CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry

 

Volume 49 No. 3 September 2000

 

Elemental composition of humic and fulvic acids in the epipedon of some Estonian soils; 131–144 (full article in PDF format)

Loit REINTAM, Jüri KANN, Tiiu KAILAS, and Raja KÄHRIK

Abstract. The elemental composition of active humic and fulvic acids, bound with mobile sesquioxides, was studied in the mollic epipedon of Rendzic Leptosols and arable Calcari–Chromic Luvisols of different ages, as well as in the umbric epipedon of forest Stagnic Luvisols. In general, no essential differences were observed in the elemental composition of humus acids in the studied soils. A particularly uniform and stable composition of both humus acids is characteristic of the mollic epipedon of Rendzic Leptosol with age differences up to 7000 years, while the compositions of humic and fulvic acids are similar with only H content being more expressed in fulvic acids. The humic acids of the umbric epipedon of forest Luvisol have not changed with time either. However, an increase in the content of C, H, and N, accompanied by a decrease in the O content, has taken place in fulvic acids after clear-cutting, and obvious changes have occurred in their structural and chemical status. In the mollic epipedon of arable Luvisols, only a slight tendency of decrease in the content of C and N, and an increase in the O content of humic acids has developed during three decades as a result of alternating application of extensive and intensive management in agriculture. An evident decrease in the content of C, H, and N, accompanied by an increase in the O content, is opposite to changes in forest soils and appears to be common for the impacts of a cereal monoculture and weak agrotechnology on soil humus in general. The elemental composition of humic acids in all studied Luvisols was the following: C 53–56%, N 4–5%, H about 6%, O 33–36%, and C : N 10.7–14.5. The respective data for fulvic acids were: C 35–50%, N 2.5–4.5%, H 3–7%, O 40–58%, and C : N 10.2–18.6.

Key words: elemental composition, humus acids, Luvisol, Rendzic Leptosol.

 

Physical and chemical properties of ionic liquids based on the dialkylimidazolium cation; 145–155 (full article in PDF format)

Mihkel KOEL

Abstract. Thermogravimetric curves and IR and UV–VIS spectra were measured for 1-butyl-3-methylimidazolium based ionic liquids. The solubility of ionic liquids in several organic solvents was determined.

Key words: room temperature molten salts, ionic liquids, IR spectra, UV–VIS spectra, thermogravimetry, solubility of ionic liquids.

 

Polarography and stripping voltammetry of lead–polycarboxylate complexes on dropping mercury and rotating disc electrodes; 156–167 (full article in PDF format)

Heldur KEIS, Jaanus KRUUSMA, and Janne PULLAT

Abstract. The influence of counterion charge, concentration, and pH of the solution on the complex formation of Pb²⁺ with polymethacrylic acid (PMA) and polyacrylic acid (PAA) was studied by different polarographic techniques. Titration of a polarographically detectable metal such as Pb²⁺ with polyacids allows precise determination of the apparent formation (stability) constant K of the complex through analysis of current data. It is shown that calculated and graphically determined values of K are in good agreement for experiments on dropping mercury and rotating disc electrodes. Linear relationships between log K and log a (activity of the counterion) were obtained and slope values characterizing the exchange ratio in the complex between Pb²⁺ and counterion were - 0.5 (K⁺) and – 1.2 (Ca²⁺), respectively. Studies at different pH values within the range 3.5–7 showed increasing stability constant with increasing pH. Slopes of log K vs. pH plots determined using different polarographic techniques were 0.5 ± 0.05 for PAA–K⁺, PMA–K⁺, and PMA–Ca²⁺ and 0.65 ± 0.05 for PAA–Ca²⁺.

Key words: voltammetry, complexing of heavy metals, polycarboxylic acids.

 

Catalytic filtration for the improvement of drinking water quality; 168–179 (full article in PDF format)

Yelena VERESSININA, Marina TRAPIDO, Viktor AHELIK, and Rein MUNTER

Abstract. Model solutions on the basis of Tallinn drinking water containing 3.79 ± 1.34 mg/L of total iron were treated with different filter media, such as Birm, Pyrolox, Manganese Greensand (all based on manganese dioxide), Crystal Right (a zeolite), and sand. The results of the study indicated that all these filter media removed iron from water and influenced other water quality parameters. Crystal Right had the best adsorption capacity among the filter media mentioned above. The sand filter removed also oxidized iron.

Key words: drinking water, catalytic filtration, filter media, ferrous iron, ion content.

 

 

 

CHRONICLE

Hugo Raudsepp 100; 180–181 (full article in PDF format)