H4SiO4

H4SiO4 is the chemical formula for silicic acid. It is a general term that refers to any of the acids derived from silicon dioxide. The simplest form, orthosilicic acid, has the chemical formula Si(OH)4. In aqueous solution, silicic acid exists in a variety of polymeric forms, depending on the concentration of silicon and the pH. These polymers are often referred to as silica gels or colloids. Silicic acid is a weak acid. It is a common component of groundwater and is produced by the weathering of silicate minerals. In biological systems, silicic acid plays a role in the formation of silica structures in organisms like diatoms and sponges. The solubility of silicic acid in water is relatively low, and it tends to polymerize and precipitate out of solution as amorphous silica or hydrated silicon dioxide when its concentration exceeds a certain limit. This process is important in geological formations and in industrial applications such as the production of catalysts and desiccants.