Dissolution is the process where one chemical substance forms a solution with another: molecules of the two substances exist mingled in a single continuous phase. The majority component is called the solvent and the minority component is called the solute. Prior to dissolution, the solvent and the solute are often different phases (i.e. carbon dioxide gas or solid salt dissolving in the solvent water). There are various applications of dissolution associated with CDR.

Probably the most relevant dissolution is carbon dioxide in water. When water is in contact with gas containing CO2, some CO2 will become “aqueous”. The maximum amount that can dissolve is described by Henry’s Law - that says a concentration of dissolved gas is equal to a constant multiplied by the partial pressure of the gas. The partial pressure of a gas is the portion of the total gas pressure that is exerted by the subject fraction. For example, if a mixture of two gases in equal amounts is at one atmosphere of pressure, each gas is said to contribute half of the total pressure - each gas has a partial pressure of 0.5 atm.

The proportionality constant for relating partial pressure to solution concentration is called the Henry’s Law constant. For CO2 dissolving in water at 25C, KH = 0.034 mole/(kg-bar). In other words, CO2 will dissolve in water with a maximum concentration of 0.034 mole/kg (or per liter, since the density of water is one kg/L), if the water is in contact with CO2 gas with a partial pressure of one bar. At lower temperature, more gas can dissolve. For water at 0C, KH = 0.071 mole/(kg-bar).

After carbon dioxide has dissolved into water, it can undergo chemical reaction with water molecules and take other forms.
{aspects for discussion: partial pressure and fugacity, solubility, Henry’s Law, diffusion and other mass-transport phenomena, boundary layers and turbulence}