  We calculate the equation of state of dense hydrogen within the chemical
picture. Fluid variational theory is generalized for a multi-component system
of molecules, atoms, electrons, and protons. Chemical equilibrium is supposed
for the reactions dissociation and ionization. We identify the region of
thermodynamic instability which is related to the plasma phase transition. The
reflectivity is calculated along the Hugoniot curve and compared with
experimental results. The equation-of-state data is used to calculate the
pressure and temperature profiles for the interior of Jupiter.
