PHYSICAL CHEMISTRY PROPERTIES OF MATTER A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site osmosis The principle of osmosis. The osmotic pressure difference across a semipermeable membrane separating two solutions of different concentrations causes transport of the solvent through the membrane tending to equalize the concentrations of the two solutions. The process continues until an equilibrium state is achieved, either equal concentrations, or, in this case, balance between the osmotic pressure difference and the hydrostatic pressure excess of the solution in the inverted thistle funnel. The hydrostatic pressure difference thus provides a measure of the osmotic pressure difference. The diffusion of a solvent, such as water, through a semipermeable membrane that separates two solutions of different concentration, the movement being from the more dilute to the more concentrated solution, owing to the thermodynamic tendency to equalize the concentrations. The liquid flow may be opposed by applying pressure to the more concentrated solution: the pressure required to reduce the flow to zero from a pure solvent to a given solution is known as the osmotic pressure of the solution. Osmosis was studied by Thomas Graham, who coined the term (1858); in 1886 Van't Hoff showed that, for dilute solutions (obeying Henry's law), the osmotic pressure varies with temperature and concentration as if the solute were a gas occupying the volume of the solution. This enables molecular weights to be calculated from osmotic pressure measurements, and degrees of ionic dissociation to be estimated. Osmosis is important in dialysis and in water transport in living tissues. Related categories    • PHYSICAL CHEMISTRY    • PROPERTIES OF MATTER Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP