Acid Base Indicators
Mostrando 1-12 de 13 artigos, teses e dissertações.
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1. Sulfonated Styrene-Acrylic Acid Copolymers with pH-Indicator Property
In this study, a polymer pH-indicator was synthesized by sulfonation of poly(styrene-co-acrylic acid) with concentrated sulfuric acid. The synthesized polymer pH-indicator exhibited pH-responsive color changes in aqueous solutions, being purple in alkaline medium (pH < 4), whereas yellow in acidic medium (pH > 9). The sulfonation process extent and polymer c
J. Braz. Chem. Soc.. Publicado em: 16/09/2019
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2. Influence of the anodizing process variables on the acidic properties of anodic alumina films
Abstract In the present work, the effect of the different variables involved in the process of aluminum anodizing on the total surface acidity of the samples obtained was studied. Aluminum foils were treated by the electro-chemical process of anodic anodizing within the following variable ranges: concentration = 1.5-2.5 M; temperature = 303-323 K; voltage =
Braz. J. Chem. Eng.. Publicado em: 2017-10
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3. Antocianinas em extratos vegetais: aplicação em titulação ácido-base e identificação via cromatografia líquida/espectrometria de massas
Anthocyanins extracted from picao, quaresmeira, petunia, flamboyant, purple ipe, lobeira, pata de vaca, jaboticaba, purple cabbage and jambul were evaluated as natural acid-base indicators. Anthocyanins in extracts were identified using HPLC/MS. Clear, rapid change in color at final-point titration was observed for extracts but only picao showed strong chang
Quím. Nova. Publicado em: 2012
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4. Aplicação de um corante tiazolilazo como indicador ácido-base e determinação das suas constantes de ionização ácida
The pKa values of the 6-[2´-(6´-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD) have been determined at 25 °C, in 0.10 mol L-1 NaCl medium by spectrophotometric method. The SQUAD computer program was used to process experimental data in pH range 1.78 - 11.54 and 290 - 720 nm. The pKa values obtained were 4.60 ± 0.04 and 9.48
Química Nova. Publicado em: 2009
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5. Desenvolvimento de mÃtodos analÃticos rÃpidos e de baixo custo utilizando ciclodextrinas para o controle de qualidade de fÃrmacos
O Ãcido desoxicÃlico (DCA) e o Ãcido ursodesoxicÃlico (UDCA) sÃo Ãcidos biliares com inÃmeras aplicaÃÃes farmacÃuticas, no entanto, as metodologias empregadas para determinaÃÃo de suas concentraÃÃes sÃo demoradas e onerosas. Neste trabalho foram usadas as ciclodextrinas, oligossacarÃdeos cÃclicos, que tÃm a capacidade de formar complexos de
Publicado em: 2009
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6. Titulações espectrofotométricas de sistemas ácido-base utilizando extrato de flores contendo antocianinas
Considering the attraction of the students' attention by the changes in the colors of vegetable crude extracts caused by the variation of the pH of the medium, the use of these different colors in order to demonstrate principles of spectrophotometric acid-base titrations using the crude extracts as indicators is proposed. The experimental setup consisted of
Química Nova. Publicado em: 2007-08
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7. O pKa de indicadores ácido-base e os efeitos coloidais
An experiment is proposed that can be included in undergraduate courses of chemistry. The subject is the acidity of organic compounds, which are employed as pH indicators, particularly in acid-base titrations. The indicators used are methyl orange, bromophenol blue and bromocresol green in aqueous medium. The influence of colloidal systems on the equilibrium
Química Nova. Publicado em: 2006-06
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8. Aplicação de extratos brutos de flores de quaresmeira e azaléia e da casca de feijão preto em volumetria ácido-base. Um experimento para cursos de análise quantitativa
Crude extract of Tibouchina granulosa, Rhododendron simsii and Phaseolus vulgaris L. were prepared and used as alternative indicators in quantitative analysis teaching in standardization of NaOH solutions and in the determination of acetic acid contents in vinegar. Effect of using such natural extracts as indicators was very attractive to the students and th
Química Nova. Publicado em: 2001-06
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9. Avaliação da capacidade tamponante - um experimento participativo
The aim of this work is to show an experiment from which students can learn some of the main characteristics of buffer solutions. A mixture of some acid-base indicators, named as Yamada's indicator, can be used to estimate pH values in an acid-base titration of a buffer, with good approximation. In the experiment it is also possible to verify the relationshi
Química Nova. Publicado em: 2000-06
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10. Desenvolvimento de um espectrofotometro multicanal para analise multivariada em sistema de fluxo
In this work was searched the application of chemometric methods for analysis of multiway data, obtained in flow systems that use a concentration gradient generated by dispersion, and multichannel spectrophotometric detection by photodiode array. These techniques can turn analysis even in presence of interference and with a reduced number of standards. It wa
Publicado em: 1997
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11. Decoupling of photo- and proton cycle in the Asp85-->Glu mutant of bacteriorhodopsin.
Surface bound pH indicators were applied to study the proton transfer reactions in the mutant Asp85-->Glu of bacteriorhodopsin in the native membrane. The amino acid replacement induces a drastic acceleration of the overall rise of the M intermediate. Instead of following this acceleration, proton ejection to the extracellular membrane surface is not only tw
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12. Increased expression of the bifunctional protein PrlF suppresses overproduction lethality associated with exported beta-galactosidase hybrid proteins in Escherichia coli.
We have cloned and determined the nucleotide sequence of the prlF gene. An open reading frame predicting a 111-amino-acid protein (Mr 12,351) with an acidic carboxy terminus was identified. The DNA sequence preceding this open reading frame revealed a putative promoter and a ribosome-binding site. The nucleotide sequence of the prlF1 mutation revealed a 7-ba