Editing Acid (section)

==Lewis acid strength in non-aqueous solutions==
[[Lewis acids]] have been classified in the [[ECW model]] and it has been shown that there is no one order of acid strengths.<ref>{{cite journal|author1=Vogel G. C. |author2=Drago, R. S. |year=1996|journal=Journal of Chemical Education|volume=73|pages=701–707|title=The ECW Model|issue=8 |bibcode=1996JChEd..73..701V|doi=10.1021/ed073p701}}</ref>  The relative acceptor strength of Lewis acids toward a series of bases, versus other Lewis acids, can be illustrated by [[ECW model|C-B plots]].<ref>Laurence, C. and Gal, J-F.  Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 ISBN 978-0-470-74957-9</ref><ref>{{cite journal|author1=Cramer, R. E. |author2=Bopp, T. T. |year=1977|title= Graphical display of the enthalpies of adduct formation for Lewis acids and bases |journal= Journal of Chemical Education |volume=54|pages=612–613|doi= 10.1021/ed054p612}} The plots shown in this paper used older parameters. Improved E&C parameters are listed in [[ECW model]].</ref>  It has been shown that to define the order of Lewis acid strength at least two properties must be considered. For Pearson's qualitative [[HSAB theory]] the two properties are [[HSAB theory|hardness]] and strength while for Drago's quantitative [[ECW model]] the two properties are electrostatic and covalent.