Henry's Law

A formula for Henry's Law is:

where:

is approximately 2.7182818, the base of the natural logarithm (also called Euler's number)

is the partial pressure of the solute above the solution

is the concentration of the solute in the solution (in one of its many units)

is the Henry's Law constant, which has units such as L·atm/mol, atm/(mol fraction) or Pa·m³/mol.

Taking the natural logarithm of the formula, gives us the more commonly used formula:

Some values for k include:

oxygen (O₂) : 769.2 L·atm/mol

carbon dioxide (CO₂) : 29.4 L·atm/mol

hydrogen (H₂) : 1282.1 L·atm/mol

when these gases are dissolved in water at 298 kelvin.

Note that in the above, the unit of concentration was chosen to be molarity. Hence the dimensional units: L is liters of solution, atm is the partial pressure of the gaseous solute above the solution (in atmospheres of absolute pressure), and mol is the moles of the gaseous solute in the solution. Also note that the Henry's Law constant, k, varies with the solvent and the temperature.