Estuda-se a condutibilidade equivalente a 25 °C de soluções aquosas de hexacianocobaltato(111) e de hidroxopentacianocobaltato( 111) de potássio. Verifica-se que a variação com a concentração se afasta do previsto pela lei limite de Onsager, devido ao fenómeno de associação iónica, cujo coeficiente se calcula.

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A new linearised model for the transient operation of a packed column, covering both total reflux and production conditions, was developed. A height-dependent initial condition makes possible the use of this model in the optimization of the column start-up procedure.

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The design of the chemical reactor is based on a detailed study of the process, which together with appropriate design procedures and analysis leads to the determination of reactor size at the best operating conditions for the desired rate of production. The detailed study of the process comprises: the reaction kinetics; effect of physical phenomena accompanying the reaction and interaction of the operating parameters on the reaction rate and yield; materials of construction and process economics.

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Composting provides a means of converting the organic wastes of modern society into a humic material of importance to the maintenance of soils in a state of adequate fertility. The paper reviews the chemical and physical parameters which need consideration in the design of a practical composting process.

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Large quantities of plastics waste arise each year which require disposal. These quantities are expected to double or triple in the next five years and it becomes increasingly important therefore to handle these wastes in the most effective way. The recent substantial rises in costs of virgin polymeric materials should make recycling a more attractive proposition than dumping. The range of alternatives available for disposal re-use, recycling, or recovery are explored.

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Neste artigo estuda-se a influência de diversos factores (concentração total da alimentação, razão Cl - SO4 no influente, percentagem de regeneração da coluna aniónica, fuga da coluna catiónica) na capacidade útil da coluna aniónica duma cadeia clássica de desmineralização da água.

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Descrevem-se as acções de saneamento levadas a cabo em Portugal, durante o combate à epidemia de cólera do Verão de 1974, e dá-se conta dos bons resultados obtidos. Depois de unia breve revista dos antecedentes, descreve-se a epidemia e refere-se o espectro global das acções desenvolvidas na prevenção e luta contra a disseminação da doença, segundo três linhas directoras: a vigilância epidemiológica, o saneamento ambiental e a educação sanitária. Realçam-se as medidas de saneamento nos domínios dos abastecimentos de água, dos esgotos de águas usadas e dos alimentos, principalmente legumes e moluscos bivalves.

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