text: A low concentration solution is created by adding a small amount of polymer to a solvent. This solution is separated from pure solvent by a semipermeable membrane. Solute cannot cross the semipermeable membrane but the solvent is able to cross the membrane. Solvent flows across the membrane to dilute the solution. The pressure required to stop the flow across the membrane is called the osmotic pressure. The osmotic pressure is measured and used to calculate .
  In an ideally dilute solution, van ‘t Hoff's law of osmotic pressure can be used to calculate  from osmotic pressure.
  , number average molecular weight, mass/mole
  , gas constant
  , absolute temperature, typically Kelvin
  , concentration of polymer, mass/volume
  , osmotic pressure