A theoretical treatment in terms of a carrier model is made to obtain a generalized equation for the BLM conductance produced by the charged complex formation between plural multivalent cations and plural charged carriers.
The following experimental observations have been performed to deduce the ion transport mechanism across a BLM doped with Br-derivative of ionophore X537A (X-) according to the above-stated carrier model.The membrane conductance remarkably increases on the addition of X- to the aqueous solutions containing alkali metal cations.The membrane potential under a gradient of the concentration of monoor divalent cation shows quasi-Nernst behavior for the mono- or divalent cation, respectively.The ion conductance is proportional to approximately the square of the X- concentration, and it increases linearly with an increase in the ionic activities with a slope of 2 or 1 for the mono- or divalent cations, respectively, on a log-log plot.
Thus it is concluded that the HX2- complex acts as a carrier for two alkali monovalent cations (I-) leading to a complex of I2HX2, and this carrier complex combines with one alkali divalent cation (12+) as well as with one hydrogen ion (H+) leading to a complex of IH2X22+.
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