An equilibrium is established between the two processes when, per unit of time, just as many CO 2 molecules migrate from the air into the water as migrate in the opposite direction from the water into the air. In this way, the corresponding equilibrium concentrations are established in the air and in the water, which correspond to the existing physical conditions (e.g. temperature, pressure). Solubility can be described by the partition coefficient K or the BUNSEN absorption coefficient α. Solubility in water depends on temperature and partial pressure of CO 2 in air. The BUNSEN absorption coefficient α is about 1.2 for CO 2 , which means that at equilibrium with air, the concentration in water is about 1.2 times. This in turn means that CO 2 dissolves very well in water (For comparison O 2 : α = 0.38).