  The gradual insertion method for direct calculation of the chemical potential
by molecular simulation is applied in the NpT ensemble to different quadrupolar
two-centre Lennard-Jones fluids at high density state points. The results agree
well with Widom's test particle insertion but show at very high densities
significantly smaller statistical uncertainties. The gradual insertion method,
which is coupled here with preferential sampling, extends the density range
where reliable information on the chemical potential can be obtained.
Application details are reported.
