Choosing and developing an extraction method

Henry's law constant

Henry's law constant reflects the volatility of a solute in aqueous solution.

It represents, at equilibrium, the partition coefficient of the solute between the aqueous solution and the gas phase:

Henry's law constant is expressed in atm.m³.mol^-1. The higher Henry's law constant, the more volatile the compound is – see K_H scale.

In the case of a dilute aqueous solution, Henry's law constant can be easily estimated from the values of the compound’s water solubility and vapor pressure:

$\LARGE K {_{H}} = \frac {Pv}{Sw}$

Scale of Kh (atm.m3.mol-1). Below 10 exp -7 : non volatile. From 10 exp -7 to 10 exp -5 : slightly volatile. From 10 exp -5 to 10 exp -3 : Moderately volatile. From 10 exp -3 to 10 exp -1 : Volatile. Above 10 exp -1 : Very volatile.