Abstract
Two extraction constants (Kex± and Kex) for extraction of silver picrate (Ag﹢Pic﹣) by benzo-15-crown-5 ether (B15C5) and benzo-18-crown-6 one (B18C6) into 1,2-dichloroethane (DCE) and dichloromethane (DCM) were determined at 298 K and given values of ionic strength. Here, Kex± and Kex were expressed as [AgL﹢]o[Pic﹣]o/[Ag﹢][L]o[Pic﹣] and [AgLPic]o/[Ag﹢][L]o[Pic﹣], respectively: L symbolizes B15C5 or B18C6 and the subscript “o” denotes the organic phase composed of DCE or DCM. Individual distribution constants (KD,Pic) of picrate ion, Pic﹣, into the two diluents were also determined with the determination of Kex. From comparison of these KD,Pic values with those standardized, interfacial potential differences () at extraction equilibria were evaluated. Then, using these values, relations of the experimentally-determined logKex± or logKex values with their electrochemically-standardized ones were precisely discussed. Consequently, it was indicated that logKex± should be expressed as a function of .
Highlights
Individual distribution constants (KD,A) of single anions (A−), such as picrate ion (Pic−) and MnO−4, into various diluents or organic (o) phases have been determined in course of determination of extraction constants (Kex) for the extraction of some salts, MIA and MIIA2, by crown compounds (L) [1]-[4]
We determined the KD,Pic and Kex values by the silver picrate (AgPic) extraction-experiments with benzo-15crown-5 ether (B15C5) and benzo-18-crown-6 one (B18C6) into less-polar DCE and dichloromethane (DCM), in order to examine the deviations of the logKD,Pic values from the log
Regression lines of the other systems were of a correlation coefficient (R) = 0.196 for the B15C5/DCM system, 0.969 for B18C6/DCM and 0.823 for B15C5/
Summary
Individual distribution constants (KD,A) of single anions (A−), such as picrate ion (Pic−) and MnO−4 , into various diluents or organic (o) phases have been determined in course of determination of extraction constants (Kex) for the extraction of some salts, MIA and MIIA2, by crown compounds (L) [1]-[4]. The logKD,A values were −0.65 for A− = Pic− and −2.137 for MnO4− in the CsA extraction by dibenzo-24-crown-8 ether derivatives into DCE [4]. We determined the KD,Pic and Kex values by the silver picrate (AgPic) extraction-experiments with B15C5 and B18C6 into less-polar DCE and dichloromethane (DCM), in order to examine the deviations of the logKD,Pic values from the log. In course of this examination, the differences were discussed by introducing interfacial potential differences (∆φeq) at extraction (and distribution) equilibria [9] in an extraction model. It was considered how the extraction constants, Kex and Kex±, were expressed by these. The Kex± values were calculated from the Kex values and other equilibrium constants determined in this study
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