For calcium containing mineral such as silicates (e.g., CaSiO3) the carbonation is facilitated by the presence formation of carbonic acid (H2CO3), formed by the dissolution of carbon dioxide in water . Carbonic acid is a weak acid since its ionization in water is incomplete, but it reacts with calcium silicates to liberate calcium ions that react further with carbonate: Thus, a high carbonic acid concentration is required to increase the carbonation reaction. The hydration equilibrium constant of carbonic acid is, at 25 °C: