MC simulation in the semigrand canonical ensemble requires the calibration of the chemical potential ∆µ used as a thermodynamic parameter governing the osmostat in equilibrium with an infinitely sized reservoir of electrolyte at a specified salt concentration. We invite the readers to refer to the original publication of Ross and Chodera for more details. In their work, the self-adjusted mixture sampling sample uniformly salt concentration during a single simulation, follow by application of the Bennett acceptance ratio to extract relevant free energy difference from NCMC move. The chemical potential can be thus extracted from relation between macroscopic electrolyte concentration and free energies.