Pressure which must be applied to a solution to prevent water from flowing in via a semipermeable membrane.
Osmotic pressure depends on the total number of dissolved particles, so for a substance that dissociates into two ions, such as ordinary salt (sodium chloride), a one molar solution has an osmotic pressure of 2 osmoles.
Solutions with higher concentrations of dissolved substances are said to have higher osmotic pressure than solutions having lower concentrations; thus the solvent moves from an area of low osmotic pressure to an area of higher osmotic pressure.
|Human Blood Plasma||290mOsm|
Values are typically small and so quoted in milliosmoles (mOsm)