  The constant-volume heat capacity, C_V(T, rho), of the restricted primitive
model (RPM) electrolyte is considered in the vicinity of its critical point. It
is demonstrated that, despite claims, recent simulations for finite systems do
not convincingly indicate the absence of a divergence in C_V(T, rho)--which
would point to non-Ising-type criticality. The strong qualitative difference
between C_V for the RPM and for a Lennard-Jones fluid is shown to result from
the low critical density of the former. If one considers the theoretically
preferable configurational heat-capacity density, C_V/V, the finite-size
results for the two systems display qualitatively similar behavior on
near-critical isotherms.
