Foreword
15
Osmo1® Single-Sample Micro-Osmometer User Guide
Non-ionic solution
Certain molecules, when dissolved, do not dissociate or ionize into charged particles. Good examples are glucose and
urea.
Osmol (or Osmole)
The standard unit of osmolality based on a one molal concentration of an ion in a solution.
Osmolality
The number of osmoles of solute per kilogram of solvent (temperature independent).
Osmolality equation
Osmolality is the number of osmoles of solute particles per kilogram of pure solvent. Since most ionic species do not
completely dissociate, osmolality is a unit of concentration, which must take into account the dissociative eect.
Osmolality is usually expressed in mOsm/kg H₂O. One milliosmole (mOsm) is 10
-3
osmoles. The osmolality equation is:
Osmolality = ϕnC = osmole / kg H₂O
where:
ϕ = osmotic coecient, which accounts for the degree of molecular dissociation
n = number of particles into which a molecule can dissociate
C = molal concentration of the solution
Osmolarity
The number of osmoles of solute per liter of solution (temperature dependent).
Osmotic pressure
The hydrostatic pressure produced by a dierence in concentration between solutions on two sides of a surface such
as a semi-permeable membrane.
Solutes
The minor components of a solution which is dissolved into the solvent.
Solutions
The homogeneous mixture of solutes in a solvent.
Solvent
The major liquid component of a solution and the substance into which a solute is dissolved.
Vapor pressure osmometers
Instruments which measure the concentration of osmotically active particles which reduce the vapor pressure of the
solution.
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