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On the concept of ionicity in ionic liquids
journal contribution
posted on 2009-01-01, 00:00 authored by D MacFarlane, Maria ForsythMaria Forsyth, E Izgorodina, A Abbott, G Annat, K FraserIonic liquids are liquids comprised totally of ions. However, not all of the ions present appear to be available to participate in conduction processes, to a degree that is dependent on the nature of the ionic liquid and its structure. There is much interest in quantifying and understanding this ‘degree of ionicity’ phenomenon. In this paper we present transport data for a range of ionic liquids and evaluate the data firstly in terms of the Walden plot as an approximate and readily accessible approach to estimating ionicity. An adjusted Walden plot that makes explicit allowance for differences in ion sizes is shown to be an improvement to this approach for the series of ionic liquids described. In some cases, where diffusion measurements are possible, it is feasible to directly quantify ionicity via the Nernst–Einstein equation, confirming the validity of the adjusted Walden plot approach. Some of the ionic liquids studied exhibit ionicity values very close to ideal; this is discussed in terms of a model of a highly associated liquid in which the ion correlations have similar impact on both the diffusive and conductive motions. Ionicity, as defined, is thus a useful measure of adherence to the Nernst–Einstein equation, but is not necessarily a measure of ion availability in the chemical sense.
History
Journal
Physical chemistry chemical physicsVolume
11Issue
25Pagination
4962 - 4967Publisher
Royal Society of ChemistryLocation
Cambridge, EnglandPublisher DOI
ISSN
1463-9076eISSN
1463-9084Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2009, Owner SocietiesUsage metrics
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