Pyrosilicic acid is the chemical compound with formula H₆Si₂O₇ or (HO)₃SiOSi(OH)₃. It is one of the silicic acids and has pyrosilicate as its conjugate base.

Pyrosilicic acid

Names
IUPAC name Trihydroxysilyl trihydrogen orthosilicate
Other names disilicic acid
Identifiers
CAS Number	20638-18-0 N
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29292 Y
ChemSpider	55684 Y
Gmelin Reference	26937
PubChem CID	61804
InChI InChI=1S/H6O7Si2/c1-8(2,3)7-9(4,5)6/h1-6H Y Key: KDJOAYSYCXTQGG-UHFFFAOYSA-N Y
SMILES O[Si](O)(O)O[Si](O)(O)O
Properties
Chemical formula	H6O7Si2
Molar mass	174.211 g·mol−1
Conjugate base	Pyrosilicate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N (what is YN ?) Infobox references

It was synthesized, using nonaqueous solutions, in 2017.^[1]

${\displaystyle {\ce {H6Si2O7(aq) -> 2 SiO2(s) + 3 H2O}}}$

Pyrosilicic acid may be present in sea water and other natural waters at very low concentration.^[2][3] Compounds formally derived from it, such as sodium pyrosilicate, are found in the sorosilicate minerals.