Proceedings of the Estonian Academy of Sciences

CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry

Volume 53 No. 3 September 2004

Xylidine-polluted groundwater purification. Ozonation and catalytic wet oxidation; 97–115

Janek Reinik and Juha Kallas

Abstract. This paper discusses the removal of xylidines from polluted waters by means of chemical oxidation methods. Xylidines, persistent compounds of rocket fuel, have been detected in high concentrations in groundwater in the areas of former Soviet missile bases. To treat such groundwater, two chemical processes, ozonation and catalytic wet oxidation, were studied. The kinetics of degradation of 2,4-xylidine by ozonation was investigated in a wetted-wall column. A laboratory-scale ozone–water contact column was designed and a steady-state wetted wall reactor model was developed. The ozonation model with the estimated parameters showed good agreement between predicted and experimental data. The estimated reaction rate coefficients could be used for the design of a bubble ozonation column for xylidine-polluted groundwater treatment. The developed model and experimental set-up can be used in the future to estimate the kinetic parameters of ozonation reactions involving other similar compounds. Catalytic wet oxidation was carried out in a stirred batch autoclave in the presence of granulated activated carbon. 2,4-Xylidine was concentrated on the surface of the granulated activated carbon and then oxidized at different temperatures (140–170 °C) and oxygen partial pressures (4–10 atm). The GAC type catalyst was active enough for 2,4-xylidine oxidation, but not for the oxidation of the formed organic acids. Degradation of organic acids needs severer conditions. Both chemical oxidation processes could be used as a pre-treatment before biological treatment. The results of this paper can be used to design two chemical processes for purification of xylidine polluted water.

Key words: 2,4-xylidine, ozonation, wetted wall column, catalytic wet oxidation, mathematical modelling, reaction kinetics.

Kinetics of [³H]WAY100635 binding to 5-HT_1A receptors in rat hippocampal membranes; 116–124

Sven Parkel and Ago Rinken

Abstract. The binding of [³H]-N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide ([³H]WAY100635) to 5‑HT_1A receptors in rat hippocampal membranes was studied. Saturation experiments showed that [³H]WAY100635 binds to a single class of binding sites with very high affinity (K_D = 87 ± 4 pM, B_max = 15.1 ± 0.2 fmol/mg protein). The binding of [³H]WAY100635 was reversible, but slow. The dissociation of [³H]WAY100635 from its complex with 5-HT_1A receptors was characterized with the k_off = (7.8 ± 1.1) × 10^–3 min^–1, which means that at low concentrations of the radioligand equilibrium cannot be achieved before 7 h incubation at 25 °C. The obtained data indicate that [³H]WAY100635 is a valuable tool for the determination of the number of 5-HT_1A receptor binding sites, but the determination of its affinity is complicated as it hardly reaches equilibrium at concentrations close to its K_D.

Key words: [³H]WAY100635, 5-HT_1A receptor, equilibrium, kinetics, affinity, rat hippocampus.

Gottfried Wilhelm Osann and ruthenium; 125–144

Helvi Hödrejärv

Abstract. Gottfried Wilhelm Osann (1797, Weimar – 1866, Würzburg) was chemistry professor at Tartu University (Universitas Dorpatensis) in 1823–1828. In that period he analysed the crude platinum received from the Ural Mountains and discovered a new platinum metal. He named this metal ruthenium after the medieval name of Russia in Latin. As the quantity of the new element he had was small he could not isolate the metal. This was done several years later and published in 1844 by Carl Claus in Kazan, Russia. Claus is often mentioned as the discoverer of ruthenium and G. W. Osann is forgotten.

Key words: G. W. Osann, ruthenium, discovery of chemical element.

Instructions to authors; 145–148