  Measurement of M, the total multiplicity, for central collision between
comparable mass heavy ions can provide a signature for first order phase
transition. The derivative of M with respect to E*/A where E* is the excitation
energy in the centre of mass and A the total mass of the dissociating system is
expected to go through maximum as a function of E*. Theoretical modelling shows
that this is the energy where the specific heat Cv maximizes which typically
happens at first order phase transition. The measurement of total M is probably
feasible in more than one laboratory.
