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  • 1
    Electronic Resource
    Electronic Resource
    Intermediate Hamiltonians for the lithium atom (1972)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 6 (1972), S. 793-795 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560060420
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  • 2
    Electronic Resource
    Electronic Resource
    Water and ion flow across cellulosic membranesThis is part of the work performed for the partial fulfillment of the requirements for the degree of Doctor of Philosophy at the University of Florida. (1959)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 1 (1959), S. 133-143 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The primary objective of this investigation has been to explain why cellulose acetate behaves as a semipermeable membrane in saline water. To explain this phenomenon, two different mechanisms for the transfer to water and ions through cellulose acetate membranes were formulated. Those ions and molecules that cannot enter into hydrogen bonding with the membrane are transferred by hole-type diffusion. The rate of diffusion appears to be governed by a water-cellulose acetate structure. The reaction between water and the cellulose polymers to form bound water regions is favored by compressing the membrane. As pressure is applied on the membrane, more bound water is produced, which causes the rate of hole-type diffusion to decrease. On the other hand, those ions and molecules that can associate with the membrane and are transported through it by alignment-type diffusion. The formation of the water-cellulose acetate structure does not appreciably diminish the diffusion rate of water through the membrane. Cellulose acetate begins to behave as an effective semipermeable membrane in saline water when it is compressed sufficiently to retard greatly the diffusion of NaCl. Several types of experiments were conducted to support these hypotheses. The most important evidence was obtained from resistance experiments. The electrical resistances of specific ions was measured across cellulose acetate at various pressures by using permselective membranes to prevent migration of the ion of opposite charge. It was observed that the rate of diffusion of those ions that cannot combine with the membrane actually does decrease as the membrane is compressed. The rate of diffusion of H3O+, which can enter into hydrogen bonding with cellulose acetate, is much higher and is not appreciably reduced as the membrane is compressed. These resistance-pressure relationships are correlated with the semipermeability of the cellulose acetate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1959.070010202
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrafiltration of salt solutions by ion-excluding and ion-selective membrancesBased on the Ph.D. dissertation of H. G. Spencer, University of Florida, August 1959. (1960)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 4 (1960), S. 354-361 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Salt-filtering properties of several polymeric membranes were investigated at 40 atm. applied pressure. The ultrafilters were classified as ion-excluding or ion-selective membranes according to their ohmic resistance to the ions of the sodium chloride test solution. Membranes containing hydrophilic groups which have a high resistance to both cations and anions are classified as ion-excluding. Polyelectrolyte membranes with high resistance to cations only are considered to be ion-selective. In addition to cellulose acetate, which has been investigated previously, cellulose isobutyrate, cellophane-supported polyvinyl methyl ketone, and cellophane-supported polyvinyl acetate were found to be ion-excluding membranes. The amorphous membranes, polyvinyl methyl ketone and polyvinyl acetate, do not reject salt alone; the cellophane appears to provide a supporting matrix which restricts the interchain distances in the interfacial region. Membranes composed of mixtures of the 1:1 copolymer of methyl vinyl ether and maleic anhydride with polyvinyl alcohol were durable, ion-selective salt filters. Baking these membranes reduced swelling and flow rate and increased salt rejection. Those membranes containing high concentrations of the copolymer were flimsy and required bonding to a cellophane supporting membrane in order to obtain high salt rejection. The effects of process variables on the ultrafiltration properties of the ion-selective membranes were also investigated. The salt rejection by either class of membrane depends on both a high concentration of the required functional groups and restricted interchain distances. Despite differences in the mechanism, each class behaves as a filter, in that the smaller the pores, the more effective the separation and the lower the flow rate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1960.070041213
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    Paper (German National Licenses)
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