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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Geometriae dedicata 58 (1995), S. 313-326 
    ISSN: 1572-9168
    Keywords: 51M10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper we find conditions in order to construct hyperbolic right-angledN-gons with the lengths ofN-3 sides given. Explicit formulae for the length of a side in terms of the lengths ofN-3 non-adjacent sides are obtained.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-5073
    Keywords: titanium determination ; 3,4-dihydroxybenzoic acid ; spectrophotometry ; geological matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A fast Spectrophotometric method has been developed for titanium determination in geological matrices, based on the mixture of the sample solution with an exact volume of a single chromogenic solution containing acetate buffer, ascorbic acid and 3,4-dihydroxybenzoic acid DHB, which forms with titanium(IV) ions a yellow complex with absorption maximum at 380 nm. The following parameters were studied: complex stability, pH effect, amount of DHB, amount of acetate buffer, obedience to Beer's law, amount of ascorbic acid and iron masking. The results demonstrated that titanium can be determined in the pH range 4.0–5.0, with a molar absorptivity of 1.43 × 104 1·mol−1 cm−1 and a limit of detection of 2.3 ng/ml. The methodology that allows analysis of 30 samples per hour. Common anions and cations do not interfere, even when present in large amounts. Iron(III) interference can be easily eliminated by reduction to iron(II) using ascorbic acid. Analytical characteristics of the proposed procedure, such as calibration sensitivity, analytical sensitivity, limit of detection and coefficient of variation, were determined. The procedure was applied for titanium determination in various standard geological matrices, with results of satisfactory accuracy and precision (RSD〈1%).
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-5073
    Keywords: 2-(2-thiazolylazo)-p-cresol ; titanium determination ; simultaneous determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction between titanium(IV) and 2-(2-thiazolylazo)-p-cresol-(TAC) in aqueous methanol media at apparent pH 4.0–5.6 results in a intensely coloured complex that is stable for at least 2 h. The combining ratio is 1 ∶ 1 cation ∶ TAC. Beer's law is obeyed up to 5.0 μg/ml titanium(IV) at 580 nm. The apparent molar absorptivity at 580 nm is 9.82.103 l.mole−1.cm−1 and the detection limit obtained was 5 ng/ml titanium (IV). A spectrophotometric method for the simultaneous determination of titanium and iron with TAC is proposed.
    Type of Medium: Electronic Resource
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