Fugacity

03/14/2026

“How can we quantify how much a substance wants to escape from its mixture?”

Different substances have different levels of internal stability. Some very much want to escape their mixture, while others are happy where they are. So how can we quantify this? Well, scientists developed Fugacity theory to explain this phenomenon. Fugacity is defined as the empirically measured vapor pressure rather than the ideal vapor pressure. Chemicals will move between substances like air and water until their fugacity potentials are equal.