  The phenomenon of liquid-gas phase transition occurring in heavy ion
collisions at intermediate energies is a subject of contemporary interest.
Phase transition is usually characterized by the specific behaviour of state
variables like pressure, density, energy etc. In heavy ion collisions there is
no direct way of accessing these state variables and hence unambiguous
detection of phase transition becomes difficult. This work establishes that
signatures of phase transition can be extracted from the observables which are
easily accessible in experiments and these have similar behaviour as the state
variables. The temperature dependence of the first order derivative of the
order parameters related to the largest and second largest cluster size
(produced in heavy ion collisions) exhibit similar behavior as that of the
variation of specific heat at constant volume Cv which is an established
signature of first order phase transition. This motivates us to propose these
derivatives as confirmatory signals of liquid-gas phase transition. The
measurement of these signals in easily feasible in most experiments as compared
to the other signatures like specific heat, caloric curve or bimodality. This
temperature where the peak appears is designated to be the transition
temperature and the effect of certain parameters on this has also been
examined.
