A green potentiometric method for the determination of the iodine number of biodiesel

AbstractIn this paper a green potentiometric method is proposed for the determination of the iodine number of biodiesel. The solvent used is simply a water–ethanol mixture (1:1v/v) and the reagent is iodine. The analytical procedure can be performed even without a laboratory hood as no iodine vapors are released if the method is done as indicated. The analytical results obtained with this procedure were compared with those from Wijs’ method. In order to strictly compare instrumental procedures potentiometry was also applied to the Wijs’ procedure. Also for comparison purposes a green visual method was applied. Statistical comparison of the four methods, through the paired Student’s t test and the F test of Snedecor showed excellent agreement among all of them

The use of the liquid from cashew nut shells as an antioxidant in biodiesel

The influence of cashew nutshell liquid (CNSL) in the oxidative stability of biodiesels prepared from oils of soy, corn, canola and sunflower was studied using the Rancimat method. The induction periods at 110 ºC, without and with the addition of CNSL at concentrations of 0.1, 0.5 and 1.0% m/m, were determined and clearly show an important increase in the oxidative stability proportional to the concentration of the additive. For example, with the addition of 0.1% m/m CNSL, the induction period, in hours, increased from 5.7 to 8.5 (soy biodiesel), from 1.7 to 4.0 (sunflower), from 4.3 to 9.3 (corn) and from 6.9 to 12.8 (canola). The rate constants of the oxidation reactions in presence of CNSL were also determined and their respective values are (in h-1): 0.77 ± 0.08, 2.48 ± 0.46, 0.94 ± 0.08, 0.51 ± 0.11. The activation parameters (enthalpy, ∆H*, entropy, ∆S*, and free energy of activation, ∆G*) for the oxidation reactions were determined.The influence of cashew nutshell liquid (CNSL) in the oxidative stability of biodiesels prepared from oils of soy, corn, canola and sunflower was studied using the Rancimat method. The induction periods at 110 ºC, without and with the addition of CNSL at285747755FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORsem informaçãosem informaçãosem informaçãoThe authors would like to thank the Conselho Nacional de Pesquisa Científica e Tecnológica, CNPq, the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES, for financial support and to Prof Adilson Beatriz, of the Federal University of Mat

Continuous monitoring of a transesterification reaction using an analytical balance

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOAn electronic analytical balance was used to monitor a transesterification reaction through density variations. To test the proposed system, we studied how the transesterification reaction was influenced by: (i) the addition of methanol to the oil ; (ii)291200204CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOsem informaçãoThe authors would like to thank the Conselho Nacional de Ciência e Tecnologia (CNPq) for financial support and the Students Assistance Service (SAE) of the University of Campinas (UNICAMP) for the scholarship granted to A. G. O.

Quantitative reflectance spot test for the determination of acetylsalicylic acid in pharmaceutical preparations

This paper describes a quantitative reflectance spot test procedure for the determination of acetylsalicylic acid (ASA) in pharmaceutical preparations. The method is based on the reaction of salicylic acid, obtained from the hydrolysis of ASA, with Fe(III) forming a deep blue-violet compound. Medicines containing ASA can be easily analyzed by the proposed method as it is not necessary to do any separation. The final mixture is placed on a sheet of filter paper, and the reflectance is directly measured. Nine commercial medicines containing acetylsalicylic acid were analyzed with the proposed method. The mean RSD was 0.9%. Results were compared with those obtained with the United States Pharmacopoeia recommended procedure (RSD 0.6%). The quantitative detection limit is 0.6 mg ASA in the working solution. For a degree of freedom n = 4 (n = n1+ n2 - 2) and a confidence coefficient a = 0.05 all the results agree under the tabulated t-Student test value (2.78).Este trabalho descreve um método para a determinação quantitativa de ácido acetilsalicílico (ASA) utilizando procedimento spot test e reflectância difusa. O método é baseado na formação do complexo de cor roxa intensa entre o ácido salicílico, obtido a partir da hidrólise alcalina do ASA, e íons Fe(III). O procedimento proposto permite a análise de medicamentos contendo ASA de forma fácil e simples, uma vez que não é necessário fazer separações. A reflectância da mistura final, colocada sobre um disco de papel de filtro, é medida diretamente. Foram analisados nove medicamentos comerciais contendo ASA cujos resultados apresentaram um desvio padrão relativo médio de 0,9%. O limite para a determinação quantitativa é de 0,6 mg de ASA na solução de trabalho. As análises feitas com o método proposto foram comparadas com outras análises, das mesmas amostras, segundo o procedimento recomendado pela United States Pharmacopoeia, onde se observou um desvio padrão relativo de 0,6%. Compararam-se os dois métodos utilizando-se o teste t de Student. Para um grau de liberdade n = 4 (n = n1 + n2 - 2) e um limite de confiança a = 0.05, onde t = 2,78, todos os resultados foram concordantes.327330Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Determination of the crystallographic radii of sodium and chloride ions

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.1763176

The determination of the stoichiometry of the mixed complex of vanadium with hydrogen peroxide and with 4-(2-Pyridilazo) Resorcinol

The present study reports details of the stoichiometric characterization of the mixed complex system, V(H2O2)PAR, formed when vanadium adequately reacts with hydrogen peroxide and with 4-(2-Pyridilazo)Resorcinol. Also the presence of polynuclear species was investigated in order to elucidate about unambiguous assignment of the molar absorptivity, stability constant and composition of the complex. Two mathematical treatments methods of the experimental results were employed. From the results it can be concluded that this system corresponds to a mononuclear complex with 1:1:1 stoichiometry.316319Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Separation of the glycerol-biodiesel phases in an ethyl transesterification synthetic route using water

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Biodiesel is obtained by the transesterification of vegetable oil (or fat) and alcohol, with methanol being the most used alcohol. Methanol can be replaced by ethanol; however, this alcohol acts as a surfactant in the reaction mixture, promoting a stable dispersion of the glycerol in biodiesel, which hinders the separation of the glycerol-biodiesel phases. In this study, it was found that the addition of 1% v/v water relative to the total volume of the reaction mixture expedites the separation of the phases by interrupting the emulsifying action of ethanol with an immediate separation of glycerol from biodiesel. The characterization of the produced biodiesels was performed using hydrogen nuclear magnetic resonance (H-1 NMR) and gas chromatography (GC). H-1 NMR indicated a 96.9% conversion of triglycerides to biodiesel. The fatty acid compositions of the synthesized ethyl and methyl biodiesels determined using GC are essentially the same.Biodiesel is obtained by the transesterification of vegetable oil (or fat) and alcohol, with methanol being the most used alcohol. Methanol can be replaced by ethanolhowever, this alcohol acts as a surfactant in the reaction mixture, promoting a stabl26917451750FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)sem informaçãosem informaçãoThe authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq, for financial suppor

Influence of water and ultraviolet irradiation on the induction period of the oxidation of biodiesel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Biodiesel degrades due to oxidative processes, causing a decrease in its quality. In the present work, it has been clearly shown that the incidence of ultraviolet radiation on biodiesels obtained from soy, canola, linseed and microalgae oils initiate oxidative processes which lead to the decrease in the induction period (IP) of the fuel. The influence of the residual water content of the same biodiesels on the oxidation process was also investigated with and without the incidence of ultraviolet radiation. Between 190 and 850 ppm of water in the biodiesel and without UV irradiation, no significant change in the IP values was observed under the experimental conditions.Biodiesel degrades due to oxidative processes, causing a decrease in its quality. In the present work, it has been clearly shown that the incidence of ultraviolet radiation on biodiesels obtained from soy, canola, linseed and microalgae oils initiate oxid284676680FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)sem informaçãosem informaçãoThe authors are grateful to CNPq for financial support and to Dr. Fabio Batista (EXTRAE-UNICAMP) who graciously provided the microalgae oi