The pressure that must be applied to a solution to prevent osmosis through a semi-permeable membrane. Given by π = MRT (van't Hoff equation), where M is molar concentration and T is temperature. Used to measure molar mass of large molecules and in water purification (reverse osmosis).
Osmotic pressure (Π) is the pressure that must be applied to a solution to prevent osmosis (the flow of solvent from pure solvent through a semipermeable membrane into the solution). It is a colligative property: Π = iMRT, where i is the van't Hoff factor, M is molarity, R = 8.314 J/mol·K, T is absolute temperature. High solute concentrations produce high osmotic pressures. Blood plasma osmotic pressure ≈ 7.7 atm at 37°C.
Uses & Applications
Osmotic pressure is applied in: desalination (reverse osmosis, where pressure exceeding Π forces water through membrane against osmosis), pharmaceutical IV solution design (isotonic solutions at 0.9% NaCl or 5% glucose to match blood osmotic pressure), membrane osmometry (measuring polymer molar masses), cell biology (osmotic stress causes cell shrinkage or lysis), and food preservation (high sugar/salt concentrations create osmotic pressure that dehydrates microorganisms).
Safety Information
Intravenous solutions must be carefully isotonic: hypotonic solutions cause red blood cell lysis (haemolysis); hypertonic solutions cause crenation (cell shrinkage). Rapid shifts in plasma osmolality (hypernatraemia correction too fast) can cause dangerous central pontine myelinolysis. Reverse osmosis membranes under high pressure require pressure-rated equipment and relief valves.
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
The pressure that must be applied to a solution to prevent osmosis through a semi-permeable membrane. Given by π = MRT (van't Hoff equation), where M is molar concentration and T is temperature. Used to measure molar mass of large molecules and in water purification (reverse osmosis).
Osmotic pressure is applied in: desalination (reverse osmosis, where pressure exceeding Π forces water through membrane against osmosis), pharmaceutical IV solution design (isotonic solutions at 0.9% NaCl or 5% glucose to match blood osmotic pressure), membrane osmometry (measuring polymer molar mas…
Intravenous solutions must be carefully isotonic: hypotonic solutions cause red blood cell lysis (haemolysis); hypertonic solutions cause crenation (cell shrinkage). Rapid shifts in plasma osmolality (hypernatraemia correction too fast) can cause dangerous central pontine myelinolysis. Reverse osmos…
The formula or notation for Osmotic Pressure is: Π = MRT (van't Hoff); Π = cRT for ideal dilute solution
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and IAEA. For educational purposes only — always consult official SDS documentation and qualified
professionals before handling chemicals.
