An osmometer is a device for measuring the osmotic strength of a solution

Solution

In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

, colloid

Colloid

A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...

, or compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

.

There are several different techniques employed in osmometry:

• Vapor pressure depression osmometers determine the concentration of osmotically active particles that reduce the vapor pressure
  Vapor pressure
  Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...
  
   of a solution.
• Membrane osmometers measure the osmotic pressure
  Osmotic pressure
  Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....
  
   of a solution separated from pure solvent by a semipermeable membrane.
• Freezing point depression osmometer may also be used to determine the osmotic strength of a solution, as osmotically active compounds depress the freezing point
  Freezing Point
  Freezing Point is a news journal in the People's Republic of China which has been the subject of controversy over its criticism of Communist Party officials and the sympathetic ear it lent to a Chinese historian who had criticized official history textbooks...
  
   of a solution.

Osmometers are useful for determining the concentration of dissolved salts or sugars in blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 or urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 samples. Osmometry is also useful in determining the molecular weight of unknown compounds and polymers.

Osmometry is the measurement of the osmotic strength of a substance . This is often used by chemists for the determination of average molecular weight.