Strong and weak field criticality of 2D liquid gas transition

Finite size scaling (FSS) analysis of the liquid gas criticality is complicated by the absence of any broken symmetry. This, in particular, does not allow a straightforward finding of the coexistence line and the critical point. The numerical flowgram (NF) method is adapted for a controlled determination of the coexistence line and the critical point, with the critical indices $\mu,\, \nu$ measured within 1-2% of the total error. The approach based on the NF for measuring the non-analytical corrections to the diameter - the mean density of the liquid and gas phases along the coexistence line - is outlined. Our analysis is a first step toward a general evaluation of isolated critical and multicritical points.