Química Nova, Volume: 31, Issue: 1, Published: 2008
  • Editorial

    Torresi, Susana I. Córdoba de; Pardini, Vera L.; Ferreira, Vitor F.
  • Development and validation of a method of analysis of glyphosate in soy grains Artigo

    Abreu, Adley Bergson Gonçalves de; Matta, Marcia Helena de Rizzo da; Montagner, Émerson

    Abstract in English:

    The main objective of this work is to develop an efficient procedure to determine glyphosate in soybean grains. The cleanup of the aqueous extracts was done in two steps, beginning with liquid-liquid partitioning and then solid-phase extraction with anion exchange resin. After derivatization with a mixture of trifluoroacetic anhydride (TFAA) and trifluoroethanol (TFE), quantification was done by gas chromatography coupled to mass spectrometry. The mean recovery and RSD of the spiked samples were, respectively, 80.5% and 3.1% at level 0.200 mg kg-1, 93.3% and 18.7% at level 0.500 mg kg-1 and 92% and 3.5% at level 1.000 mg kg-1. The method was linear in the working range (correlation coefficient = 0.9965).
  • Assessment of metallic element contamination in sediments from the Santos - São Vicente Estuarine System Artigo

    Hortellani, Marcos Antonio; Sarkis, Jorge E. S.; Abessa, Denis M. S.; Sousa, Eduinetty C. P. M.

    Abstract in English:

    Three approaches were applied to evaluate metal contamination in 41 sediment samples from the Santos - São Vicente Estuarine System: normalization to Al, statistical analysis and sediment quality guidelines (SQGs). The results showed increases in the concentrations of Zn, Ni, Pb, Cd, Cr and Hg, which seemed to be associated with human activities. The levels of Al, Fe and Co probably were associated with crustal material or natural weathering processes. About 45% of the samples presented concentrations exceeding TEL-ERL, levels occasionally associated with adverse biological effects. Four of these samples presented concentrations above PEL-ERM, levels frequently associated with adverse biological effects.
  • Chemical constituents from Tabernaemontana catharinensis root bark: a brief NMR review of indole alkaloids and in vitro cytotoxicity

    Pereira, Paulo Sérgio; França, Suzelei de Castro; Oliveira, Paulo Vinicius Anderson de; Breves, Camila Moniz de Souza; Pereira, Sarazete Izidia Vaz; Sampaio, Suely Vilela; Nomizo, Auro; Dias, Diones Aparecida

    Abstract in English:

    This work describes the isolation and structural determination of pharmacological compounds present in the bark of roots of Tabernaemontana catharinensis (Apocynaceae). Among the 27 substances detected 12 were identified as terpenoid-indole alkaloids, 2 steroids and 13 pentacyclic triterpenes. Structures were outlined based on HMQC, COSY, DEPT, 13C, and ¹H NMR data and MS. Spectral data of indole alkaloids were reviewed. An in vitro screening of the extracts and isolated compounds was carried out. Compounds ibogamine (5), 3-oxo-coronaridine (9) and 12-methoxy-4-methylvoachalotine (MMV) demonstrated effective cytotoxicity towards SKBR-3 breast adenocarcinoma and C-8161 human melanoma tumor cell lines.
  • Evaluation of the influence of a coal plant operation on metal and as concentrations in the soil of Figueira, PR-Brazil Artigo

    Flues, Marlene; Sato, Ivone Mulako; Cotrim, Marycel Babosa; Figueiredo Filho, Paulo Miranda; Camargo, Iara Maria Carneiro

    Abstract in English:

    The aim of this work is to study metal and As concentrations in soil due to ash deposition from a coal plant at Figueira (PR), evaluating the macroelement (Al, Ca, Fe, Mg, Mn, Ti, V) and microelement (As, Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn) concentrations in the soil around the coal plant. The plant operation caused a slight increase in the majority of the metal concentrations in the top soil close to the plant (up to 1 km) in the wind direction (NW). The elements As, Cd, Mo, Pb and Zn are considered likely soil pollutants, and As is considered the only critical element.
  • Calculation of the difference between the actual and theoretical ECN 42 triacylglyceride content to detect adulteration in olive oil samples commercialized in Brazil Artigo

    Aued-Pimentel, Sabria; Takemoto, Emy; Kumagai, Edna Emy; Cano, Cristiane Bonaldi

    Abstract in English:

    The difference between the actual ECN 42 triacylglyceride content in vegetable oils, obtained by HPLC analysis, and the theoretical value calculated from the fatty acid composition was applied to detect the addition of seed oils with high contents of linoleic acid to olive oils commercialized in Brazil. The results indicate that samples analyzed were probably adulterated with low commercial value seed oils, rich in linoleic acid, like soybean, sunflower or corn.
  • Comparative performance of Candida rugosa lipase immobilized on polysiloxane polyvinyl alcohol hybrid support using different methodologies Artigo

    Paula, Ariela V.; Moreira, Ana B. R.; Braga, Luciana P.; Castro, Heizir F. de; Bruno, Laura M.

    Abstract in English:

    The efficiency for immobilizing microbial Candida rugosa lipase on a hybrid matrix of polysiloxane polyvinyl alcohol, by adsorption, covalent coupling and encapsulation was compared. The activities of immobilized derivatives were evaluated using p-nitrophenylpalmitate (hydrolysis) and butyric acid and butanol (esterification) as substrates. Operational stability and storage tests were also performed. Among the procedures tested, the proposed matrix was efficient for immobilizing C. rugosa lipase by adsorption and covalent coupling techniques and unsuitable for encapsulation purposes. The results reveal that better catalytic properties in both aqueous and organic media were demonstrated by the covalent coupling POS-PVA immobilized lipase, including also satisfactory half-life and good storage stability.
  • Mineral and vitamin content of beef, chicken, and turkey hydrolysates mineral and vitamin content of protein hydrolysates

    Pinto e Silva, Maria Elisabeth Machado; Paton, Ive; Trigo, Marlene; von Atzingen, Maria Carolina B. C.; Kira, Carmem S.; Inomata, Emiko I.; Lamardo, Leda C. A.

    Abstract in English:

    The purpose of this study was to assess the concentration of vitamins and minerals in meat protein hydrolysates. Calcium, phosphorus and iron were analyzed by inductively coupled-plasma atomic emission spectrophotometry; vitamin C was analyzed by the reduction of cupric ions and vitamins B1 and B2 by fluorescence. Regarding minerals, the beef hydrolysate (BH) had more iron than the turkey hydrolysate (TH) and the chicken hydrolysate (CH); TH had a little more phosphorus. BH had the largest amount of vitamin C, and similar amounts of vitamins B1 and B2. The amount of these nutrients found in the hydrolysates suggests that it is possible to use them to enrich special dietary formulations.
  • Determination of diuretic drugs by thin layer chromatography and spectrophotometry Artigo

    Valladão, Dênia Mendes de Sousa; Ionashiro, Massao; Zuanon Netto, José

    Abstract in English:

    A rapid, sensitive and reliable thin-layer chromatography/spectrophotometry screening procedure was developed for quantitative determination of diuretics associated in pharmaceutical dosage forms. The chromatographic method employed microcrystalline cellulose and butanol : acetic acid : water (4:1:1) or amilic alcohol : ammonium hydroxide 25% (9:1) as mobile phases and detection by U.V. light. The drugs were extracted using a simple procedure and were quantified by U.V. spectrophotometry. Results varied from 97.5 to 102.5% and are similar to those obtained by conventional methods. This method of quantification of diuretics is promising for quality control of drugs.
  • Reversed phase HPLC determination of tamoxifen in dog plasma and its pharmaco-kinetics after a single oral dose administration

    Santana, Davi Pereira de; Braga, Rossana Maria Carvalho; Strattmman, Ruth; Albuquerque, Miracy Muniz; Bedor, Danilo César Galindo; Leal, Leila Bastos; Silva, José Alexsandro da

    Abstract in English:

    The analytical method developed to evaluate tamoxifen in dog plasma samples was precise, accurate, robust and linear in the range of 5-200 ng/mL. The limits of detection and quantification were 0.981 ng/mL and 2.97 ng/mL, respectively. Besides, the intra-day precision and accuracy variations were 8.78 and 10.16%, respectively. Tamoxifen concentrations were analyzed by combined reversed phase liquid chromatography and UV detection (lambda=280 nm). The study was conducted using an open randomized 2-period crossover balanced design with a 1-week washout period between the doses. This simple, rapid and selective method is suitable for pharmacokinetic, bioavailability and bioequivalence studies.
  • Chemical composition and biological activity of leaves and fruits of Triphasia trifolia Artigo

    Santos, Renata P. dos; Trevisan, Maria Teresa Salles; Silveira, Edilberto R.; Pessoa, Otília Deusdênia L.; Melo, Vânia Maria M.

    Abstract in English:

    The chemical composition of the essential oils from leaves and fruits of Triphasia trifolia was analyzed by GC-FID and GC-MS. The major constituents of oil obtained from leaves were sabinene (35.4%) and myrcene (34.1%), while the prevalent compounds in oil from fruits were sabinene (37.2%), beta-pinene (23.95) and gamma-terpinene (16.3%). Both oils showed moderate antimicrobial activity. The fruit decoction was also investigated leading to the isolation of the coumarins isopimpinelin, (R)-byakangelicin and (S)-mexoticin. From leaves were isolated the coumarins (R)-byakangelicin, aurapten, (S)-mexoticin, isosibiricin, isomerazin and coumurrayin and the flavonoid vitexin. All coumarins showed cholinesterase inhibition on TLC tests.
  • Flavonoids in Astragalus corniculatus

    Krasteva, Ilina; Nikolov, Stefan

    Abstract in English:

    Nine flavonoids were identified in aerial parts of Astragalus corniculatus Bieb. (Fabaceae) by liquid chromatography coupled with ionspray mass spectrometry in the tandem mode (LC/MS/MS) with negative ion detection. Vitexin, orientin and eriodictyol-7-O-glucoside are obtained for the first time in genus Astragalus L, and isorhamnetin-3-O-glucoside in the species.
  • Ionic desorption and degradation of polypyrrole films doped with dodecylsulfate induced by high energy electrons Artigo

    Arantes, Caroline; Rocco, Maria Luiza M.; Cruz, Antonio Gerson Bernardo da; Rocco, Ana Maria

    Abstract in English:

    Electron stimulated ion desorption (ESID) and degradation studies of polypyrrole doped with dodecylsulfate (PPy/DS) deposited on FTO were performed using time-of-flight mass spectrometry (TOF-MS) for ion analysis. The results suggest a strong contribution from fragments of the dodecylsulfate hydrocarbon chain to the mass spectra. In the 650-1500 eV energy range the ion yield curves show maxima at about 600, 1200 and 1400 eV, which can be related to carbon, nitrogen and oxygen-containing fragments, respectively, and interpreted in terms of the Auger Stimulated Ion Desorption (ASID) mechanism. Degradation studies indicate rapid loss of heavier hydrocarbons and an increase of bulk and substrate fragments. Some degradation profiles suggest formation of new species.
  • Chemical constituents of Licania tomentosa Benth. (Chrysobalanaceae) Artigo

    Castilho, Rachel Oliveira; Kaplan, Maria Auxiliadora Coelho

    Abstract in English:

    This paper describes the chemical constituents isolated from leaves and fruits of Licania tomentosa Benth. The plant materials were successively extracted with hexane and methanol. From the extracts the following compounds were obtained: betulinic acid; licanolide, a new triterpene lactone; oleanolic acid, lupeol; palmitoleic and hexadecanoic acid; a mixture of stigmasterol and sitosterol; and a mixture of tormentic, ursolic and betulinic acid. The structures of the natural products were identified on the basis of spectral data.
  • Cloud point extraction for the determination of copper in environmental samples by flame atomic absorption spectrometry

    Shokrollahi, Ardeshir; Ghaedi, Mehrorang; Gharaghani, Shiva; Fathi, Mohammad Reza; Soylak, Mustafa

    Abstract in English:

    A simple cloud point extraction procedure is presented for the preconcentration of copper in various samples. After complexation by 4-hydroxy-2-mercapto-6-propylpyrimidine (PTU), copper ions are quantitatively extracted into the phase rich in Triton X-114 after centrifugation. Methanol acidified with 0.5 mol L-1 HNO3 was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). Analytical parameters including concentrations for PTU, Triton X-114 and HNO3, bath temperature, centrifugation rate and time were optimized. The influences of the matrix ions on the recoveries of copper ions were investigated. The detection limits (3SDb/m, n=4) of 1.6 ng mL-1 along with enrichment factors of 30 for Cu were achieved. The proposed procedure was applied to the analysis of environmental samples.
  • Evaluation of advanced oxidation processes for remediation of contamined water with geosmin and 2-MIB Artigo

    Freitas, Adriane Martins de; Sirtori, Carla; Peralta-Zamora, Patricio G.

    Abstract in English:

    In this work, the efficiency of some homogeneous advanced oxidation processes (UVC/H2O2, Fe2+/H2O2, UVC/Fe2+/H2O2, UVA/Fe2+/H2O2, solar/Fe2+/H2O2) was investigated toward the degradation of geosmin and 2-methylisoborneol (2-MIB). The effect of relevant experimental parameters (ie. pH, Fe2+ and H2O2 concentration) was first investigated by factorial design, using camphor as a model substrate. In the geosmin and 2-MIB degradation studies the Fenton processes assisted by solar and UVA radiation offered the most promising results, mainly on account of high degradation capacity (higher than 80% at a reaction time of 60 min), high operational simplicity and low cost.
  • Determination of herbicides used in irrigated rice cultivation in the south of Santa Catarina using SPME-GC-ECD Artigo

    Costa, Léa L. F.; Sant'ana, Ernani S.; Suchara, Eliane A.; Benato, Vanira S.; Carasek, Eduardo

    Abstract in English:

    Evaluation of the pollution by the herbicides alachlor, propanil and atrazine in water samples from four rivers in the cities of Turvo and Meleiro, south of Santa Catarina State, was made using the SPME-GC-ECD method. The proposed method was optimized and validated. The correlation coefficients were higher than 0.997 and linear ranges of the analytical curves were 0.1-4; 0.1-2.5 and 0.1-5 µg L-1 for atrazine, alachlor and propanil, respectively. The herbicides were quantified by GC-ECD and identified by GC-MS. Both of the selected rivers presented contamination by at least one of the studied herbicides.
  • Chemical and physical modification of broken rice starch (Oryza sativa L.) for use in food industry Artigo

    Limberger, Valéria Maria; Silva, Leila Picolli da; Emanuelli, Tatiana; Comarela, Carine Gláucia; Patias, Luciana Dalpieve

    Abstract in English:

    The study evaluated the efficiency of chemical (phosphorylation) and physical (extrusion) modifications of the starch of broken rice. Results demonstrated a reduction in the moisture content of extruded and phosphorylated broken rice and an increase in the ash content of phosphorylated broken rice. Both phosphorylation and extrusion increased cold water binding capacity, swelling power, and solubility. Extruded and phosphorylated pastes were stable under refrigeration, but only extruded paste was stable when submitted to freezing. Phosphorylated paste had the lowest viscosity and the highest stability during heating, while the extruded one gelatinized without heating, but had higher losses during heating.
  • Butyltin speciation in sediments from Todos os Santos Bay (Bahia, Brazil) by GC-PFPD

    Felizzola, Juliana Feitosa; Wagener, Angela de Luca Rebello; Almeida, Ana Cristina; Lin, Wei Oh

    Abstract in English:

    Butyltin compounds were investigated in surface sediments from 17 stations in Todos os Santos Bay. Analytical conditions for organotin determination in marine sediments were optimized for GC with pulsed flame photometric detection. Detection limits were: 5.4 µg kg-1 for TBT; 0.2 µg kg-1 for DBT; and 2.1 µg kg-1 for MBT, using a 610-nm filter. In general, TBT concentrations were low and in the range of <DL to 15.9 µg kg-1. Only in one of the investigated stations DBT and MBT were above detection limit despite the oxic to slightly anoxic conditions in the sediments. The presence of paint particles in the sediments and degradation in the water column during resuspension events followed by removal of the more soluble DBT and MBT may explain these observations.
  • Comparative study of carbon quantification methods in soil with high Fe contents (Oxisols) Artigo

    Segnini, Aline; Santos, Larissa Macedo dos; Silva, Wilson Tadeu Lopes da; Martin-Neto, Ladislau; Borato, Carlos Eduardo; Melo, Wanderley José de; Bolonhezi, Denizart

    Abstract in English:

    Soil organic matter (SOM) plays an important role in physical, chemical and biological properties of soil. Therefore, the amount of SOM is important for soil management for sustainable agriculture. The objective of this work was to evaluate the amount of SOM in oxisols by different methods and compare them, using principal component analysis, regarding their limitations. The methods used in this work were Walkley-Black, elemental analysis, total organic carbon (TOC) and thermogravimetry. According to our results, TOC and elemental analysis were the most satisfactory methods for carbon quantification, due to their better accuracy and reproducibility.
  • A thermogravimetric analysis of the combustion of a Brazilian mineral coal

    Silva Filho, Claudionor Gomes da; Milioli, Fernando Eduardo

    Abstract in English:

    Knowledge of coal combustion kinetics is crucial for burner design. This work aims to contribute on this issue by determining the kinetics of a particular Brazilian bituminous coal. Non-isothermal thermogravimetry was applied for determining both the pre-exponential factor and the activation energy. Coal samples of 10 mg and 775 mm mean size were used in synthetic air atmospheres (21 % O2). Heating rates from 10 to 50 ºC/min were applied until the temperature reached 850 ºC, which was kept constant until burnout. The activation energy for the primary and the secondary combustion resulted, respectively, in 135.1 kJ/mol and 85.1 kJ/mol.
  • Solid sampling graphite furnace atomic absorption spectrometry: a review Revisão

    Nomura, Cassiana Seimi; Silva, Cíntia Soares da; Oliveira, Pedro Vitoriano

    Abstract in English:

    This is a review of direct analysis using solid sampling graphite furnace atomic absorption spectrometry. Greater emphasis is dedicated to sample preparation, sample homogeneity, calibration and its application to microanalysis and micro-homogeneity studies. The main advantages and some difficulties related to the applicability of this technique are discussed. A literature search on the application of solid sampling graphite furnace atomic absorption spectrometry in trace element determination in many kinds of samples, including biological, clinical, technological and environmental ones, is also presented.
  • Advanced Oxidation Process of phenolic compounds in industrial wasterwater Revisão

    Britto, Jaildes Marques; Rangel, Maria do Carmo

    Abstract in English:

    In an effort to minimize the impact on the environment, removal of pollutants, such as phenolic compounds, from the industrial wastewater has great importance nowadays because of the high toxicity and low biodegradability of these compounds. This work discusses the different methods to remove these compounds from industrial wastewater, showing their advantages and disadvantages. Advanced Oxidation Process (AOPs) are presented as a promising technology for the treatment of wastewater containing phenolic compounds. Among the AOPs, photolysis, photocatalysis and the processes based on hydrogen peroxide and on ozone are discussed with emphasis on the combined processes and the oxidation mechanisms.
  • Ultrasound applications in electrochemical systems: theoretical and experimental aspects Revisão

    Garbellini, Gustavo S.; Salazar-Banda, Giancarlo R.; Avaca, Luis A.

    Abstract in English:

    The aim of this review is to present and discuss the applications of ultrasound in electrochemical systems such as in sonoelectroanalysis and sonoelectrolysis for the electrochemical combustion of organic compounds. Initially, theoretical and experimental aspects are discussed, particularly those related to the enhancement of mass transport and the surface cleaning effects. Some results are included to illustrate alternative geometries for the experimental measurements and the working electrodes used in these systems. In the sequence, the available publications are presented and discussed to demonstrate that ultrasound combined with electrochemical techniques is a powerful set-up for the detection of analytes such as metals and/or organic compounds in hostile media and for the effective destruction of toxic organic substances. At the end, a table summarizes the results already published in the literature.
  • Isomaltulose production, a new sucrose substitute, using microbial glucosyl transferase Revisão

    Kawaguti, Haroldo Yukio; Sato, Hélia Harumi

    Abstract in English:

    Isomaltulose, a functional isomer of sucrose, is a non-cariogenic reducing disaccharide; has a low glycemic index; selectively promotes growth of beneficial bifidobacteria in the human intestinal microflora; and has greater stability than sucrose in some foods and beverages. Isomaltulose is a nutritional sugar that is digested more slowly than sucrose, and has health advantages for diabetics and nondiabetics. Immobilization techniques, especially entrapment of the cells, are widely used for conversion of sucrose into isomaltulose. Immobilization offers advantages such as minimum downstream processing, continuous operation and reusability of cells. Isomaltulose is currently considered to be a promising sugar substitute.
  • The weighty potentiality of nitrogenated basic centers in inorganic polymers and biopolymers for cation removal Revisão

    Airoldi, Claudio

    Abstract in English:

    This review reports the application of inorganic and organic polymeric materials for cation removal by using nitrogenated basic centers. The data demonstrate the importance of the desired groups when free or immobilized on natural or synthesized inorganic polymers through silanol groups. Thus, the most studied silica gel is followed by natural crysotile and talc polymers, and the synthesized mesopore silicas, talc-like, silicic acids, phosphates and phyllosilicates. The organic natural biopolymeric chitin and cellulose were chemically modified to improve the availability of the amine groups or the reactivity with desirable molecules to enlarge the content of basic centers. The cation removal takes place at the solid/liquid interface and some interactive effects have their thermodynamic data determined.
  • Laüe back-reflection method for crystallographic orientation of a martensitic Cu-Zn-Al single crystal of the monoclinic system

    Zambrano, Uíslei Carlos; Blanco, Matildes; Barelli, Nilso; Benedetti, Assis Vicente; Fernández, Javier

    Abstract in English:

    A martensitic single crystal Cu-23.95Zn-3.62(wt.%)Al alloy was obtained melting pure Cu, Zn and Al using Bridgman's method. The martensitic phase (monoclinic) can present up to 24 variants, and orienting the surface according to a certain plane is a very hard task. The single crystal was submitted to 8 tons of tension (stress) along the longitudinal direction to reduce the number of variants and facilitate the surface orientation according to the desired plane. This single crystal was oriented using the Laüe back-reflection method to give surfaces with the following oriented crystallographic planes: (010), (120) and (130). It was observed that the tension stress was applied along the [010] direction.
  • Simple system for preparation of chitosan microspheres Nota Técnica

    Dias, Francisco S.; Queiroz, Danilo C.; Nascimento, Ronaldo F.; Lima, Mario Bastos

    Abstract in English:

    This article describes the construction and optimization of an inexpensive apparatus for the production of uniform and porous chitosan microspheres. It also describes the control of the main operational parameters and strategies for the production of uniform chitosan microspheres.
  • Validation spreadsheet: a new tool for estimating the analytical figures of merit for the validation of univariate methods Nota Técnica

    Ribeiro, Fabiana Alves de Lima; Ferreira, Márcia Miguel Castro; Morano, Sandra Campilongo; Silva, Lucimara Rodrigues da; Schneider, René Peter

    Abstract in English:

    This work presents the VALIDATION SPREADSHEET, a public domain tool that can be used to evaluate the figures of merit for univariate analytical methods. A real example of BTEX determination in environmental samples is included to illustrate its use. The spreadsheet has been developed for Excel® and Open Office®, and is available on the internet at http//lqta.iqm.unicamp.br.
  • Preparation of para-cloroanilina: a simple, fast and inexpensive experiment Educação

    Bastos, Renato Saldanha; Cunha, Andréa Sousa da; Silva, Lucyane Costa da; Oliveira, Carina Cantelle Pacheco de; Rezende, Cláudia M.; Pinto, Angelo C.

    Abstract in English:

    Experiments simple, short and efficient for experimental disciplines in undergraduate courses in Chemistry are an excellent opportunity for students to consolidate the learning of theoretical concepts in classical chemical transformations. The use of a safe reagent, of low cost and easy access is the motivation for this communication, that describes the use of trichloroisocyanuric acid - a chlorinating agent used in the treatment of swimming pool water - for the chlorination of acetanilide, an intermediate in the preparation of para-chloroaniline.
  • From residue to input: building a road to clean chemistry through an educational project Educação

    Felisberto, Regina; Vieira, Lucio Olimpio; Couto, Alessandra; Schuh, Roselena; Albino, Caroline Thiessen; Libardi, Daniela Batistela; Cunha, Ana Cristina Borba da

    Abstract in English:

    The discussion among teachers, students, and technicians about the destination of residues from chemistry laboratories led to a research project whose results were incorporated into a course in its daily practices. The treatment of the residues from argentimetric practices allowed us to establish cognitive relations of technological basis and of those related to the rising of the level of awareness about environmental aspects and social responsibility of chemistry professionals. The techniques and the results, from the economic point of view, namely that of value aggregation (metallic silver) and the conversion of the residue into input (potassium chromate solution) are shown.
  • The polymorphs of calcium carbonate: an easy synthesis of aragonite Educação

    Bessler, Karl E.; Rodrigues, Laécio C.

    Abstract in English:

    Aragonite is a metastable polymorph of calcium carbonate. The calcareous exoskeletons of some organisms like corals or molluscs consist essentially of aragonite. The questions of how, and why these organisms prefer the thermodynamically unstable aragonite for the construction of their hard shells are discussed. The importance of the biomineralization process for the development of new materials is outlined. In the experimental part, a very simple synthesis of polycrystalline aragonite is performed, using carbonated mineral water available at the market. The synthesized aragonite is easily identified by its infrared spectrum.
  • Humphry Davy and the colors of the ancients Assuntos Gerais

    Beltran, Maria Helena Roxo

    Abstract in English:

    This article examines ideas held by Humphry Davy (1778-1829) about permanence, progress, experiments and practical application regarding chemistry. Furthermore, it relates ideas held in his "Some experiments and observations on the colours used in painting by the Ancients" (1815), with those maintained in Elements of Chemical Philosophy (1812), as well as to cogitations from his last years, disclosed in Consolations in travel (1830). Lastly, it brings up evidence that H. Davy's study about the colors of the ancients influenced his proposals for Chemical Philosophy and the science of his age.
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