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In chemistry, a silicic acid (/ s ɪ ˈ l ɪ s ɪ k /) is any chemical compound containing the element silicon attached to oxide (=O) and hydroxyl (−OH) groups, with the general formula [H 2x SiO x+2] n or, equivalently, [SiO x (OH) 4−2x] n. [1] [2] Orthosilicic acid is a representative example.
Orthosilicic acid (/ ˌ ɔːr θ ə s ɪ ˈ l ɪ s ɪ k /) is an inorganic compound with the formula Si(O H) 4. Although rarely observed, it is the key compound of silica and silicates and the precursor to other silicic acids [H 2x SiO x+2] n. Silicic acids play important roles in biomineralization and technology.
Hydrated silica is a form of silicon dioxide, which has a variable amount of water in the formula. When dissolved in water, it is usually known as silicic acid. It is found in nature as opal [2] (which has been mined as a gemstone for centuries), and in the cell walls of diatoms.
That would have been prepared in 1818 by Johann Nepomuk von Fuchs, by treating silicic acid with an alkali; the result being soluble in water, "but not affected by atmospheric changes". [8] The terms "water glass" and "soluble glass" were used by Leopold Wolff in 1846, [9] by Émile Kopp in 1857, [10] and by Hermann Krätzer in 1887. [11]
Many hydrates and silicic acids exist in the most dilute of aqueous solutions, but these are rather insoluble and quickly precipitate and condense and cross-link to form various polysilicic acids of variable combinations following the formula [SiO x (OH) 4−2x] n, similar to the behaviour of boron, aluminium, and iron, among other elements.
Here, the silicic acid H 4 SiO 4, or Si(OH) 4, which is equivalent to SiO 2 · 2 H 2 O represents hydrous or amorphous silica for the sake of simplicity in aqueous chemistry. Indeed, the term silicic acid has traditionally been used as a synonym for silica, SiO 2. Strictly speaking, silica is the anhydride of orthosilicic acid, Si(OH) 4.
Pyrosilicic acid is the chemical compound with formula H 6 Si 2 O 7 or (HO) 3 SiOSi(OH) 3. It is one of the silicic acids and has pyrosilicate as its conjugate base. It was synthesized, using nonaqueous solutions, in 2017. [1] H 6 Si 2 O 7 (aq) → 2 SiO 2 (s) + 3 H 2 O. Pyrosilicic acid may be present in sea water and other natural waters at ...
The production of sulfuric acid from anhydrous calcium sulfate produces calcium silicates. [9] Upon being mixed with shale or marl, and roasted at 1400 °C, the sulfate liberates sulfur dioxide gas, a precursor to sulfuric acid. The resulting calcium silicate is used in cement clinker production. [10] 2 CaSO 4 + 2 SiO 2 + C → 2 CaSiO 3 + 2 SO ...