  Master curves of the relaxation time, tau, or viscosity, eta, versus
T^-1V^-x, where T is temperature, V the specific volume, and x a material
constant, are used to deduce the effect of pressure on the dynamic crossover
and the fragility. The crossover is determined from the change in slope of
derivative plots of the relaxation times or viscosities. We confirm our
previous findings that the value of tau or eta at the crossover is independent
of both T and P; that is, the dynamic crossover is associated with a
characteristic value of the relaxation time. Previous determinations were
limited to liquids having crossovers occurring at large values of tau (> 10
microsec), whereas by interpolating within T^-1V^-x space, we extend the
analysis to smaller values of the crossover time. Using the superpositioned
data, the dynamic crossover can be observed in isochoric data, where it is
found that the relaxation time at the crossover for constant volume is
equivalent to the value obtained under (the more usual) condition of constant
pressure. Similarly, from the scaling analysis, isobaric relaxation times at
high pressure are deduced from experimental measurements at atmospheric
pressure. We find for all glass-formers studied, that the fragility (normalized
temperature dependence of tau or eta) is a decreasing function of pressure.
This conclusion is less subject to uncertainties in the measurements than
published determinations of the pressure coefficient of fragility. Finally, we
show that an empirical function, having the form of the Cohen-Grest relation
but without connection to any free volume model, parameterizes the master
curves, and accurately describes the data over all measured conditions.
