  We employ the adaptive resolution approach AdResS, in its recently developed
Grand Canonical-like version (GC-AdResS) [Wang et al. Phys.Rev.X 3, 011018
(2013)], to calculate the excess chemical potential, $\mu^{ex}$, of various
liquids and mixtures. We compare our results with those obtained from full
atomistic simulations using the technique of thermodynamic integration and show
a satisfactory agreement. In GC-AdResS the procedure to calculate $\mu^{ex}$
corresponds to the process of standard initial equilibration of the system;
this implies that, independently of the specific aim of the study, $\mu^{ex}$,
for each molecular species, is automatically calculated every time a GC-AdResS
simulation is performed.
