Determinação de potássio em fertilizantes por fotometria de chama

This paper deals with the determination of potassium in fertilizers by the flame photometric method. A preliminary study was performed in order to know the relationship between potassium concentration and readings in the Coleman flame photometer, model 21. It was verified a linear relation when the concentration of potassium was in the range of 0 and 30 ppm. The presence of some ions like calcium, magnesium, iron, sodium, phosphate, sulfate and ammonium were studied and showed that calcium and magnesium cause no interference in the method. Ammonium caused a slight interference when 550 ppm of NH4+ and 10 ppm of potassium were present. With 20 ppm of potassium the influence of ammonium was observed only with 995 ppm. Sulfate caused a moderate influence and phosphate interfered, giving lower results. The determination of potassium, with five replications, in three fertilizer mixtures, were performed in solutions that underwent a previous separation of phosphate and sulfate by an anion exchange resin and in solutions not purified by ion adsorption. The results showed good agreement indicating it is not necessary the separation of phosphate and sulfate when there is a several fold dilution of the solution. The method for determining potassium in fertilizers by flame photometry is very rapid and afford a good precision.O presente trabalho relata um estudo sobre a determinação do potássio em fertilizantes por fotometria de chama e empregando o aparelho Coleman, modêlo 21. A precisão do método foi estudada, aplicando-o na análise de 3misturas contendo os fertilizantes sulfato de amônio e superfosfato simples ou triplo e uma quantidade conhecida de potássio na forma de sal puro, para análise (KC1 p.a.). As determinações do potássio foram executadas nas soluções das mencionadas misturas, após eliminar os ânions sulfato e fosfato com a resina Amberlite IR-4B (OH). Os dados obtidos evidenciaram que o método em questão além de ser muito rápido, forneceu resultados satisfatórios, quando se consideram as diluições necessárias para as determinações. Outras determinações executadas simultaneamente, e em soluções das mesmas misturas, mas sem eliminar os ânions sulfato e fosfato, forneceram dados próximos aos obtidos com a eliminação dos citados ânions

Ruminal in vitro fermentation kinetics and chemical composition of Sorghum cv. Nutritop at different stage of regrowth.

The objective was to estimate the ruminal degradation kinetics and chemical composition of Sorghum cv. Nutritop at different stages of regrowth, as fed for background lambs

Dry matter intake from beef cattle grazing natural grassland with different intensification levels.

Estimating dry matter intake from grazing animals remains a challenge. Among the indicators currently used, n-alkanes have been shown to be a good alternative, especially in heterogeneous environments such as natural grasslands

Emissões de metano por novilhos de corte em pastagem natural.

A pastagem natural é a principal fonte de alimento de bovinos de corte no Rio Grande do Sul, entretanto poucos são os dados sobre emissões de metano de novilhos de corte neste ambiente. O objetivo foi avaliar a emissão de metano por bovinos de corte em pastagem natural.Editora técnica Claudia Cristina Gulias Gomes

Ti-25Nb-25Ta alloy treated by plasma electrolytic oxidation in phosphoric acid for implant applications

Among titanium alloys with non-toxic elements, the Ti-25Nb-25Ta alloy has good elastic behavior for applications in osseous implants, biocompatibility, and excellent corrosion resistance. The present study aimed to better the biocompatibility characteristics of Ti-25Nb-25Ta alloy modifying its surface through Plasma Electrolytic Oxidation (PEO) treatment. The formed oxide coating is amorphous and composed of two distinct porous formations: smaller hole-shaped pores and larger volcano-like pores. The regions with the formation of smaller pores and in the hole shaped presented the highest atomic percentage of the chemical element phosphorus. Nanoindentation tests have shown that the hardness of the Ti-25Nb-25Ta alloy is slightly lower than the commercially pure grade 2 titanium (a material used as reference), while elastic modulus measurements of Ti-25Nb-25Ta presented more suitable values for implant application (lower values when compared with titanium reference). After PEO treatment there were significant mechanical surface improvements (increased fairly surface hardness and decreased elastic modulus) for application in osseous tissue. Despite the Ti-25Nb-25Ta alloy presented excellent characteristics for applications in hard biological tissues, the PEO treatment better its features.Keywords: Titanium alloy, Ti-25Nb-25Ta, nanoindentation, mechanical properties, Plasma Electrolytic Oxidation.