ISSN:
1572-8927
Keywords:
Relaxation effects
;
electrolyte conductance
;
limiting conductance
;
ionic association
;
acetonitrile
;
formamide
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract In a recent derivation of relaxation effects in the Debye-Hückel-Onsager theory of electrolyte conductance, with a length parameter a, terms are included which have been omitted in earlier treatments (see Appendix). The new expression was applied earlier in a reanalysis of conductance data for aqueous solutions and is applied here to solutions in acetonitrile and in formamide, representing respectively dielectric constants considerably lower and higher than water. As in aqueous solutions, a minimum standard deviation is found over a wide range of (K A,a) pairs without much effect on A 0 , so that only approximate determinations ofK A are possible. On the whole, the most appropriate length parametera is the physical contact distance between counterions, not a fixed radius, independent of ionic size, such as the Bjerrum value, nor a much larger radiusR serving as a boudary between free and associated ions in the ionic atmosphere about a central ion. Relaxation effects calculated by the new analysis are smaller than those from previous expressions for equal values ofa, and this leads to considerably larger values ofK A than in the original papers. As a consequence, specific short-range ion-ion and ion-solvent forces in most solutions predominate over electrostatic attraction between counterions in their contribution toK A. A table of limiting equivalent conductance based on the A 0 values obtained is presented; this differs little from previous tables since A 0 values obtained by the new analysis are similar to those obtained originally.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00650812
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