Henry's law, formulated by William Henry in 1803, states "At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." Henry's law can be put into mathematical terms (at constant temperature) as p = kHc where p is the partial pressure of the solute in the gas above the solution, c is the concentration of the solute and kH is a constant with the dimensions of pressure divided by concentration. The constant, known as the Henry's law constant, depends on the solute, the solvent and the temperature.