Silicic acid /sɪˈlɪsɪk ˌæsɪd/ is a chemical compound. It is a silanol.
Silicic acid is the general name for a family of chemical compounds containing
the element silicon attached to oxide and hydroxyl groups. This family of
compounds have the general formula [SiOx(OH)4-2x]n. Some simple silicic
acids have been identified, but only in very dilute aqueous solution, such as
metasilicic acid, orthosilicic acid, disilicic acid, and pyrosilicic acid;
however in the solid state these probably condense to form polymeric
silicic acids of complex structure. Chemical reactions
In general, silicic acid reactions are difficult to control. Partial
dehydration to metasilicic acid, for example, is challenging because the
reaction typically progresses all the way to silicon dioxide and water.
= Acid-base reactions= Like other silanols, silicic acid is a
weak acid. It can be deprotonated in solution, the conjugate base silicate is
known. Production
Silicic acid was discovered by Jöns Jacob Berzelius between 1810 and 1836
when studying silicon generated by his experiments. However, he failed to
recognise it as distinct from silicon dioxide.
= Hydration= Naturally occurring silicic acid is
produced by a non-biological process called hydration involving water, and
quartz, which is known to be common on Earth. The reaction producing silicic
acid from quartz can be written as: Quartz + Water → Silicic acid, or: SiO
2 + 2 H 2O → H
4SiO 4.
= Laboratory synthesis= Silicic acid can be produced by the
acidification of sodium silicate in aqueous solution. The main problem in
using silicic acids in chemical synthesis is that silicic acids readily
lose water to form randomly polymeric silica gel, a form of silicon dioxide.
Such conversion involve condensations. Oceanic silicic acid
Silicic acid is created near the ocean's surface, by the process of hydration. It
is carried into the abyssopelagic zone by falling water in the poles.
Uncontrolled build-up of silicic acid in the ocean is naturally checked –
although human influence can upset this natural regulation. It is primarily
removed by conversion to silicon dioxide and water. In the oceans, silicon exists
primarily as orthosilicic acid, and its biogeochemical cycle is regulated by the
group of algae known as the diatoms. These algae polymerise the silicic acid
to so-called biogenic silica, used to construct their cell walls.
Silicic acid in health Continuing research of the correlation
of aluminium and Alzheimer's disease has in the last few years included the use
of silicic acid in beverages, due to its abilities to both reduce aluminium
uptake in the digestive system as well as cause renal excretion of aluminium.
Study has shown that physiological concentration of orthosilicic acid
stimulates collagen type 1 synthesis and osteoblastic differentiation in human
osteoblast-like cells in vitro. Choline-stabilized orthosilicic acid is
a bioavailable nutritional supplement. It has been shown to prevent the loss of
hair tensile strength, have positive effect on skin surface and skin
mechanical properties, and on brittleness of hair and nails, abate
brittle nail syndrome, partially prevent femoral bone loss in the aged
ovariectomized rat model, increase collagen concentration in calves , and
have potential beneficial effect on bone collagen formation in osteopenic
females. References
External links Bioinorganic Chemistry of Aluminium and
Silicon research group website