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Basic Principles of XAS and XPS

Author: Emerson Schwingel Ribeiro; Maria Suzana P. Francisco; José Eduardo Gonçalves; Yoshitaka Gushikem
February 2003

Abstract
The basic principles of the X-ray absorption and photoelectronic spectroscopy (XAS and XPS), the equipment associated with these techniques and the methods employed for data processing are introduced. Emphasis is given to studies of electronic and structural properties of inorganic materials by describing some examples found in the literature. These techniques provide different information. The [...]


Fundamental Concepts in Spectroscopy

Author: Adalberto B. M. S. Bassi
September 2001

Abstract
The effects resulting from the interaction of electromagnetic radiation with matter provide evidence for microscopic behavior. These observations lead us to propose models that enable understanding or predicting the properties of the material studied. Usually these models are associated with principles and concepts related to quantum mechanics. This topic will present the basic concepts necessary [...]


Capillary Electrophoresis

Author: Sonia Claudia do Nascimento de Queiroz; Isabel Cristina Sales Fontes Jardim
August 2001

Abstract
The phenomenon known as electrophoresis is defined as the migration of electrically charged species, which occurs when they are dissolved or suspended in an electrolyte, through which an electric current is applied. This separation technique was developed by the chemist Arne Tiselius for the study of proteins in serum and for this work he won [...]


Iodometric Determinations

Author: João Carlos de Andrade
February 2001

Abstract
Volumetric methods using oxidation and reduction reactions depend on the potential of half-reactions involved but, beyond favorable potential conditions, the oxidizing and reducing agents must be stable in solution and the substance to be determined should have a stable oxidation state, defined before the titration is started. Iodometry is an indirect volumetric method, where an [...]


Ionic Conductance and Solid Electrolytes

Author: Heloise de Oliveira Pastore
February 2001

Abstract
This text aims to show that conductivity is not a phenomenon exclusively electrical or electronic. Other charged particles, ions, can generate conduction when moving in a solid reticulum, obeying very specific structural conditions.
Keywords
electrolytes, ionic crystals, crystalline reticulum, conductors, semiconductors, insulators
Author
Heloise de Oliveira Pastore
Universidade Estadual de Campinas, Instituto de Química
Translated by
João C. de Andrade
Revised by
Carol C. [...]


Gas Chromatography: A Course in Slides

Author: Fábio Augusto
July 2000

Abstract
The separation and analysis of a mixture of volatile substances can be made through Gas Chromatography (GC). The use of this technique requires some care, among them the choice of correct stationary phase (SP) and mobile phase (MP). The temperature must be controlled, to secure the reproducibility of the analysis. These and other critical points [...]


The Linear Range of a Calibration Curve

Author: Fábio Augusto; João Carlos de Andrade; Rogério Custodio
March 2000

Abstract
Linear systems are extremely useful in the representation of experimental data and this type of calibration curve is the best known. In these cases, deviations from linearity are usually attributed to chemical and physical effects that were not initially taken into account and complicate the mathematical analysis of the data. The numerical techniques used to [...]


Law for the Processes of Absorption of Radiation

Author: Rogério Custodio; Lauro T. Kubota; João Carlos de Andrade

Abstract
Electromagnetic radiation absorbed by a sample may reveal some of its characteristics. Beer’s law establishes a linear relationship between absorbance and sample concentration. Therefore, it is possible to determine sample concentration through a calibration curve (absorbance versus concentration).
Keywords
Beer- Lambert law, Beer’s law, transmittance, absorbance, intensity of radiation, monochromatic radiation, UV-Vis, spectrometer, calibration, concentration
Authors
Rogério Custodio
Lauro T. [...]


Supersaturated Solution

Author: Maria Domitila de Menezes; Maria João M. Curto
November 1998

Abstract
The described experiment, focused on students at the high school level, aims to explore physical chemistry concepts by observing the behavior of a supersaturated solution of sodium acetate.
Keywords
solution, supersaturated solution, crystallization, exothermic reaction, teaching.
Authors
Maria Domitila de Menezes
Escola Superior de Educação de Lisboa – Portugal
Maria João M. Curto
INETI – Portugal
Translated by
João C. de Andrade
Revised by
Carol H. [...]