IUPAC Recommendations

TL;DR: IUPAC recommendations for Henry's law constants provide a consistent set of definitions and symbols for expressing proportionality coefficients. Two new recommended reciprocal quantities, Henry's law solubility constant (Hs) and Henry's law volatility constant (Hv), are defined.

Abstract: Henry’s law states that the abundance of a volatile solute dissolved in a liquid is proportional to its abundance in the gas phase. It applies at equilibrium and in the limit of infinite dilution of the solute. For historical reasons, numerous different definitions, names, and symbols are used in the literature to express the proportionality coefficient, denoted the “Henry’s law constant”. Here, a consistent set of recommendations is presented. An important distinction is made between two new recommended reciprocal quantities: “Henry’s law solubility constant” (Hs) and “Henry’s law volatility constant” (Hv). Eight recommended variants ofHs and Hv are described and relations among them presented.