Note 8 — Chapter II · THE CHEMICAL PROCESSES OF SOIL FORMATION.
Reading edition
Owing to the universal presence of water (H₂O) in air as well as in soils, it is usual and convenient to speak of carbonic dioxid (CO₂) gas when so occurring as carbonic acid (H₂CO₃), of which it produces the effects (CO₂ + H₂O = H₂CO₃).