  A phase transition signature associated with cumulants of the largest
fragment size distribution has been identified in statistical
multifragmentation models and examined in analysis of the ALADIN S254 data on
fragmentation of neutron-poor and neutron-rich projectiles. Characteristics of
the transition point indicated by this signature are weakly dependent on the
A/Z ratio of the fragmenting spectator source. In particular, chemical
freeze-out temperatures are estimated within the range 5.9 to 6.5 MeV. The
experimental results are well reproduced by the SMM model.
