In classical thermo, entropy has units of J/K. It's the gradient of the Helmholtz free energy w.r.t. temperature (at fixed volume). I think experimentally one g

In classical thermo, entropy has units of J/K. It's the gradient of the Helmholtz free energy w.r.t. temperature (at fixed volume). I think experimentally one generally measures the heat capacity as a function of temperature, from which you can obtain the entropy.