  In this work a novel method to evaluate the liquid-vapor critical temperature
using a generalization of the Microcanonical-ensemble computer simulation
method (MCE) is presented. The isotherms of the chemical potential versus
densities are obtained for a square-well (SW) fluid with interaction range
$\lambda/\sigma = 1.5$: From these curves it can be extracted the critical
temperature for different system sizes observing the change of the slope from
the chemical potential's curve in the critical region as function of the
temperature. Working with different systems sizes and Finite Size Scaling (FSS)
Theory the critical temperature $T_c=1.2180(29)$ and the critical exponent
$\nu=0.65(3)$ are obtained, without previous knowledge of $T_c$ or $\nu$. These
results are in good agreement with the reported values for this system.
