The Semi-Micro Osmometer K-7400 measures the freezing point depression of liquids and it is based on the succesful predecessor model Type Dig. L The principle of total osmolality is to determine the osmolality of body fluids such as blood (serum) and urine. This is an essential routine process in clinics*, institutes, and universities. Osmolality describes the concentration of osmotic effective particles in solutions, independent from type, composition or electrical charge. The osmolality refers to the mass of the solution, meaning 1 kg of pure water.