Spectrophotometric determination of thallium as thallium tetriodide

Iodide ions react with thallic ions at pH 2–8 to form a complex iodide, which is suitable for the spectrophotometric determination of thallium. The reaction has a sensitivity of 0.05 μg Tl per cm² for log $\text{I}{}_0\text{I}$ = 0.001 and obeys Beer's law up to 40 p.p.m. Optimum conditions for the reaction have been established. The standard deviation is 0.6%. The effects of temperature and pH, the ratio of thallium to reagent, stability of the complex, its conformity to Beer's law, and the rate of color formation were studied. The effect of many diverse ions was examined.     

Some studies on thallium oxalates. VI

The effect of the thallium(I) concentration on the potentiometric titration of thallium(III) with oxalic acid in 0.1M HNO₃ or 0.05M H₂SO₄ is studied, and conditions are established for the preparation of the thallium(I) bis-oxalato diaquo thallate(III) complex. Chemical analysis of the salt corresponds to the formula T1^I(T1^III(C₂O₄)₂) · 5 H₂O. Thermal decomposition studies on the complex using TG, DTG and DTA techniques indicate the formation of thallium(I) oxalate (stable from 130° to 320°) as the intermediate, the final product being a mixture of thallium(I) oxide and thallium(III) oxide (stable from 520° to 600°). Infrared absorption spectra, X-ray diffraction patterns and microscopic observations are used to characterise the complex and the intermediate.     

Polarographic determination of thallium

A polarographic method for the determination of thallium is described. The inclusion of DTPA and Triton X-100 in the supporting electrolyte shifts the waves of interfering metals to considerably more negative potentials while the thallium wave is completely unaffected. An acetate buffer of pH 4–5 is the preferred base electrolyte, because a Tl-DTPA complex is formed at higher pH values. The polarographic behaviour of the complex is described and the stability constant determined.     

Neutral thallium clusters in aqueous solutions. Pulse radiolysis study

The formation of neutral Tl₂ (λ_max = 390 nm) and Tl₄ (λ_max = 360 nm) clusters in dilute aqueous solutions of Tl₂SO₄ containing formate ions was found by pulse radiolysis. The rate constants for the recombination of Tl⁰ atoms and Tl₂ clusters are equal to 1.5·10¹⁰ L mol⁻¹ s⁻¹ and 1.0·10¹⁰Lmol⁻¹ s⁻¹ (±30%), respectively, and the extinction coefficient of Tl₂ at 390 nm is −6.0·10³ L mol⁻¹ cm⁻¹ Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2367–2369, December, 1999.     

Titrimetric determination of thallium

Summary Titrimetric determination of thallium(I) is carried out by treating the sulfate with reducing sugars in alkaline medium either at room temperature or by boiling. The metal obtained is oxidised with an excess of ferric ammonium sulphate at room temperature. The ferrous ion formed, corresponding to the thallium metal oxidised, is titrated against a standard solution of ceric sulphate using N-phenyl anthranilic acid as indicator. Metallic thallium has been observed to exist in three varieties under different conditions. The presence of potassium chloride protects the metal from aerial effects. Li⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, Cd²⁺, Zn²⁺, Be²⁺, Ni²⁺, Co²⁺, Al³⁺, and Zr⁴⁺ interfere with the determining but Pb²⁺ and Th⁴⁺ do not.

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Zusammenfassung Zur maßanalytischen Bestimmung von Thallium(I) behandelt man zunächst dessen Sulfat in alkalischem Medium mit reduzierenden Zuckern bei Raumtemperatur oder im Sieden. Das dabei entstandene elementare Metall wird mit überschüssigem Eisen(III)-ammoniumsulfat bei Raumtemperatur oxydiert und die äquivalente Menge Eisen(II) mit einer Standardlösung von Cersulfat gegen N-Phenylanthranilsäure als Indikator titriert. Metallisches Thallium liegt je nach den vorliegenden Bedingungen in drei verschiedenen Formen vor und wird durch Kaliumchlorid gegen Lufteinwirkung geschützt. Li⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, Cd²⁺, Zn²⁺, Be²⁺, Ni²⁺, Co²⁺, A1³⁺ und Zr⁴⁺ stören die Bestimmung im Gegensatz zu Pb²⁺ und Th⁴⁺.

     

Photolysis of thallium azide

Preliminary treatment of TlN₃(A) with light (λ = 365 nm, I > 1 × 10¹⁴ quantum cm⁻² s⁻¹) in a vacuum (1 × 10⁻⁵ Pa) at 293 K led to the formation of a new long-wave region of spectral sensitivity. The products of photolysis of TlN₃(A) thallium and nitrogen formed in the stoichiometric ratio on the sample surface. The topography and kinetics of thallium accumulation were determined, and the effective rate constants for photolysis evaluated. Measurements of the contact voltage, current-voltage characteristics, and photocurrent showed that the photolysis of thallium azide resulted in the formation of TlN₃(A)-Tl (photolysis product) microheterogeneous systems. A model of photolysis of TlN₃(A) was suggested. According to this model, photolysis included the generation, recombination, and redistribution of nonequilibrium charge carriers in the contact field and the formation of the end products of photolysis. The limiting stage of photolysis of TlN₃(A) was the diffusion of interstitial thallium cations toward the neutral (T _n Tl _m )⁰ center. Original Russian Text ? E.P. Surovoi, L.I. Shurygina, L.N. Bugerko, N.V. Borisova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 784–790.     

The gravimetric determination of thallium(i) as thallium(i) tetraphenylboron

A gravimetric method for the determination of thallium(I) as thallium(I) tetraphenylboron has been developed. The method compares favorably with the classical chromate method. The effect of acid concentration and interference by other metal ions was studied as well as the thermal stability of the precipitate.     

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).     

The polarographic determination of thallium

A polarographic method is described for the determination of thallium in sodium triphosphate supporting electrolyte. The incorporation of 0.1% camphor in the electrolyte displaces the cathodic steps of many interfering ions, e.g., lead(II), copper(II), iron(III) and bismuth(III) to a more negative potential (1?.0 V), well away from the thallium step which remains unaffected.     

Relativistic calculations on thallium hydride

The spectroscopic parameters of the ground state of thallium hydride are obtained using the four-component relativistic Dirac–Coulomb–Gaunt–coupled-cluster wave function with single and double excitations and an estimated triples correction method. Core correlation effects make the bond weaker but have little effect on the bond length. Inclusion of the distance dependence of the Gaunt part of the two-electron Breit interaction has an opposite but smaller effect on these properties. Received: 8 September 2000 / Revised version: 5 October 2000 / Published online: 21 December 2000     

Electrochemical hydride generation of thallium

An electrochemical hydride generation (ECHG) technique was developed to improve the determination of thallium by atomic spectrometry. The technique is based on the catholyte variation system for production of thallium hydride. Using Pb-Sn alloy as cathode, a transient peak shaped signal was achieved and its height, the maximum absorbance value, was taken as an analytical parameter. Parameters that might affect the hydride generation efficiency were investigated and the analytical performance of the method under the optimized experimental conditions was assessed. The linear range was 1-250 ng mL⁻¹ for thallium and the relative standard deviation of the method was 4.2% (RSD, n = 7). The LOD for thallium was found to be 0.8 ng mL⁻¹, showing a significant improvement relative to conventional chemical hydride generation techniques. The proposed method was applied to the determination of thallium in unalloyed zinc standard reference material. This method offers high sensitivity, simplicity, rapidness, freeness from reagent and low acid consumption.     

Some studies on thallium oxalates

Two methods (the Horowitz-Metzger and the Dharwadkar-Karkhanavala) for calculating the apparent activation energies of different thallium(I) oxalates were compared. The Dharwadkar-Karkhanavala method gave consistent values.     

Nachweis von thallium mit methylviolett

Thallium can be identified by its colour reaction with methyl violet. This reaction is very sensitive and selective.