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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 13 (1967), S. 395-396 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 250-258 
    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 kinetic model was developed to describe the rate of reaction between chromium(III) and polyacrylamide (PAAm) that leads to the crosslinking or gelation of the polymer. Cr(III) was added directly to solutions of polyacrylamide which had a degree of hydrolysis of approximately 4%. The unreacted Cr(III) was separated from that which had reacted with the polymer by equilibrium dialysis and measured by atomic absorption.The rate of the reaction was described by an empirical model based on the assumption of invariant polymer group concentration during the reaction. The order of reaction was determined to be 1.32 for Cr(III), 0.8 for the polymer group, and -1.0 for hydrogen ion. Modifications were made to the model to allow for variation during reaction of the concentration of the polyacrylamide reactive group. The modified model accurately described the reaction rate for Cr(III) concentration ranging from 0.19 to 1.2 mM, polyacrylamide concentrations from 6.9 to 69 mM, and pH values from 4.0 to 5.5.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-904X
    Keywords: drug dissolution ; rotating disk ; mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A model has been developed to describe the mass transport and reaction of ionizable compounds where mass transfer is caused by convection and diffusion from a rotating disk. Dissolution rates of benzoic acid, 2-naphthoic acid, and indomethacin in aqueous solutions of high ionic strength (I = 0.5 with potassium chloride) at 25°C were investigated. The model includes the effects of diffusion, convection, and simultaneous acid/base reaction at all points in the region adjacent to the dissolving solid. The solution of the transport equations is obtained numerically with an iterative algorithm which uses (a) closure of all material balances and (b) equilibria at the solid/liquid surface as constraints. The model solution yields both the flux of the dissolving acid and the concentration profile of each component. Reduced values of all reaction rate constants are used in the region adjacent to the dissolving surface to allow convergence of the computation. Although nonequilibrium concentration values are calculated, it is shown that the theoretical dissolution rate determined as the solution of the model is insensitive to the magnitude of the rate constants as their maximum useable values are approached. Comparisons of the model results with experimentally determined fluxes show close agreement and confirm that the transport mechanisms in the model formulation are consistent with the measured values. Further, the inclusion of convection allows accurate calculations without utilization of an arbitrary boundary layer thickness. Accurate dissolution rates can be determined using this technique under a wide range of conditions, except at low pH.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Methods for Partial Differential Equations 10 (1994), S. 677-687 
    ISSN: 0749-159X
    Keywords: Mathematics and Statistics ; Numerical Methods
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: von Rosenberg developed an explicit finite-difference scheme for solution of the linear convection-conduction partial differential equation in one space dimension. The method is stable and accurate when a dimensionless ratio of dispersion to convection is between zero and one. In this work, the von Rosenberg method was applied to a linear, one space dimensional set of coupled convection-conduction equations. The system examined involves the change in temperature resulting from a fluid flowing through a stationary porous solid with heat transfer between the fluid and solid phases. The equations, which describe heat transfer in each phase, were solved simultaneously and, thus, the solution method was required to be implicit rather than explicit. It was observed that when the interphase convective heat-transfer rate was small relative to the fluid velocity, an implicit solution of the von Rosenberg weighted equations provided a good solution, but when the interphase convective heat-transfer rate was relatively large, a modified weighting on the equations provided a more accurate, stable solution. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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