SILICIC ACID: PROPERTIES, REACTIONS AND USES - CHEMISTRY - 2025

The silicic acid is a hydrated form of silicon oxide. It is the general name for the family of chemical compounds made up of silicon, and a certain amount of hydrogen and oxygen molecules.

The general formula of these acids is _n, and the most common form in which it is usually found is that of orthosilicic acid H ₄ SiO ₄.

Figure 1: Structure of silicic acid.

Silicic acid is part of the Miscellaneous Silicates family. This means that the largest metallic oxoanion is the silicate, and that no non-metallic atom is attached to it. There are some isolated cases where they have one non-metallic atom, but never more than one.

Silicic acid physical properties

Silicic acid only exists in two states, amorphous and crystalline. The first is obtained by a precipitation process and the second is presented as rock crystal.

Silicic acid in its amorphous form (SiO ₃) is white, tasteless, insoluble in water and does not form any cohesive plastic mass with its molecules as occurs with aluminum.

In its crystalline state, it is not dissolved by any oxacid. When a very dilute solution of silica solution is treated with sulfuric, nitric or hydrochloric acid, the silicic acid is not precipitated. Instead, it appears to be dissolved in water as a hydrate.

When a solution of the acid or acid is added to a silicate solution, the hydrate is precipitated in a gelatinous form which when dried and subsequently heated with great energy becomes an insoluble substance.

Chemical reactions

Silicic acid is extremely weak and only loses its first proton as it approaches pH 10. Only 3 known reactions with this acid occur under normal physiological conditions of life.

1. Reaction with itself when solubility is exceeded to form amorphous silica hydrate.
2. Its reaction with aluminum hydroxide to form aluminum silicate hydroxide.
3. Reaction with excess molybdate to form heteropolyacids such as silicomolybdate.

Where is silicic acid found?

After oxygen, silicon is the most common element in nature, it is in the form of crystals. When in aqueous medium it becomes non-ionizing, so the silicon salts in the ocean can acidify the silicon and create silicic acid.

The net inputs of silicic acid in the world ocean have been found at 6.1 ± 2.0 teramoles of silicon per year (1 teramol = 1012 moles). Almost 80% of this contribution comes from rivers whose global average concentration is 150 micromolar (concentration in water).

In modern marine sediments, the net yields of biogenic silicon (transformation of dissolved silicate into particulate skeletal material) is 7.1 ± 1.8 teramoles per year.

The gross production of biogenic silica in surface waters is 240 ± 40 teramoles of silicon per year, and the preservation ratio (accumulation of opales in sediments / gross production in surface waters) is 3 percent.

In the flora it can be found in the Borago officinalis (Borraje) plant, which in its composition contains up to 2.2% silicic acid.

Orthosilicic acid is the most common form of silicic acid, which can be found in many different places. The largest bioavailable sources of this acid are found in water, whether in seawater or other beverages such as beer.

To obtain it in the laboratory, it follows the same principle as in the ocean, it can be obtained by acidifying sodium silicate in an aqueous solution.

Uses in everyday life

Toothpaste

It is the abrasive gel used in toothpaste, or in the clear part of scratched toothpaste, since in combination with calcium carbonate, it helps to safely remove plaque with brushing.

It is registered as a safe compound with the United States Food & Drug Administration and has no known toxicity or carcinogenicity.

Desiccant

When dried in an oven, it loses water and becomes a desiccant (a substance that draws water from the air). Therefore, small packets of silica gel crystals can be found in containers whose contents can be damaged by moisture such as vitamin bottles, electronics, shoes, or leather products.

Other uses

It can be found in gift shops such as magic stones, chemical garden, or crystal garden. Its dry form is mixed with salts of different metals.

When sodium is thrown into the water it is replaced by the metal and since the metal silicate is not soluble in water, a precipitate of the characteristic color of the metal forms. Metal silicate also expands as a gel and grows as colorful stalagmites in water.

Orthosilicic Acid (OSA) Medical Benefits

Orthosilicic acid is the best bioavailable silicon medium for humans. It can be used to treat various health conditions such as Alzheimer's disease, arthritis, atherosclerosis, hypertension, heart disease, osteoporosis, stroke, and hair.

Bone health

In a 2008 study of 136 women with osteopenia, they were given orthosilicic acid along with calcium and vitamin D or a placebo every day for a year. After one year, the participants who received the acid improved in bone formation.

Scientists say this is due to orthosilicic acid's ability to stimulate the production of collagen (a protein found in connective tissue) and to promote the development of bone-building cells.

Hair health

A small study published in 2007 suggests that this acid can help improve hair quality and health. In the study, 48 women with "fine hair" were divided into two groups and given a placebo or orthosilicon supplement for nine months.

Researchers found that orthosalicylic acid appeared to increase hair strength and thickness. In general, hair quality has also been improved with orthosalicylic acid supplementation.

References

1. National Center for Biotechnology Information. PubChem Compound Database; CID = 14942. Recovered from: pubchem.ncbi.nlm.nih.gov.
2. Graham, T. (1863). On the Properties of Silicic Acid and other Analogous Colloidal Substances. Proceedings of the Royal Society of London, 13, 335-341. Recovered from: jstor.org.
3. The Editors of Encyclopedia Britannica (1998) Silicic Acid Chemical Compound. Encyclopedia Britannica. Recovered from: britannica.com.
4. Tomsofmaine.com. (2017). Hydrated Silica - Tom's of Maine. Recovered from: tomsofmaine.com.
5. William Thomas Brande, Alfred Swaine Taylor. Chemistry. Blanchard and Lea. Retrieved on March 21, 2017 from books.google.co.ve.id.
6. Field, S. (2017). Hydrated silica. Retrieved on March 22, 2017 from: sci-toys.com.