Experimentos didáticos em química analítica envolvendo separação de fases e pré-concentração

The aim of this work was to propose two different didactic experiments, which can be used in practical classes of analytical chemistry courses. More flexible experiments related to the theme, giving some options to the instructor are proposed. In this way, the Experiment 1 was divided in two parts. In the first one, the visualization of two distinct phases separation is emphasized: the rich and the poor phases in surfactant. In the second part, the metal pre-concentration (Co as example) is emphasized. The Experiment 2 has three different parts. In the first one, the complex formation is pointed out, in the second one, the pH influence is shown and in the last one, the influence of the complexation time is demonstrated.

História da química e da geologia: Joseph Black e James Hutton como referências para educação em ciências

The second half of eighteenth century is marked by the advancement of chemistry and geology. The first science acquired the law of conservation of mass and this science represented a important support to geology and mineralogy. We say that both became modern science that time. Our aim is to show up some interrelations between history of chemistry and history of geology by means of the study of Joseph Black's and James Hutton's works. We defend that it is positive to science education to understand and approach the relations among different and disciplinary areas of science.

Formação e trabalho de mestres e doutores em química titulados no Brasil

This article reports questions related to the training and jobs of chemistry graduates from Brazilian universities. It is focussed on academic and career paths and on relations between knowledge and work. The main questions addressed in this study were: what have been the paths since undergraduate education? what were graduates doing before their enrolment in master and doctoral programs? Which were their motivations for this? Where do graduates work now? How do they appraise some aspects of their graduate education? Did the degree enlarge their job opportunities and improve work quality? How much do they earn?

Felisa Jordán, la madre de Estanislao Zeballos. Prácticas asociativas, espacio público y proyección femenina en Argentina (1870-1880)

La reconstrucción de la historia de la madre del conocido Estanislao Severo Zeballos es el objetivo de este artículo que se centra en la búsqueda del rol ejercido por Felisa Jordán durante la organización del Estado-Nación de la República Argentina. Zeballos divulgó algunos datos de su vida privada, como su parentesco con los Urquiza y los Ruiz Moreno, o su condición de propietario de 351.562 hectáreas en el Chaco Boreal gracias a la mediación que practicó en el transcurso de la firma del tratado boliviano-paraguayo que fijó la línea de statu-quo de 1907. Pero el relato más creativo del rosarino Estanislao fue la gestión de su madre Felisa Jordán de Zeballos en el marco del ámbito asociativo de la ciudad de Rosario. Para describir esta llamativa vinculación entre Zeballos y su madre Felisa Jordán me he centrado en dos fuentes documentales singulares que nos permiten abordar las prácticas asociativas, los espacios públicos y la proyección femenina en Argentina entre 1869 y 1872. En primer lugar en los documentos privados de las mujeres de élite de la Ciudad de Rosario, en particular las actas y la correspondencia de la asociación benéfica Damas de Caridad. Esta documentación signó durante años mi investigación sobre el Asilo de Huérfanos y Expósitos cuyo nombre fue modificado por Hogar del Huérfano por el peronismo, una institución que hoy día se encuentra en un futuro incierto. La secretaria de aquella asociación femenina fue la llamativa Felisa Jordán, la viuda del militar Estanislao Zeballos, que colaboraba activamente con la presidenta de la asociación Damas de Caridad, María de los Ángeles Rodríguez de Rosas, y con la tesorera Blanca Musch de Villegas en cuyo domicilio se reunieron por primera vez para formar la entidad en el año 1869, es decir, en plena Guerra de la Triple Alianza. La documentación de las hoy llamadas Damas de Protección al Huérfano se conserva en el archivo del Hogar del Huérfano, otrora denominado Hogar de Huérfanos y Expósitos, y hace referencia a aspectos de la vida cotidiana de la entidad, de la asociación femenina y de sus socias.

Recomendações para calibração em química analítica: parte I. Fundamentos e calibração com um componente (calibração univariada)

This paper is a translation from IUPAC nomenclature document by K. Danzer and L. A. Currie (Pure Appl. Chem., 1998, 70(4), 993-1014). Its goal is to establish an uniform and meaningful approach to terminology (in Portuguese), notation, and formulation for calibation in analytical chemistry. In this first part, general fundamentals of calibration are presented, namely for both relationships of qualitative and quantitative variables (relations between variables characterizing certain types analytes of the measured function on the other hand and between variables characterizing the amount or concentration of the chemical species and the intensities of the measured signals, on the other hand). On this basis, the fundamentals of the common single component calibration (Univariate Calibration) which models the relationship y = f(x) between the signal intensities y and the amounts or concentrations x of the analyte under given conditions are represented. Additional papers will be prepared dealing with extensive relationships between several intensities and analyte contents, namely with multivariate calibrations and with optimization and experimental design.

Química de sistemas supramoleculares constituídos por porfirinas e complexos metálicos

Supramolecular chemistry is expected to keep a high developing pace in the next years, giving support to the advancement of molecular devices and nanotechnology. In this sense, porphyrins and their analogues should play a significant role as a consequence of their catalytic, electrocatalytic, photochemical and photoelectrochemical properties. In this review we focused on our own strategy based on coordination chemistry for the design and build-up of supermolecules and supramolecular structures constituted by polynuclear porphyrins and metalloporphyrins. Included are also their properties and potential applications.

Química organometálica de superfície aplicada à preparação de catalisadores heterogêneos bem definidos

The study of the reactions of organometallic complexes with the surfaces of inorganic oxides, zeolites and metals constitutes the basis of Surface Organometallic Chemistry (SOMC). The basic rules of organometallic chemistry are often valid when applied to surfaces and well-defined surface organometallic complexes can be obtained. These complexes can be used as heterogeneous catalysts or, by controlled reactions, can be transformed in other species useful for a given catalytic reaction. In some cases, these catalysts exhibit higher activity and/or selectivity than their analogous molecular complexes.

Um experimento com propostas múltiplas para um laboratório de química geral

This article suggests a sequence of experiments on the preparation, analysis and some photochemical aspects of potassium tris (oxalato) ferrate(III) trihydrate. The sequence of experiments could be carried out in four or five 4-hour laboratory periods. The new part of this article is related to the kinetics studies involving the ambient illumination as well as the use of the cellophane paper of different colors as light filters. The aspects such as quantum yield, light absorption and photochemical reactions are explored in order to illustrate the relationships between the exposure time, light intensity and wavelength range on the photochemical reactions.

A geração química de vapor em espectrometria atômica

The historical development of atomic spectrometry techniques based on chemical vapor generation by both batch and flow injection sampling formats is presented. Detection via atomic absorption spectrometry (AAS), microwave induced plasma optical emission spectrometry (MIP-OES), inductively coupled plasma optical emission spectrometry (ICP-OES) , inductively coupled plasma mass spectrometry (ICP-MS) and furnace atomic nonthermal excitation spectrometry (FANES) are considered. Hydride generation is separately considered in contrast to other methods of generation of volatile derivatives. Hg ¾ CVAAS (cold vapor atomic absorption spectrometry) is not considered here. The current state-of-the-art, including extension, advantages and limitations of this approach is discussed.

Licenciatura em Química da UFC: perfil sócio-econômico, evasão e desempenho dos alunos

This paper describes the studies of the performance and the efficiency of the Degree in Chemistry (nocturne) course at the UFC. The study embraces the period of its foundation (1995) until the current days. In general, the course has enhanced its efficiency, with an evident improvement presented by the students, which are more confident with strong indicative of better social prestige.

A química do estanho no século 18, ou como uma consulta se transformou num projeto de pesquisa

An ominous suspicion arose in France in the second half of the 18th century, that household tin objects might be contaminated with arsenic. Charged with the task of studying and deciding the question, the chemists Pierre Bayen and Louis Charlard set up a comprehensive research project, which resulted in a book describing the whole enterprise. It is very gratifying to analyse this work today, for the many lights it sheds on the way chemistry was practised and reasoned at the time, and for the whiff of modernity we are presented with.

A Química Ambiental no Brasil

Defining environmental chemistry is a not an easy task because it encompasses many different topics. According to Stanley E. Manahan, author of a classical textbook of Environmental Chemistry, this branch could be defined as the one centered in the study of the sources, transport, effects and fates of chemical species in the water, soil, and air environments, as well as the influence of human activity upon these processes. More recently, new knowledge emerged from the Environmental Toxicology allowed to go even deeper in the meaning of 'effects' and 'fates' of a continuous growing number of organic and inorganic species disposed in water bodies, soils and atmosphere. Toxicity tests became an important tool to evaluate the environmental impact of such species to a great number of organisms, thus allowing to set quality criteria for drinking water, sediments and biota. The state of art shows that environmental chemistry is a multi-inter disciplinary science by nature; therefore, it needs more than a limited, unique-approach and non-oriented set of data to understand the nature of natural processes. Taking all these aspects into consideration, one can say that Environmental Chemistry in Brazil is now a well established area of research within the classical areas of the Chemistry, with a large number of emerging groups as well research groups with worldwide recognition.

A pesquisa em ensino de química no Brasil: conquistas e perspectivas

This article summarizes the main achievements of the Brazilian research in chemistry education in these 25 years of existence of the Brazilian Chemical Society and raises some prospective questions for the field. Six main events are described as the responsible ones for the development of research in chemistry teaching in Brazil. Valuable contributions of Brazilian researches are discussed and related with international trends in science education. Some perspectives for improving research in chemistry teaching in Brazil are also presented.