Excess pressure required to maintain osmotic equilibrium between a solution and the
pure solvent separated by a
membrane permeable only to the solvent:
where
,
are the partial molar volume and activity of solvent
for an incompressible fluid. For ideal dilute solutions,
,
where entities
are individually moving solute molecules, ions, etc., regardless of their nature,
,
are the amount and mass concentration of the solutes, and
is the mass average molar mass of the solutes. The amount is sometimes expressed in
osmol (meaning a
mole of osmotically active entities), but this usage and the corresponding term
osmolarity are discouraged.
Source:
