  We report the first measurements of equations of state of a fully relaxed
magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma,
called Taylor states, are formed in a coaxial magnetized plasma gun, and are
allowed to relax and drift into a closed flux conserving volume. Density, ion
temperature, and magnetic field are measured as a function of time as the
Taylor states compress and heat. The theoretically predicted MHD and double
adiabatic equations of state are compared to experimental measurements. We find
that the MHD equation of state is inconsistent with our data.
