Browsing by Author "Liesegang, E C"

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    The ion exchange behaviour of some trivalent cations in aqueous monoethanolamine
    (1968) Scott, Nigel Harraway; Liesegang, E C; Churms S C
    This investigation of the behaviour of cation exchange resins in aqueous monoethanolamine has led to some interesting conclusions regarding the influence of the solvent onion exchange resins. The main results and conclusions, which have been discussed in detail in the preceding chapters, will now be summarised. The observed decrease in weight-swelling of the three resins in the various trivalent ionic states with a decrease in the dielectric constant of the ambient medium, by virtue of an increase in the monoethanolamine content of the external phase, may be attributed to :1) a decrease in the solvation tendency of the fixed ionic groups and counter-ions ; 2) an increase in ion-pair formation, resulting in a decrease in the number of osmotically active ions in the resin phase, and tin accompanying reduction in the osmotic pressure difference between resin and solution phases;3) an increase in association between resin anions and counter-ions, giving rise to a lower electrostatic potential of the polymer chains.
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    The mechanism of cathodic depolarization exhibited by sulphate-reducing bacteria during metallic corrosion processes
    (1975) Costello, John Anthony; Liesegang, E C
    The mechanism of the corrosive action of sulphate reducing bacteria of the genus Desulfovibrio towards ferrous metals has been investigated. This corrosive action is anomalous when considered in the light of established knowledge of corrosion processes, since it occurs in the absence of oxygen, at more or less neutral pH values and at ordinary ambient temperatures. The hypothesis of von Wolzogen Kuhr and van der Vlugt, published in 1934, proposing that enzymic catalysis of sulphate reduction by cathodic charge constituted a "cathodic depolarizing" process, which appears t o be widely accepted as the most likely mechanism for this corrosive effect, is evaluated critically here in the light of established electrochemical and biochemical knowledge. The theoret ical arguments presented in this thesis show that this process, if it does occur, is unlikely to affect corrosion rates. The experimental results presented here indicate that all cathodic depolarizing activity demonstrated in pure cultures of these organisms is attributable to the cathodic activity of dissolved hydrogen sulphide produced by the organisms. The conclusions of other workers, quoted in support of proposed enzymic catalysis of charge transfer from cathodes to redox dyes in laboratory systems, are considered, in view of experimental work performed during this investigation, to be a misinterpretation of experimental results.