Analytical chemistry in the Netherlands

Summary A general review is given of analytical chemistry in the Netherlands. The following points are discussed: education, professional organisations, research, funding of research, international activities, analytical control in practice.

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Analytische Chemie in den Niederlanden

Zusammenfassung Ein allgemeiner Überblick über die Analytische Chemie in den Niederlanden wird gegeben. Die folgenden Themen werden diskutiert: Ausbildung, Berufsorganisationen, Forschung, Finanzierung der Forschung, internationale Aktivitäten, analytische Kontrolle in der Praxis.

     

Investigation of pyrite oxidation by hexavalent chromium: solution species and surface chemistry

Pyrite oxidation processes by aqueous Cr(VI) were investigated at 25 degrees C under an argon atmosphere. Synthetic pyrite suspensions (6 g L(-1)) were reacted for 20 h with a range of Cr(VI) solutions from 0 to 700 microM and at pH 2-12. The main objective of this work was to investigate the reaction mechanisms by emphasizing the role of sulfur species. Aqueous chemical processes were well illustrated in acidic media where significant amounts of sulfate and iron species were determined. Sulfate anions are the final stable sulfur species involved in the reaction pathway. Experiments showing complete Cr(VI) removal from solution displayed ratios [S(VI)]/[Fe](tot)<2, probably due to a deficit in aqueous sulfur species. Experiments showing incomplete Cr(VI) removal displayed ratios [Cr(VI)](removed)/[S(VI)] close to 1.5. This ratio was found to be consistent with the formation of thiosulfate (S(2)O(2-)(3)). Thiosulfate ions disproportionated into elemental sulfur S(0) and tetrathionate ions (S(4)O(2-)(6)) that were finally oxidized to sulfate anions under acidic conditions. The distribution of the oxidation state of sulfur atoms at the pyrite surface determined by XPS was additional evidence for the multistep sulfur oxidation process. The presence of elemental sulfur in the S(2p) spectra correlated well with the disproportion of thiosulfate under acidic conditions.     

Analytical chemistry in Hungary

Summary The past and present state of analytical chemistry in Hungary are reviewed in this paper. The publications by Hungarian authors are briefly analysed and the relationship of Hungarian and international activity in the field is discussed.

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Analytische Chemie in Ungarn

Zusammenfassung Ein überblick über Vergangenheit und Gegenwart der analytischen Chemie in Ungarn wird gegeben. Die Veröffentlichungen ungarischer Autoren werden kurz besprochen und die Beziehungen zur internationalen Entwicklung werden diskutiert.