A determinação de enxofre em plantas pelo método quelatométrico do BDTA

The present work reports a study of the chelatometric method (by EDTA titration) for determination of sulfate in plant materials. A preliminary study about the indicator, conditions for the good precipitation of barium sulfate, and other influences on the method were performed. The presence of cations in the plant extracts did not cause interferences because they were separated using a cation exchange resin. The phosphate interferes and this ion can be removed by precipitation as ferric phosphate, adding ferric iron, acetate and ammonium hydroxide. Sulfate was determined in aqueous solutions, containing several ions, with good results. In order to compare the chelatometric (based in the proposed technique) and the gravimetric methods, in the determination of total sulfur in plants, five replications of different plant materials were analysed by both methods. The data obtained allowed to conclude that the technique proposed is good and the accuracy satisfactory. The determination of sulfur-sulfate was performed by the proposed method with satisfactory results.Neste trabalho são relatados estudos a respeito do método quelatométrico de determinação de sulfato, baseado na titulação do bário residual com solução de EDTA, após a precipitação do citado ânion na forma de sulfato de bário. Foram estudados aspectos relativos ao emprego de diferentes indicadores e passou-se a preconizar o uso de solução de púrpura de ftaleína a 0,2%. São descritos experimentos relativos à determinação de sulfato em soluções puras, observando-se o período de precipitação e a influência de diversos ânions. Finalmente, tendo por base os dados obtidos, é preconizada urna marcha analítica para determinação de enxôfre total e enxôfre-sulfato em material vegetal. Os resultados obtidos quando se empregou a técnica proposta na determinação de sulfato em materiais vegetais, foram comparados com aquêles fornecidos pelo método gravimétrico, baseado na pe-sagem do sulfato de bário

Estudos sôbre a neutralização do caldo de cana nas usinas de açúcar: I - determinação do CaO e MgO totais e CaO disponível da Cal

This paper is the first of several papers about the studies of neutralization of sugar cane juice, after treatment with SO2 in the cane sugar fabrication. The present work reports a study about the chelatometric method for the determination of total calcium oxide and magnesium oxide of lime and the available lime. The proposed method (by EDTA titration) for determining available lime was compared with the method based on sulfuric acid titration, with good agreement. The results showed that the chelatometric method is rapid and affords good precision. For the study about the neutralization of sugar cane juice, after treatment with SO2, were employed samples of lime containing several per cent of available lime. The quantities of lime to be added, to one liter of treated juice, was calculated based in the total calcium oxide of the lime. The solid samples of lime were added to the juice slowly and the material shaken intermittently during the period of fifteen minutes after the addition of lime. The pH was determined both 15 minutes and 2 1/2 hours after the addition of lime. Them it was brought to ebullition, cooled at room temperature and the pH was again determined. The results permit to conclude that the samples containing small amounts of available lime showed the poorest neutralization. Even with samples containing high percentage of available lime it was not possible to obtain a juice with pH 7,0 after the treatment, probably due to the presence of carbonates in the samples of lime. This study showed that the principal characteristic of lime to be employed in the juice neutralization is the available lime.Neste trabalho, que faz parte de uma série de pesquisas relacionadas com a neutralização do caldo de cana nas usinas de açúcar, é descrita a técnica de determinação quelatométrica do CaO e MgO totais e CaO disponível da cal. Os resultados fornecidos pela técnica preconizada foram comparados com aqueles obtidos através do emprêgo de métodos usuais. São também apresentados os primeiros estudos efetuados a respeito da capacidade neutralizadora da cal, em função do seu teor em oxido de calcio total e disponível, quando empregada na forma solida, na neutralização do caldo de cana

Determinação das várias formas de fósforo em tortas de filtro rotativo

This paper describes analytical methods for determining the various phosphorus fractions in filter cake. These fractions can be classified as to their solubility in several extractants: water; 2% citric acid; neutral ammonium citrate; 0,5 N sulfuric acid. All procedures employed colorimetric methods, using the reagents according to the needed sensitivity. The metodology for the determination of total phosphorus after a dry solubilization procedure is described as well as the methodology for organic phosphorus determination. The inorganic phosphorus predominate in the samples with a range of 2,3 to 0,8%, depending on the origin and harvesting period. The best procedure was the analysis of the cake in its natural condition (moist cake) using the extraction by 2% citric acid solution.São descritos métodos analíticos visando a determinação das várias frações de fósforo presente em tortas de filtro rotativo. Essas frações podem ser classificadas de acordo com a sua solubilidade em diversos extratores, a saber: água, solução de ácído cítrico a 2%, solução neutra de citrato de amônio, solução de ácido sulfúrico 0,5 N. Também é apresentada a descrição da metodologia necessária para a determinação do teor total de fósforo por via seca e para a determinação de fósforo orgânico . Todas as determinações foram feitas por métodos colorimétricos, adaptando-se os reativos de acordo com a sensibilidade desejada. A forma predominante foi a inorgânica, com os teores variando de 2,3 a 0,8% dependendo da origem e período da safra. Conclui-se que o melhor procedimento é a análise da torta na sua condição natural (úmida) com o fósforo sendo extraído com solução de ácido cítrico a 2%

Determinação do enxôfre orgânico do solo pelo método colorimétrico do cloranilato de bário

This paper describes a direct method for determining organic soil sulfur. By the proposed method the soil is ashed in an eletric tube-furnace at 800°C in a stream of oxygen and the escaping gases were absorbed by oxygen peroxide solution. After the ashing the excess of oxygen peroxide is eliminated by ebullition, and the resulting sulfate is determined by the colorimetric method based on the reaction with barium chloranilate, and the absorbance was determined at 308 milimicrons. The results obtained allowed to conclude that the tech nique proposed is good and the accuracy satisfactory.O presente trabalho descreve uma nova técnica para determinação direta do enxofre orgânico do solo. No método preconizado os solos são incinerados a 800°C, em tubos de porcelana, sob corrente de oxigênio. Os gases formados sao recebidos em solução de peróxido de hidrogênio e, em seguida, o excesso do oxidante é eliminado por ebulição. O sulfato formado é determinado pelo método colorimétrico do cloranilato de bário, mediante leituras a 308 molimicrons. Foram realizados estudos sobre vários fatores que podem influir no método e a determinação do enxofre orgânico em cinco solos, pertencentes a diferentes grandes grupos, mostrou uma precisão razoável

Absorção de zinco pela cana de açúcar, Co 419, em função da idade

The status of zinc in sugar cane, variety Co 419, troughout its life cyle, was studid in samples cut monthly, from the 6th to 15th month, from an experiment carried on under the conditions of soil and climate prevailing in Piracicaba, State of São Paulo, Brazil. The experiment consisted of 6plots, 3 fertilized and 3 unfertilized. The fertilized ones received 40 kg of N (ammonium sulfate), 100 kg P2O5 (superphosphate) and 40 kg K2O (potassium cloride) per hectare, just before planting. The zinc content was determined by the Zincon method, after separation of zinc from other ions by means of the ion Exchange Resin III, Merck. The results obtained show that there was a tendency to decrease the zinc level in the stalks, whereas it kept more or less constant in the leaves; there was an exception in January, when the zinc level in the stalks had a sharp raise: 38-90-20 and 28-60-23 ppm for the fertilized an unfertilized treatments. There was a parallelism in the absorption of zinc by the plants from 4 hills of both treatments, through the whole - plantcycle but, the total amount taken up was higher with the fertilized plot due to its greater mass production