  We investigate the connection between the well known Sherrington-Kirkpatrick
Ising Spin Glass and the corresponding Lattice Gas model by analyzing the
relation between their thermodynamical functions. We present results of replica
approach in the Replica Symmetric approximation and discuss its stability as a
function of temperature and external source. Next we examine the effects of
first order Replica Symmetry Breaking at zero temperature. We finally compare
SK results with ours and suggest how the latter could be relevant to a
description of the structural glass transition.
