The synthetic route for producing of Silica gel (CAS NO.63231-67-4) was patented by chemistry professor Walter A. Patrick at Johns Hopkins University, Baltimore, Maryland in 1919. It was used in World War I for the absorption of vapors and gases in gas mask canisters, as part of his patent. The substance was in existence as early as the 1640s as a scientific curiosity.
In World War II, silica gel was indispensable in the war effort for keeping penicillin dry, protecting military equipment from moisture damage, as a fluid cracking catalyst for the production of high octane gasoline, and as a catalyst support for the manufacture of butadiene from ethanol, feedstock for the synthetic rubber program.
 

The Silica gel, with the CAS registry number 63231-67-4, is also known as Spherosil. Its classification code is TSCA UVCB. This chemical should be sealed and stored in a cool and dry place. Moreover, it should be protected from water, moisture and nitrogen fluoride. Silica gel is a granular, vitreous, highly porous form of silica made synthetically from sodium silicate. Silica gel is a solid and has a large specific surface area and strong mechanical strength, and it is a polarity adsorbent. Silica gel is non-toxic, non-flammable, and non-reactive and stable with ordinary usage. It is irritating to the respiratory tract and may cause irritation of the digestive tract, and dust from the beads may cause irritation to the skin and eyes, so precautions should be taken. It is a naturally occurring mineral that is purified and processed into either granular or beaded form. As a desiccant, it has an average pore size of 2.4 nanometers and has a strong affinity for water molecules. It may be used to keep the relative humidity inside a high frequency radio or satellite transmission system waveguide as low as possible. Silica gel is also used to dry the air in industrial compressed air systems. It is used in chromatography as a stationary phase. What's more, it is an adsorbent for aromatics and has found use in extracting aromatics from refinery streams. 

Preparation: a solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel. When a visible indication of the moisture content of the silica gel is required, ammonium tetrachlorocobaltate(II) (NH₄)₂CoCl₄ or cobalt chloride CoCl₂ is added. This will cause the gel to be blue when dry and pink when hydrated. An alternative indicator is methyl violet which is orange when dry and green when hydrated.