In chemistry, the osmole (Osm) is a non-SI unit of measurement that defines the number of moles of a chemical compound that contribute to a solution's osmotic pressure.

Osmolarity is a measure of the osmoles of solute per litre of solution, while the osmolality is a measure of the osmoles of solute per kilogram of solvent. If the concentration is very low, osmolarity and osmolality are considered equivalent. In calculations for these two measurements, salts are presumed to dissociate into their component ions. For example, a mole of glucose in solution is one osmole, whereas a mole of sodium chloride in solution is two osmoles (one mole of sodium and one mole of chloride). Both sodium and chloride ions affect the osmotic pressure of the solution.

Chemical properties | Units of amount of substance

See also

• Molarity
• Molality
• Plasma osmolality

External link

• MedlinePlus Medical Encyclopedia

Osmolarität | Osmolalité | Osmolariteit | Osmoli