  Since its initial discovery more than fifteen years ago, the thermodynamical
scaling of the dynamics of supercooled liquids has been used to provide many
new important insights in the physics of liquids, particularly on the link
between dynamics and intermolecular potential. A question that has long been
discussed is whether the scaling exponent gamma is a constant or it depends on
pressure. Here we offer a simple method to determine the pressure dependence of
gamma using only the pressure dependence of the glass transition and the
equation of state. Using this new method we find that for the six
non-associated liquids investigated gamma always decreases with increasing
pressure. Importantly in all cases the value of gammaremains always larger than
4. Liquids having gamma closer to 4 at low pressure show a smaller change in
gamma with pressure. We argue that this result has very important consequences
for the experimental determination of the functional form of the repulsive part
of the potential in liquids.
