Which measurement principle is applied in a vapor pressure osmometer?

A vapor pressure osmometer measures osmolality by utilizing the principle of vapor pressure depression. When a solute is added to a solvent, the vapor pressure of the solvent is reduced; this phenomenon is directly related to the concentration of the solute particles in the solution. The Seebeck principle, which pertains to thermoelectric effects and temperature differences creating voltage, does not apply to vapor pressure osmometers as they do not measure temperature differences in the same manner.

In the context of the question, the correct answer aligns with the relevant scientific principles governing vapor pressure and solution behavior, while the other measurement principles listed focus on different physical phenomena. This specificity helps in understanding that a vapor pressure osmometer operates fundamentally on vapor pressure changes due to solute interactions, rather than thermoelectric effects or unrelated measurement techniques.