Osmotic pressure

Osmotic pressure - is the difference in pressure between two solutions that prevent fluid flow through semi-permeable membrane (Alberts, 2002). 

Osmotic pressure occurs when two solutions, separated by semipermeable membrane, have different concentrations of solutes, accordind to a rule of osmosis, fluid moves from the area of low concentration of solutes to an area of high concentration (Kent, 2000). 

Osmotic pressure can be calculated using the following formula (Alberts, 2002):

∏ = nRT/V = MMRT

Where:

n - the number of moles of solute present

R - ideal gas constant 

T - temperature in Kelvin

V - volume of the solution

MM - molar mass of the solute

References:

Alberts B, Johnson A, Lewis J, et al. (2002) Molecular Biology of the Cell. 4th edition. New York: Garland Science.

Kent, M. (2000) Advanced Biology. Oxford: Oxford University Press.