  We study the effect of quenched disorder in the thermodynamic magnitudes
entailed in the first-order vortex phase transition of the extremely layered
Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8 + \delta}$ compound. We track the
temperature-evolution of the enthalpy and the entropy-jump at the vortex
solidification transition by means of AC local magnetic measurements. Quenched
disorder is introduced to the pristine samples by means of heavy-ion
irradiation with Pb and Xe producing a random columnar-track pins distribution
with different densities (matching field $B_{\Phi}$). In contrast with previous
magneto-optical reports, we find that the first-order phase transition persists
for samples with $B_{\Phi}$ up to 100\,Gauss. For very low densities of
quenched disorder (pristine samples), the evolution of the thermodynamic
properties can be satisfactorily explained considering a negligible effect of
pinning and only electromagnetic coupling between pancake vortices lying in
adjacent CuO planes. This description is not satisfactory on increasing
magnitude of quenched disorder.
