  Dielectric measurements of the alpha-relaxation time were carried out on a
mixture of ortho-terphenyl (OTP) with ortho-phenylphenol (OPP), over a range of
temperatures at two pressures, 0.1 and 28.8 MPa. These are the same conditions
for which heat capacity, thermal expansivity, and compressibility measurements
were reported by Takahara et al. [S. Takahara, M. Ishikawa, O. Yamamuro, and T.
Matsuo, Journal of Physical Chemistry B 103 (16), 3288 (1999).] for the same
mixture. From the combined dynamic and thermodynamic data, we determine that
density and temperature govern to an equivalent degree the variation of the
relaxation times with temperature. Over the measured range, the dependence of
the relaxation times on configurational entropy is in accord with the
Adam-Gibbs model, and this dependence is invariant to pressure. Consistent with
the implied connection between relaxation and thermodynamic properties, the
kinetic and thermodynamic fragilities are found to have the same pressure
independence. In comparing the relaxation properties of the mixture to those of
neat OTP, density effects are stronger in the former, perhaps suggestive of
less efficient packing.
