The pressure which a solution of a substance in a liquid exerts on a semipermeable membrane, through which the solvent can diffuse but the dissolved substance (the solute) cannot diffuse, when separated across the membrane from the pure solvent. In general, the osmotic pressure will depend almost proportionally up to certain concentrations upon the molal concentration of the solute.
A chemical force caused by a concentration gradient. It is a colligative property and the principle behind membrane processing.
Osmotic pressure () is the excess pressure necessary to maintain osmotic equilibrium between a solution and the pure solvent separated by a membrane permeable only to the solvent. In an ideal dilute solution Î = c RT where B is the amount-of-substance concentration of the solute, is the molar gas constant, and the temperature.