Clinical Application of Cryoscopy

Since 1888 when Beckmann¹devised the first relatively sensitive apparatus for determining the freezing point of a solution, the medical use of this instrument, the cryoscope or osmometer, has been limited mainly to physiological and clinical research for measuring total solute concentration and osmotic pressure. However, determination of the freezing point of biological fluids also has routine clinical value in assessing certain fluid, electrolyte, and urinary abnormalities. Osmotic Pressure When two aqueous solutions of different solute concentrations are separated by a semipermeable membrane, water molecules will move from one solution into the other. This movement is related to the average energy per unit concentration of the water molecules and is referred to as the "escaping tendency," or as the chemical potential. When the chemical potentials of the water molecules of two solutions differ, there will be a net movement of water molecules from the solution with the higher chemical potential