Osmometry is the measurement of the osmotic strength of a substance. This is often used by chemists for the determination of average molecular weight. Osmometers are useful for determining the concentration of dissolved salts or sugars in blood or urine samples. Osmometry is also useful in determining the molecular weight of unknown compounds and polymers.
Freezing point depression osmometer is used to determine the osmotic strength of a solution, as osmotically active compounds depress the freezing point of a solution. This type of osmometer is used for measuring the osmotic strength of a solution, colloid, or compound.
Freezing-point depression is also used to measure the degree of dissociation or the molar mass of the solute. This kind of measurement is called cryoscopy (Greek cryo = cold, scopos = observe "observe the cold") and relies on exact measurement of the freezing point. the procedure is primarily useful for organic compounds using a non-polar solvent.
Osmometers / Cryoscopes use super-cooled water phenomenon to measure the freezing point of liquids like milk, drugs etc.
Super cooling, also known as under cooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid. A liquid below its standard freezing point will crystallize in the presence of a seed crystal or nucleus around which a crystal structure can form creating a solid.
Watch: super cooled water explained!