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  • 1
    Electronic Resource
    Electronic Resource
    Extractable chromium determination in soils by AAS (1995)
    Springer
    Microchimica acta 119 (1995), S. 251-258 
    Details
    ISSN: 1436-5073
    Keywords: extractable chromium ; soils ; EDTA extracts ; acetic acid extracts ; FAAS ; releasing agent oxine and ETAAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The lixiviation of trace metals from soils using selective extractants gives valuable information, especially for agricultural purposes. The two reagents validated by a group of European researchers coordinated by the Measurements and Testing Program (MAT) of the Commission of the European Community, in single extraction procedures, are EDTA 0.05 moll−1 and CH3COOH 0.43 moll−1. This paper reports the effect of these extractants upon chromium determination in extracts by AAS. Matrix effects were studied in extracts of two soils of different origin: a terra rossa soil from a Mediterranean area and a sewage amended soil. For the FAAS technique, the matrix effects were studied for air-acetylene and nitrous oxide-acetylene flames and using Cr(VI) and Cr(III) as standard solutions. The interfering effects observed are circumvented by the use of 1% 8-hydroxyquinoline as suppressor agent. For the ETAAS technique, charring and atomization curves were obtained for extracts in each reagent and after setting up the graphite furnace program, matrix effects were studied. Different matrix modifiers (Mg(NO3)2, Pd and Triton X-100) were also tested. Once the analytical method had been established, single extraction procedures were applied in the two soils, determining the percentage of extractable chromium in relation to the total content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244004
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of candidate certified reference materials for the quality control of EDTA-and acetic acid-extractable trace metal determinations in sewage sludge-amended soil and terra rossa soil (1995)
    Springer
    Microchimica acta 120 (1995), S. 289-300 
    Details
    ISSN: 1436-5073
    Keywords: extraction ; soils ; trace elements ; candidate CRMs ; reference materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of extractable trace metal contents in soil using single extraction procedures is currently performed in many laboratories to assess the bioavailable metal fraction (and related phytotoxic effects) and the accessability to the environment (e.g. contamination of ground waters). Owing to the need for validation of the extraction schemes used and of the analytical techniques, the EC Measurements and Testing Programme (formerly BCR) has organized a project for improving the quality of determination of extractable trace metal contents in soil, the first step being an interlaboratory study to adopt common extraction procedures and the second being a certification campaign to certify two soils for their extractable trace element contents following these procedures. This paper gives a brief overview of the project organisation and describes the preparation, homogeneity and stability studies of two soil candidate reference materials (sewage sludge-amended and terra rossa soils).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244439
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  • 3
    Electronic Resource
    Electronic Resource
    Model for colloidal fouling of membranes (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 368-376 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A proposed theoretical model describes colloids deposition on a membrane surface accounting for surface interactions. A mass-transfer equation links the deposition rate to hydrodynamic conditions (permeation and tangential flow through a boundary layer thickness, δ) and to physicochemical properties of the suspension (diffusion, D, and potential barrier between particles, VB). This equation predicts the existence of a critical flux, Jcrit, for ultrafiltration, reverse osmosis, or microfiltration of large-size colloids as: \documentclass{article}\pagestyle{empty}\begin{document}$$ J_{crit} = \frac{D}{\delta}ln \left({\frac{{V_B}}{\delta}} \right) $$\end{document} Some of the trends observed when processing protein solutions are explained by this model. Previous experimental data for various colloids or our data with a clay suspension in the presence of electrolytes are also compared to predictions of our model. It explains the “flux anomaly” for particle sizes between 10 nm and 1 μm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410218
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of the lubricant properties of candelilla wax in unplasticized PVC/wax systemsPart of this work integrates the Masters in Polymer Science and Technology Thesis of V. Valverde-Herrera, at U. A. de C. (1995). (1995)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 1 (1995), S. 162-169 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper reports on the evaluation of a natural product, candelilla wax, as a possible lubricant for unplasticized PVC formulations stabilized with lead or barium/cadmium chemicals. The lubricant effect of two types of wax (commercial grade and purified by solvent extraction) was evaluated by torque and extrusion rheometry and by differential scanning calorimetry. Commercial lubricants (Loxiol) were used for comparison. The results show that candelilla wax may be used as a lubricant (mainly of the external type) for unplasticized PVC; however, care must be taken when designing formulations to avoid over-lubrication, specially when lead-based thermal stabilizers are used.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730010310
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