Osmometry is the measurement of the osmotic strength of a solution, colloid, or compound. There are a wide variety of osmometers that may be used for this purpose: vapor pressure, freezing point depression, or membrane osmometry are the most common.
In vapor pressure osmometry, the osmometer determines the concentration of osmotically active particles that may reduce a solutionís vapor pressure. Large numbers of particles depress pressure. Similarly, large quantities of solute depress the freezing point of a solvent; in the case of water, salt depresses its freezing point to zero degrees Fahrenheit.
Membrane osmometry separates the solvent from the polymer solution with a semipermeable membrane, held tightly between two chambers. The flow from solvent to polymer is measured to determine the osmotic strength. When pressure is reduced on the solvent side, this tendency is reduce; when the two pressures are in equilibrium, the pressure on the solvent side can be measure to determine osmotic pressure.
Using osmometry, physicians can measure dissolved salts and sugars in blood and urine samples, diagnosing a variety of diseases. Scientists also use it to measure molecular weight of an unknown compound.
Web Resources On Osmometry
Vapor Pressure Osmometer
Measurement of Osmolality
Book Resources On Osmometry
Rapid osmometry with diffusable polymers by Peter M Holleran
Elasto-osmometry by Jacob van Dam