Estudo termogravimétrico e calorimétrico da algaroba

Humidity and ash content of powder and bran of algaroba pods are important quality parameters for biological control during storage. The studies of humidity and ash content were carried out conventional and thermogravimetric methods. Different values were obtained by the various methods. The thermogravimetric method was faster and required less sample for the humidity and ash analyses of the powder and bran of algaroba pods. The differential scanning calorimetry curves of the powder and bran of algaroba pods, dryed at 55 ºC, showed two peaks, one corresponding to the gelatinization of starch and the other to the vaporization of water. The samples dryed at 65, 75, 85, 95 and 105 ºC showed one peak, corresponding to the vaporization of water.

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.

Análise química de sais de cobre fabricados entre 1877 e 1995

Samples of copper compounds covering all of the XXth century and the end of the XIXth century were submitted to classical and instrumental quantitative analysis. The amount of impurities greatly decreased with time, reaching a constant level since the 1960's. The gravimetric method was suitable for the determination of copper although other procedures also gave good or reasonable results. However, for metal contaminants, atomic absorption spectrometry was the best choice because of its lower detection limits, being able to determine several elements in the oldest samples. Ion chromatography detected several anions in copper salts manufactured before the 1950's. An increasing quality of raw materials and a better sensitivity of analytical methods led to quality improvement of copper compounds with time.

Diagramas de Ellingham e de Van't Hoff: algumas considerações

The main subject of this article is to show the parallelism betwen the Ellingham and Van't Hoff diagrams. The first one is a graphic representation of the changes in the standard Gibbs free energy (deltarGtheta) as a function of T and was introduced by Ellingham in 1944, in order to study metallurgic processes involving oxides and sulphides. On the other hand, the Van't Hoff diagram is a representation of the function ln K versus (1/T). The equivalence between both diagrams is easily demonstrated, making simple mathematical manipulations. In order to show the parallelism between both diagrams, they are presented briefly and two examples are discussed. The comparison of the both diagrams surely will be helpful to students and teachers in their learning and teaching activities, and will certainly enrich important aspects of chemical thermodynamics.

Refletindo sobre o caso celobar®

By mid 2003, the Brazilian people accompanied astonished, in the press, the news about the death of more than 20 persons due to ingestion of a pharmaceutical product containing a suspension of barium sulfate (Celobar®) commonly used as a radiological contrast. Analysis of the product indicated the presence of barium carbonate (about 13% weight/weight) which reacts easily with the hydrochloric acid in the stomach liberating barium ions, a severe poison. In this article, we briefly discuss the possible economic, personal and technical causes that led to this disaster.

”Se olin näin, se ei ollut näin, kaikki on niin kuin sanomme sen olleen” – Postmoderni uudelleenkirjoitus historian ja fiktion suhteiden problematisoijana José Saramagon romaanissa Jeesuksen Kristuksen evankeliumi

Portugalilaisen Nobel-kirjailija José Saramagon romaani Jeesuksen Kristuksen evankeliumi (O Evangelho segundo Jesus Cristo, 1991) herätti ilmestyessään niin suuren kohun, että Saramago muutti pois synnyinmaastaan Portugalista. Teoksen saama kiihkeä vastustus johtui lähinnä sen aiheesta ja kriittisestä sisällöstä; Jeesuksen Kristuksen evankeliumi on postmoderni, kriittinen Raamatun evankeliumien uudelleenkirjoitus. Romaani kertoo kokonaisuudessaan uudestaan kanonisista evankeliumeista tutun Jeesuksen tarinan, mutta antaa useille Jeesuksen elämän vaiheille, sanoille ja teoille täysin päinvastaisen tulkinnan kuin kristinuskon perinteisessä tulkintatraditiossa. Pro gradu -työssäni tutkin paitsi sitä, miten Jeesuksen Kristuksen evankeliumi eroaa Raamatun evankeliumeista, ennen kaikkea sitä, miksi Saramagon romaani kertoo evankeliumeista tutun tarinan uudestaan. Tutkimukseni pääasiallisena teoreettisena viitekehyksenä käytän Linda Hutcheonin teoriaa historiografisesta metafiktiosta ja postmodernista taiteesta. Hutcheon kutsuu postmoderneja historiallisia aiheita käsitteleviä kaunokirjallisia teoksia historiografisiksi metafiktioiksi. Historiografinen metafiktio on kriittistä, poliittista, ironista, parodista, paradoksaalista ja intertekstuaalista. Historiografisessa metafiktiossa pääpaino ei ole menneisyyden kuvaamisessa, vaan menneisyyden kuvaamiseen liittyvissä kysymyksissä ja ongelmissa. Historiografinen metafiktio osoittaa, että menneisyyteen ei ole suoraa pääsyä eikä sitä voi kuvata ”sellaisenaan”. Menneisyyden voi tavoittaa ainoastaan aiempien representaatioiden kautta. Hutcheonin mukaan kaikki representaatiot ovat subjektiivisia, ja sen vuoksi ne pitävät aina sisällään myös tietyn ideologian. Tutkimuksessani päädyn siihen, että Saramagon kanonisten evankeliumien postmodernin uudelleentulkinnan tarkoitus on historiografisen metafiktion tapaan problematisoida historian(kirjoituksen) ja fiktion suhteet. Historian ja fiktion suhteet problematisoidessaan Jeesuksen Kristuksen evankeliumi kommentoi kanonisia evankeliumeja, moderneja Jeesus-romaaneja ja näiden perinteisiä tulkintatraditioita, sekä ilmentää postmodernille filosofialle ominaisia ajattelunvirtauksia. Saramagon kanonisten evankeliumien uudelleenkirjoitus kyseenalaistaa niin kanonisten evankeliumien kuin Jeesus-romaanien tulkintaperinteessä tyypillisen ajatuksen historiallisen totuuden olemassaolosta ja kiistää menneisyyden objektiivisen kuvauksen mahdollisuuden. Jeesuksen Kristuksen evankeliumi osoittaa historiankirjoituksen fiktiivisyyden, mutta nostaa toisaalta esiin ajatuksen fiktion mahdollisuuksista kuvata tekstin ulkopuolista todellisuutta.

Determinação experimental dos raios cristalográficos dos íons sódio e cloreto

This experiment, where very common materials and equipments are used, conducts to good and interesting results related to the ionic radii of sodium and chloride ions. It also offers an excellent opportunity to discuss the crystalline arrangement of solids and to apply simple mathematical tools for calculations. Other important concepts such as density, solubility and saturated solution are also used. The simplicity of the experiment creates an excellent opportunity for reasoning with the students about the technique.

Perfil espacial e temporal de poluentes nas águas da represa municipal de São José do Rio Preto, São Paulo, Brasil

In this manuscript, seasonal and spatial trends of water collected from two sampling places in the Preto River in the Turvo-Grande watershed were evaluated. Water samples were collected during June/07 to July/08 and parameters sulphate, total organic carbon, ammonia, conductivity, dissolved oxygen, temperature, dissolved total solids and nitrate were quantified. Seasonal trend indicated sanitary effluents as a point source of contamination in both sampling points. Vertical trends demonstrated that the Municipal Dam was not stratified and received a diffuse source of pollutants from flooding and agriculture runoffs. It was also verified that there is relatively fast ammonia consumption kinetics having a half-life time of 1.43 h which can explain the low ammonia concentrations found in these aquatic bodies.

Le Cultivateur (Paris. 1829)

Variante(s) de titre : Le Cultivateur, journal des progrès agricoles

Caracterização do material particulado fino e grosso e composição da fração inorgânica solúvel em água em São José dos Campos (SP)

Air samples of fine (PM2,5) and coarse (PM2,5-10) particulate matter were collected in São José dos Campos from February 2004 to February 2005. Average PM10 mass concentrations was 31.2 ± 14.0 μg m-3, half of which belonging to the PM2.5 fraction. Ammonium and SO4(2-) were predominantly found in the fine fraction. Average (NH4)2SO4 concentration was estimated to be about 2.9 μg m-3. Chloride, Na+ and NO3- were mostly associated with PM2,5-10. Chloride deficits with respect to sea-salt Cl/Na ratio were found in both size fractions.

Montagem de uma disciplina experimental: contribuição para a química geral

The purpose of this paper is to present a classification criterion for general chemistry experiments departing from a survey of 35 years of the experimental general chemistry discipline at the Chemistry Institute - UNICAMP. It is shown that by considering the most remarkable characteristics of an experiment and classifying it under Conceptual, Fundamental, Methodological or Quantitative criterion, teachers could better develop the discipline plan and prevent a subject superposition. Taking into account the system Fe3+/SCN- , the article also exemplify how is possible to modify an experimental approach and to conceive other procedures with different didactic purposes.

Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties

Silver containing heavy metal oxide glasses and glass ceramics of the system WO3-SbPO4-PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment.

Inhalable particulate matter characterization in a medium-sized urban region in Brazil (São José dos Campos Town) - Part I: Morphology

In this study, the concentration and morphological characteristics of inhalable particulate material (PM10) were evaluated and associated with climatic conditions. The mean annual concentration was 11.0 µg m−3, varying between 0,647 µg m−3 and 36.8 µg m−3. Wind speed has a higher influence on PM10 dispersion, but direction was associated with particle source. During the wet period, wind speed is the main dispersion factor, while speed and direction both are important during the dry period. Based on the morphological characteristics, it is concluded that biogenic particles prevail during the rainy season and terrigenous particles during the dry period, depending on the wind direction and intensity.

THOMÉ RODRIGUES SOBRAL (1759-1829) E A VIRTUDE FEBRÍFUGA DE UM GRANDE NÚMERO DE QUINAS

AbstractIn the beginning of the 19th century, Portugal received from Brazil several barks that were used as cure for fevers for the purpose of chemical analysis. These analyses were intended to determine the principle compositional components responsible for the febrifuge power of these barks. At the University of Coimbra, the samples were analyzed under the supervision of Thomé Rodrigues Sobral, the Director of the university's Chemical Laboratory. In the interpretation of the obtained results, Sobral put forward his own ideas about the febrifuge principles of the analyzed barks in relation to their chemical composition. Here, we refer to both Rodrigues Sobral's reported results and his ideas about the febrifuge principle.