Osmotic pressure is the phenomenon of water flow through a semi-permeable membrane that blocks the transport of salts or other solutes. Osmosis is applied to water purification and desalination, waste material treatment, and many other chemical and biochemical laboratory and industrial processes.
The Osmotic pressure calculation formula is:
  π = i . Φ * c . R. T
Where:
π: Osmotic pressure
i: Number of ions produced by solute dissiation, e.g. 2 of NaCl, 3 of MgCl₂
Φ: Osmotic coeffient
c: Concentration of the solution
R: Universal gas constant, 0.083145 Liter.bar/(deg.mol)
T: Absolute temperature, in K