1. n. [Drilling Fluids]
A group of seven hydrated forms of SiO2, including the following silicic acids: tetra, H2Si4O9, meta-di, H2Si2O5, meta-tri, H4Si3O8, meta, H2SiO3, ortho-tri, H8Si3O10, ortho-di, H6Si2O7 and ortho, H4SiO4. The latter formula is often written as Si(OH)4. Silicic acids and silicate anions polymerize through formation of multiple Si-O-Si bonds. The polysilic structure can be linear or cyclic and is not uniform in size.