Quantity of solutes per liter of solution, which contributes to the pressure of that solution on a membrane.
Osmolality is the concentration of particles in a solution and determines the pressure that is exerted across a membrane. Osmolality is expressed as the moles of a solute per kilogram of solvent. Osmolarity also describes the particles in a solution, but is expressed in terms of liters of solution rather than by weight.
Concentration of dissolved substances per kilogram of solvent (often water). The term tonicity is used to describe the osmolality of a solution relative to plasma. Solutions with the same osmolality as plasma are considered isotonic; those with greater osmolality are hypertonic, and those with lower osmolality are hypotonic. Tonicity and osmolality are important considerations medically, particularly in determining the type of intravenous fluid to give a patient. Normal saline (0.9% sodium chloride solution) is isotonic to plasma while dextrose in water solutions (D5W) are hypotonic. When given in excess, hypo¬ tonic solutions, such as D5W, may abnormally dilute plasma concentrations of sodium and potassium, resulting in harm to the patient. Compare to osmolarity, which is the concentration of dissolved substance per liter of solution (such as plasma). Osmolarity is affected by the volume of the various solutes in the solution and the temperature, while osmolality is not.
Osmotic concentration; the characteristic of a solution determined by the ionic concentration of the dissolved substances per unit of solvent.
A quantification of the ratio between the amount of solute and the volume of solvent within a solution.