hydrogen and chloride ions as well as increasing acetic acid in the medium. The experimental results obey the rate law (1) where β₁ to β₆ are the cumulative stability constants of the species TlCl, TlCl, TlCl, HFe(CN), H₂Fe(CN) and H₃Fe(CN)₆ respectively and k_a and k_b are the rate constants associated with the mono- and di-protonated oxidant species. The main active species are H₂Fe(CN) and TlCl.     

(Chloromethyl)thallium(III) compounds

Aryl(chloromethyl)thallium chlorides, Ar(ClCH₂)TlCl (Ar=C₆H₅, p-CH₃C₆H₄) have been prepared by treatment of arylthallium dichlorides with diazomethane. The derived carboxylates, Ar(ClCH₂)TlX, react with HgX₂ to give the dicarboxylates, (ClCH₂)TlX₂ (X = OCOCH₃, OCOC₃H₇-i) and with tetramethyltin to give CH₃(ClCH₂)TlX compounds. R(ClCH₂)TIX compounds (R = CH₃, C₆H₅, p-CH₃C₆H₄) undergo disproportionation in methanol to R₂TlX and (ClCH₂)₂TlX compounds.     

Influence of thallium(I) and thallium(III) on parameters of oscillating chemical reaction in a bromate-cerium(III,IV)-malonic acid-sulfuric acid system

The influence of thallium(I) and thallium(III) on the parameters of the Belousov-Zhabotinskii oscillating chemical reaction in the bromate-cerium(III, IV)-malonic acid-sulfuric acid system was studied. As a result of the addition of thallium(I) and thallium(III), the oscillation parameters change in the same way, which cannot be explained by the complexation of these ions with the bromide only. It was found that during the oscillating reaction, thallium(I) can be oxidized by bromine-containing compounds and thallium(III) reduced by the transformation products of malonic and bromomalonic acids. A scheme of action of a thallium(III)/thallium(I) two-electron redox pair in the oscillating chemical reaction studied has been proposed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 106–111, January–February, 1987.     

A [205T1]-thallium NMR study of thallium(I) and thallium(III) fluorometalates in acetonitrile

The concentration-dependent behavior observed for ²⁰⁵T1 n.m.r. resonances from thallium(I) fluorometalates, PF₆^-, WF₇^-, MoF₆^- and UF₆^-, in acetonitrile indicates that some degree of ion-pairing is present in these solutions. The paramagnetic anion, UF₆^-, has a pronounced effect on ²⁰⁵T1 resonance in the T1⁺ salt, but its effect on T1³⁺ is very small. It is suggested that T1³⁺ is effectively solvated by MeCN and that direct ion-pairing is unimportant. The ²⁰⁵T1 shielding of T1³⁺ is decreased by the presence of T1⁺ in solution, possibly as a result of the increase in asymmetry of the T1³⁺ environment.     

Radiation induced exchange reaction between thallium(I) and thallium(III)—Comparison of sulfuric acid and perchiloric acid solution

The rate constant of radiation induced exchange reaction between thallium(I) and thallium(III) ions has been studied for elucidating the mechanisms which are responsible for (T1(II) intermediates or bridging groups (SO ₄ ^2– ) in sulfuric acid and perchloric acid solutions. It was found that the radiation induced exchange reaction is accelerated by the sulfate ion, and the rate of the thallium(II)-thallium(I) reaction is faster than that of the thallium(II)-thallium(III) process in perchloric acid solution.