It has been suggested that observations of classical criticality (with
beta = nu = 1/2, gamma = 1) in place of Ising-like behavior (beta con
gruent-to 0.32, etc.) in certain electrolytes might be associated with
charge-cavity, ion-ion interaction potentials varying with distance a
s 1/r4. We report that such forces are strongly screened at nonzero io
nic density, decaying as exp[-2kappar]/r2 when the direct Coulomb coup
ling is screened, as usual, by the factor exp [-kappar]. Within Debye-
Huckel theory, furthermore, representing the ions as spheres of differ
ent dielectric constant does not change any critical parameters. Conse
quently, other explanations of the experiments seem called for.