partial pressure (quality) Green Book, 2nd ed.: IUPAC Quantities, Units and Symbols in Physical Chemistry. Second Edition, Blackwell Scientific Publications, Oxford, 1993. partial pressure (quality) PAC, 1994, 66, 533 (Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994)) partial pressure Partial pressure is the notional pressure of a gas in a mixture of gases, if it alone occupied the entire volume of the original mixture at the same temperature. [Wikipedia] pressure (quality)