Dichromate titration of thallium(I)

The formal redox potentials of the thallium(III)-thallium(I) couple in different acids of varying strengths are reported. The minimum concentration of hydrochloric acid required for a direct titration of thallium(I) with potassium dichromate is 5M. Thallium(I) can be titrated directly with the primary standard oxidant, potassium dichromate, at room temperature, with ferroin as indicator, in 6M hydrochloric acid. Atmospheric oxygen must be excluded.     

Determination of ascorbic acid in fruits and pharmaceuticals by titration with thallium(III)

Summary Ascorbic acid has been determined in fruits and pharmaceuticals by titration with thallium (III) sulfate using promethazine or 4-me-thoxychrysoidine as visual indicators or by potentiometry. Interference of cysteine, glutathione and hydrogensulfite is avoided by their masking with acrylonitrile. Use of cysteine or hydrogensulfite is recommended as an antioxidant during the extraction of ascorbic acid from plant materials.

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Bestimmung von Ascorbinsäure in Früchten und Arzneimitteln durch Titration mit Thallium(III)

Zusammenfassung Die potentiometrische Titration von Ascorbinsäure in Früchten und Arzneimitteln mit Thallium(III) läßt sich unter Verwendung von Promethazin oder 4-Methoxychrysoidin als Indikator durchführen. Die Störung durch Cystein, Glutathion und Hydrogensulfit läßt sich durch Maskierung mit Acrylnitril verhindern. Cystein oder Hydrogensulfit dienen als Antioxydantien bei der Extraktion der Ascorbinsäure aus pflanzlichem Material.

     

(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.     

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).     

Trimethylsilylmethyl derivatives of thallium(III)

Some trimethylsilylmethyl derivatives of thallium(III) have higher stability and unusual coordination behavior in comparison with simple alkylthallim(III) analogs for steric reasons.     

Complexometric titration of gallium, indium and thallium(III) using sodium azide as a metal indicator

Summary Thallium(III) has been determined between pH 4.0 and 6.0 by titration against EDTA using sodium azide as indicator. The metal ion gives a bright yellow colour which is discharged at the equivalence point. Micro-quantities upto about 1 mg of the metal have been determined with accuracy. The end-point has also been determined photometrically. Gallium(III) and indium(III) can also be determined by back-titration of the excess of EDTA added to each of these ions against a standard ferric chloride solution using sodium azide as indicator.

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Zusammenfassung Thallium(III) wird durch Titration mit ÄDTA-Lösung bei pH 4,0–6,0 gegen Natriumazid als Indicator bestimmt. Der Umschlag am Endpunkt erfolgt von Gelb nach Farblos. Mikromengen bis zu 1 mg können mit guter Genauigkeit erfa\t werden. Die Bestimmung kann auch photometrisch durchgeführt werden. Gallium(III) und Indium(III) können durch Rücktitration von überschüssigem ÄDTA mit Eisen(III)-chloridlösung bestimmt werden, wobei ebenfalls Natriumazid als Indicator dient.

     

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.     

Photometric titration of titanium(III) with iron(III)

An oxidimetric titration of titanium(III) with iron(III) with a photometric end-point is proposed. Acetylacetone was used to obtain an intensely coloured titanium(III) complex; titanium(III) was formed by prereduction with chromium(II) or vanadium(II). Amounts of titanium down to 35 μg were determined with fairly good accuracy and precision. Few common elements interfere.     

Tin(II) sulphate as a new reductimetric titrant--direct titration of thallium(III) with use of ion-pair and redox indicators

The use of tin(II) sulphate as a direct reductimetric titrant for thallium(III) has been investigated, with potentiometric and visual detection of the end-point. Some azure dyes are used as redox indicators and Methylene Blue is used as both a redox and an ion-pair indicator.     

Reaction of grayanotoxin-II with thallium (III) nitrate

Reaction of grayanotoxin-II (1) with thallium nitrate gave 3(S), 20-epoxy-6 (S), 14 (R), 16 (R)-trihydroxy-5-oxo-5, 10-seco-ent-kaur-1 (10) -ene (2). The structure of 2 was elucidated by the X-ray diffraction analysis of its reduction product (3).     

Oxidation of trans-alloocimene by thallium(III) nitrate

We have obtained 2,7-dimethoxy-2,7-dimethyl-3,5-octadiene by the action of thallium(III) nitrate on trans-allo-ocimene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1087–1089, May, 1990.     

Reaction of neorl with thallium(III) perchlorate

Reaction of nerol ($\text{1}$) with thallium(III) perchlorate gave 6-oxabicyclo[3.2.1]octane derivatives ($\text{2}$) and ($\text{3}$), and 6,9-dioxabicyclo[3.3.1]nonane derivatives ($\text{4a–d}$) as the cyclization products.     

Sequential oxidimetric determination of thallium(I) and (III)

The reaction between thallium(III) and oxalic acid in sulphuric acid medium has been investigated. Spectrophotometric results show that thallium(III) can be quantitatively reduced to thallium(I) with oxalic acid in aqueous medium when heated to near boiling point. Conditions for the estimation of the excess of oxalic acid with cerium(IV) sulphate in the presence of thallium(I) and for the estimation of a mixture of thallium(I) and thallium(III) have been investigated. The method is simpler than many other redox methods reported for the determination of thallium(III) and is free from many interferences encountered in these titrations. The reagents are cheap and quite stable.     

Oxidation of 4-chromanones with thallium(III) nitrate

Treatment of 4-chromanones 1a-g with thallium(III) nitrate in acidic methanol results mainly in dehydrogenation, whereas α-methoxylation and/or Taylor-McKillop rearrangement predominate in trimethyl orthoformate. The mechanistic features of these oxidations are briefly discussed.     

Photochemical reduction of thallium(III) with hydrogen peroxide

A convenient method for determination of thallium(III) is based on photochemical reduction with hydrogen peroxide in the presence of bromide as catalyst, followed by oxidation of thallium(I) with potassium bromate.