For an ideally polarizable electrode it is found that among numerous v
olume Hansen excesses there exists one which is correlated with the Ar
chimedes law and plays the role of the solution volume displaced due t
o occurrence of surface layer. This volume excess could be called the
Archimedes volume excess or the Archimedes volume of the surface. The
Archimedes volume of the surface can be expressed in the form of a par
tial thermodynamic derivative