New compositions of fluoroindate glasses with higher chemical resistance

In this paper, glasses in the systems In-Ba-Mg and In-Ba-Zn-Sr-Mg were water leachead at 80ºC showing surface degradation after 72 hours of leaching. The extent of such degradation is determined by the solubility and the concentration of the elemental fluorides that constitute the glasses. The formation of a layer of crystallized phases on the surface of the samples was observed. Small weight losses were registered and the absence of water on the glass matrix after the attack suggested that the use of MgF2 in the systems studied can lead to better results against moisture corrosion when compared to other fluoride glasses such as the fluorozirconates.

Fontes, reatividade e quantificação de metanol e etanol na atmosfera

In the last two decades, the use of oxygenated fuels, like methanol and ethanol, pure or in mixture with gasoline, has been growing due to benefits introduced into the air quality. In Brasil, the fraction of light duty vehicles powered by pure hydrated ethanol is estimated at about 4 million, while the remaining vehicles actually utilize a mixture (22:78 v/v) of ethanol:gasoline. As a consequence, there's a need for the availability of methods that can provide the evaluation of possible impacts of alcohol emissions in the formation of chemical species in the atmosphere, as ozone, aldehydes, carboxylic acids and so on. In this paper, methanol and ethanol are discussed in their general aspects, as well as their atmospheric sources, chemical reactivity and available methods of analysis.

Perspectives in the use of carbon dioxide

The mitigation of carbon dioxide is one of the scientific and technological challenges of the 2000s. Among the technologies that are under assessment, the recovery of carbon dioxide from power plants or industrial flue gases plays a strategic role. Recovered carbon dioxide can be either disposed in natural fields or used. The availability of large amounts of carbon dioxide may open new routes to its utilisation in biological, chemical and innovative technological processes. In this paper, the potential of carbon dioxide utilisation in the short-, medium-term is reviewed.

Implementação da comunicação visual e procedimentos de conservação da obra Chemical Abstracts - Uma experiência da divisão de Biblioteca e documentação do conjunto das Químicas/USP

This paper proposes a model for visual communication, conservation, and maintenance of the collection "Chemical Abstracts". It describes the various steps for its implementation and makes considerations about the whole reference work.

Implications, large and small, from chemical education research for the teaching of chemistry

Research studies in chemical education pose a communication problem for chemists. Unlike the findings from other specializations in chemistry the findings in chemical education tend to be reported in education journals that are not readily accessible to most chemists or chemistry teachers. This lecture is an attempt to remedy this gap in communication. Research studies fall into three broad categories. (i) issues related to the content of chemistry itself, that is, What content to teach? And What meaning of each topic is to be conveyed? (ii) issues related to how chemical content is taught, such as, the role of lectures, practical work, particular pedagogies, etc. and (iii) issues related to its learning, that is, learning of concepts, conceptual change, motivation, etc. Findings in each of these categories of research over the last twenty years have drawn attention to opportunities for improving the quality of chemical education in each of the levels of formal education where chemistry is taught. Sometimes the research findings seem small since they, in fact, merely diagnose the actual problem in teaching and learning. At other times, the research findings are large because they provide a solution to these problems. What remains to be done is to disseminate the findings so that appropriate teaching occurs more widely, with its consequent gains in the quality of learning. Research findings, of these small and large types will be used to illustrate the potential of research to make the practice of chemical education more effective.

Electrochemistry and green chemical processes: electrochemical ozone production

After an introductory discussion emphasising the importance of electrochemistry for the so-called Green Chemical Processes, the article presents a short discussion of the classical ozone generation technologies. Next a revision of the electrochemical ozone production technology focusing on such aspects as: fundamentals, latest advances, advantages and limitations of this technology is presented. Recent results about fundamentals of electrochemical ozone production obtained in our laboratory, using different electrode materials (e.g. boron doped diamond electrodes, lead dioxide and DSAÒ-based electrodes) also are presented. Different chemical processes of interest to the solution of environmental problems involving ozone are discussed.

Sobre o desenvolvimento da análise volumétrica e algumas aplicações atuais

Classical methods of analysis played a fundamental role in the development of Chemistry and the chemical industry. They have been tools for analytical procedures since the 18th century, remaining useful until today. The technological appeal of the instrumental methods seems to dazzle the incoming generations of chemists who do not recognize the importance of titrimetry. A short description of the development of titrimetry is presented in order to call attention to historical landmarks for teaching and learning activities in Portuguese. A compilation of some current standard analytical methods that employ titrations is presented to illustrate the availability of titrimetry nowadays.

Chemical study of leaves of Chrysophyllum marginatum (Hook. & Arn.) Radlk (Sapotaceae)

The fractionation of the antioxidant ethyl acetate extract obtained from the dried leaves of Chrysophyllum marginatum afforded six substances identified as: alpha-amirin, gallic acid, myricitrin, quercitrin, (-)-epigallocatechin and (-)-epigallocatechin-3-O-gallate. This study contributes to the knowledge of the secondary metabolites produced by one more species of the Brazilian Flora, until now not investigated. Moreover, this study allowed the identification of three substances with antioxidant activity previously detected in this species.

Chemical composition of umbu (Spondias tuberosa Arr. Cam) seeds

The umbu tree (Spondias tuberosa Arr. Cam) is an important fruit tree the economy of the semi-arid northeastern region of Brazil. With the objective of finding use for the seeds, physical and chemical characterizations of the seeds from 2 cultivars in 2 maturation stages were carried out and their fatty acid and mineral profiles determined. The results showed no differences between the seeds analyzed. The yield was about 10% and the dimensions as follows: length from 1.48 to 2.11 cm and width from 0.76 to 1.16 cm. The average lipid content was 55% of which 69% was unsaturated and the average protein content was 24%. The seeds were a good source of the following minerals: P, K, Mg, Fe and Cu. The overall results indicated that the oil or the seeds could be used for food stuffs if no toxic agents were found.

Evaluation of seasonal changes in chemical composition and antibacterial activity of Elyonurus muticus (sprengel) O. Kuntze (Gramineae)

Aerial parts of Elyonurus muticus were collected in the four seasons of the year in the Brazilian Pantanal and subjected to extractrion with cold ethanol and to hydrodistillation. Sesquiterpenoids (E)-caryophyllene, bicyclogermacrene, spathulenol and caryophyllene oxide were the main components identified in the essential oils and their concentrations varied according to the plant collection period. The essential oils and the ethanolic crude extracts were active against Bacillus cereus MIP 96016, Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 25923 and were not active against Escherichia coli ATCC 25922. The antibacterial activities varied according to the plant collection period.

Plantas medicinais: fatores de influência no conteúdo de metabólitos secundários

Since secondary metabolites represent a chemical interface between plants and surrounding environment, their syntheses are frequently affected by environmental conditions. Thus, variations in the total content and/or of the relative proportions of secondary metabolites in plants can take place. We review the main environmental factors that can streamline or alter the production or concentration of secondary metabolites in plants. How seasonality, circadian rhythm, developmental stage and age, temperature, water availability, UV radiation, soil nutrients, altitude, atmospheric composition and tissue damage influence secondary metabolism are discussed.

Chemical constituents from Bakeridesia pickelii Monteiro (Malvaceae) and the relaxant activity of kaempferol-3-O-beta-D-(6"-E-p -coumaroyl) glucopyranoside on guinea-pig ileum

The phytochemical investigation of Bakeridesia pickelii Monteiro led to the isolation of seven compounds: beta-sitosterol, a mixture of sitosteryl-3-O-beta-D-glucopyranoside and stigmasteryl-3-O-beta-D-glucopyranoside, vanillic acid, p-coumaric acid, quercetin 3-O-beta-D-glucopyranoside (isoquercitrin) and kaempferol-3-O-beta-D-(6"-E-p -coumaroyl) glucopyranoside (tiliroside), which was isolated as the major component. Their structures were elucidated on the basis of spectroscopic data such as IR, ¹H and 13C NMR, including two-dimensional techniques. Tiliroside relaxed the guinea-pig ileum pre-contracted with KCl 40 mM (EC50 = 9.5 ± 1.0 x 10-5 M), acetylcholine 10-6 M (EC50 = 2.3 ± 0.9 x 10-5 M) or histamine 10-6 M (EC50 = 4.1 ± 1.0 x 10-5 M) in a concentration-dependent manner.

Determination of chemical elements in africanized Apis mellifera (Hymenoptera: Apidae) honey samples from the State of Piauí, Brazil

Honey is a food used since the most remote times, appreciated for its characteristic flavor, considerable nutritional value and medicinal properties; however, little information exists about the presence of chemical elements in it. The objectives of this work were to determine the chemical elements present in 38 honey samples, collected directly from beekeepers from the State of Piauí, Brazil and to verify whether they presented any contamination. The chemical elements were determined by means of Total Reflection X-ray Fluorescence. The means of three replicates were: K (109.671 ± 17.487), Ca (14.471 ± 3.8797), Ti (0.112 ± 0.07), Cr (0.196 ± 0.11), Mn (0.493 ± 0.103), Fe (1.722 ± 0.446), Co (0.038), Ni (0.728 ± 0.706), Cu (0.179 ± 0.0471), Zn (0.967 ± 0.653), Se (not detected), Br (not detected), Rb (0.371 ± 0.097), Sr (0.145 ± 0.45), Ba (11.681), Hg (not detected), and Pb (0.863) µg g-1.

Indústria química: evolução recente, problemas e oportunidades

Chemical industry underwent a significant upturn in the past few years. In Brazil, the position of this industry has been continuously strengthened as the second largest industrial sector. Current circumstances are discussed, especially the need for increased innovation, the impacts of nanotechnology, biotechnology and information technologies. Some misconceptions on the Brazilian chemical industry are criticized and recent improvements are described, including those related to environmental protection, to conclude that its prospects are very good, considering both the availability of basic raw materials (oil, natural gas, agribusiness products and minerals), the growing demand and increased competitiveness.

A importância das revistas Química Nova e Journal of the Brazilian Chemical Society no crescimento da área de química no Brasil

Quimica Nova and the Journal of the Brazilian Chemical Society are two examples of successful initiatives taken by the Brazilian Chemical Society (SBQ - Sociedade Brasileira de Química), and may serve as models for the scientific societies of developing countries. Pillars of the SBQ, these two periodicals are undeniable demonstrations that idealism, utopia and dignity are the essential ingredients for transforming dreams into reality. Few believed that the Brazilian chemical community would one day have, as it does today, two scientific research periodicals indexed in the principal international data banks.