The Debye-Hückel theory can be tested most accurately by changes in electrode potentials in electrochemistry. When current passes through a cell, ions are discharged at the anode and cathode with conservation of charge, so the overall change of energy brought about by screening corresponds to the the Brønsted-Bjerrum kinetic case with zero charge on the activated complex.

These precise measurements show that the Debye-Hückel theory is only a first approximation, and that deviations from it cannot be neglected even at quite low concentrations. An extension of the Debye-Hückel law is given by:

ln g_±   =   -(A |z₊z_- | I^½ )/(1 + BI ^½ )

The coefficient B can be explained in terms of specific short-range interactions between the ions and water or each other but is best regarded as an empirical parameter.

Information provided by: http://www.bpx.cov.ac.uk