  We have carried out extensive low-temperature (1.5 to 10 K) measurements of
the critical field, $H_c$, for the element Pb up to a pressure of $P=1.2$ GPa.
  From this data the electronic entropy, specific heat, thermal expansion
coefficient and compressibility is calculated as a function of temperature,
pressure and magnetic field. The zero-field data is consistent with direct
thermodynamic measurements and the $P$-dependence of $T_c$ and specific heat
coefficient, $\gamma(T,P)$ allows the determination of the $P$-dependence of
the pairing interaction.
