SILICA GEL

Silica Gel is sometimes used in laboratory processes, for example to suppress convection in liquids or prevent settling of suspended particles.
Silica gel is sometimes used as a preservation tool to control relative humidity in museum and library exhibitions and storage.
Silica gel is also used to dry the air in industrial compressed air systems.

CAS Number: 112926-00-8 
1343-98-2 (Silicic acid) 
Chemical formula: SiO2
Molar mass: 60.08 g/mol

SYNONYMS:
Silica gel, Silicon dioxide, Amorphous silica, Precipitated silica, Synthetic amorphous silica, Silica xerogel, Silicic anhydride, CAB-O-SIL, Aerosil, Ludox, Santocel, Silica xerogel, silica hydrogel, amorphous silica, precipitated silica, silicic acid anhydride, silicic oxide, kieselgel, desiccant silica gel, porous silica, Silica gel, Silicon dioxide, Amorphous silica, Precipitated silica, Synthetic amorphous silica, Silica xerogel, Silicic anhydride, CAB-O-SIL, Aerosil, Ludox, Santocel

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular three-dimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.
The voids may contain water or some other liquids, or may be filled by gas or vacuum.

In the last case, Silica Gel is properly called silica xerogel.
Silica Gel is hard and translucent, but considerably softer than massive silica glass or quartz, and remains hard when saturated with water.
"Wet" silica gel, as may be freshly prepared from alkali silicate solutions, may vary in consistency from a soft transparent gel, similar to gelatin or agar, to a hard solid, namely a water-logged xerogel.

Silica gel is a moisturizing agent that absorbs excess water and eliminates unpleasant odors, and it's also used in cat litter.
For the same reason, Silica Gel can be used to prevent unpleasant odors in our gym bags.
Silica gel provides a much more effective and practical drying solution for electronic devices exposed to liquids than the commonly known rice method.

Another broad application for silica gel packaging is transportation and storage.
Desiccant silica gel packaging is one of the most common and effective methods for garment storage and transportation, particularly in the apparel industry, as it absorbs moisture and prevents odor formation.

For the same reason, silica gel is also used in shoe boxes, providing complete protection during transportation or storage if the product box becomes wet due to rain or other leaks, or if it is stored in a damp location.
Silica Gel is a synthetic, porous, and granular form of silicon dioxide (SiO₂) produced by polymerizing sodium silicate into a hard, glass-like material and then granulating it into beads or irregular particles.

Despite its name, Silica Gel  is not a "gel" but a rigid solid with a highly porous structure, providing a very large internal surface area (typically 300–1000 m²/g).
Its unique network of interconnected pores allows Silica Gel to adsorb and retain significant amounts of moisture, which makes it one of the most effective and widely used desiccants (drying agents) in various industries.

Silica gel is commonly described as a way to remove moisture from phones and electronics accidentally exposed to water, but there are no known controlled studies that compare its actual efficacy compared to simple air or fan exposure.

USES and APPLICATIONS of SILICA GEL:
Food Industry: Silica Gel extends shelf life of packaged dry foods like nuts, snacks, and spices.
Silica Gel has versatile industrial and commercial applications due to its strong adsorption capacity and inert chemical nature.
Silica Gel is sometimes used in laboratory processes, for example to suppress convection in liquids or prevent settling of suspended particles.

Silica Gel is used desiccant.
Silica gel help by absorbing moisture and extending the life of these items.
Silica gel may also be used to keep the relative humidity inside a high frequency radio or satellite transmission system waveguide as low as possible.

Silica Gel is common for a small compressed air system (similar to a small home aquarium pump) to be employed to circulate the air inside the waveguide over a jar of silica gel.
Silica gel is also used to dry the air in industrial compressed air systems.

Air from the compressor discharge flows through a bed of silica gel beads.
The silica gel adsorbs moisture from the air, preventing damage at the point of use of the compressed air due to condensation or moisture.
The same system is used to dry the compressed air on railway locomotives, where condensation and ice in the brake air pipes can lead to brake failure.

Prior to widespread use of air-conditioning, salt shakers with caps containing silica gel beads to keep the salt dry enough to prevent clumping were marketed in the US, replacing the practice of including a few grains of rice in salt shakers to effect the same drying.
Silica gel is sometimes used as a preservation tool to control relative humidity in museum and library exhibitions and storage.
Other applications of Silica Gel include diagnostic test strips, inhalation devices, syringes, drug test kits, and hospital sanitation kits.

-Moisture Control & Preservation uses of Silica Gel:
Silica Gel is used in packaging (electronics, leather goods, pharmaceuticals, foods, clothing, optics) to prevent moisture damage.
Silica Gel prevents mold, corrosion, spoilage, and degradation.

-Pharmaceuticals & Healthcare uses of Silica Gel:
Silica Gel protects drugs, capsules, and vitamins from humidity.
Silica Gel is used in diagnostic kits to maintain reagent stability.

-Industrial Applications of Silica Gel:
Silica Gel is used in compressed air and gas drying systems.
Silica Gel functions as a chromatography medium in laboratories.
Silica Gel is applied in transformer and power equipment drying.

-Consumer Goods uses of Silica Gel:
Silica Gel is found in shoeboxes, handbags, electronics packaging, and optical instruments.
Silica Gel is used to keep photographic equipment and hearing aids dry.

-Specialized Applications of Silica Gel:
Catalyst support in petrochemical industry.
Adsorbent in chromatography (TLC, column chromatography).
Humidity buffering in museums and archives.

WHAT IS SILICA GEL AND HOW IS SILICA GEL USED?
Silica gel is widely used in daily life and many industrial areas to prevent problems caused by excessive moisture.
Due to its effective absorption properties and affordable price, silica gel is a popular choice for many manufacturers worldwide, particularly in the food packaging industry.

Silica Gel is used to absorb moisture and keep items dry.
Silica Gel also has a wide variety of uses in people's daily lives.

Silica gel is a silicon dioxide with a high water adsorption capacity under pressure and a large pore size.
This structure allows Silica Gel to retain more than 40% of its own weight in moisture.

Silica Gel is now widely used in many areas because it removes moisture from the environment inside the packaging, extending the shelf life of products and preventing many problems caused by excess moisture, such as corrosion, mold, and rust.

Silica gel has long been an integral part of people's personal and daily lives, even if they are not aware of it.
There are many uses for preventing excess moisture and its many negative effects.

Many manufacturers add these desiccant packets to their products to ensure their products reach consumers fresh and dry, but in reality, silica gel packets serve much more than just personal purposes.

Silica gel is arguably the most efficient and cost-effective way to protect products from excessive moisture and spoilage.
Silica Gel's a highly effective desiccant for electronics, vitamins, leather goods, dried meats, and anything else that needs to be kept dry.

These desiccants, which absorb and retain moisture, are environmentally friendly, offering a long shelf life and low cost, while also ensuring their waste doesn't pollute the environment.

The versatile silica gel packaging is an adsorbent and acidic material.
Therefore, Silica Gel can also absorb impurities found in items you want to purify and separate.

WHAT IS SILICA GEL AND WHAT IS SILICA GEL USED FOR?
Silica gel is a form of silicon dioxide.
Silica Gel's chemical make-up and high surface area allow it to easily absorb water, making it a useful drying agent (i.e., desiccant).

Silica gel packets are used in pill bottles to decrease moisture, which helps preserve the pills.
Silica Gel is usually available as beads, granules, or crystals in a permeable bag or, less often, in a cylindrical canister.

The beads or granules are clear or white, unless coated with an indicator to tell you whether the silica gel has already absorbed moisture and should be replaced.

Diagnostic test strips, drug test kits, and devices used for inhaling medications may contain silica gel.
The packets of Silica Gel are also found in shoes, clothing, electronic equipment, cameras, pocketbooks, wallets, and other non-medical items.
Food grade silica gel is safe for food storage.

BENEFITS of SILICA GEL:
*Highly effective desiccant: 
Silica Gel adsorbs up to 40% of its weight in water.

*Regenerable: 
Silica Gel can be reused after heating (120–150 °C drives off moisture).

*Chemically inert: 
Silica Gel does not react with most materials, safe for packaging.

*Non-toxic and odorless: 
Silica Gel does not alter the quality of goods it protects.

*Visual indicators: 
Colored silica gels (blue/orange/green) provide clear signals when saturated.

*Versatile: 
Suitable for industrial, commercial, and household applications.

 
CHARACTERISTICS of SILICA GEL:
*Porous structure: 
Silica Gel creates a huge surface area for adsorption.

*Amorphous: 
Non-crystalline silica with irregular shape.

*Non-corrosive: 
Safe for metals, electronics, and sensitive items.

*Reusability: 
Silica Gel can be recycled multiple times without significant loss of capacity.

*Thermal stability: 
Silica Gel works effectively over a wide temperature range (-40 °C to +150 °C).

PROPERTIES of SILICA GEL:
Chemical formula: 
SiO₂

Molecular weight: 
approximately 60.08 g/mol

Appearance: 
Transparent hard beads in dry form; generally translucent or opaque granules

Odor: 
Odorless

Specific surface area of Silica Gel: 
Ranges from ~500 to 950 m²/g (for high-purity forms); typical value is around 600 m²/g

Density: 
Bulk density approximately 0.1 g/cm³ (range: 0.05–0.3 g/cm³) for bead forms; true density ~2.2 g/cm³

Melting/Sublimation point:
Melting point for crystalline silica is >1710 °C; silica gel, being amorphous, has no defined melting point

Solubility: 
Silica Gel is practically insoluble in water and common solvents

Adsorption capacity: 
Silica Gel adsorbs up to ~37% of its weight in moisture; reversible upon heating (regeneration ~120 °C)
Silica gel is usually considered non-toxic.
Accidentally swallowing a silica gel packet should not result in symptoms unless the person chokes on it.

HISTORY of SILICA GEL:
Silica gel was in existence as early as the 1640s as a scientific curiosity.
Silica Gel was used in World War I for the adsorption of vapors and gases in gas mask canisters.
The synthetic route for producing silica gel was patented in 1918 by Walter A. Patrick, a chemistry professor at Johns Hopkins University.

Types
**Type A – clear pellets, approximate pore diameter: 2.5 nm, drying and moistureproof properties, can be used as catalyst carriers, adsorbents, separators and variable-pressure adsorbent.

**Type B – translucent white pellets, pore diameter: 4.5⁠–⁠7.0 nm, liquid adsorbents, drier and perfume carriers, also may be used as catalyst carriers, cat litter.

**Type C – translucent, micro-pored structure, raw material for preparation of silica gel cat litter.
Additionally dried and screened, it forms macro-pored silica gel which is used as drier, adsorbent and catalyst carrier.

Silica alumina gel - light yellow, chemically stable, flame-resistant, insoluble except in alkali or hydrofluoric acid.
Superficial polarity, thermal stability, performance greater than fine-pored silica gel.

Stabilizing silica gel - non-crystalline micro-porous solid powder, nontoxic, flame-resisting, used in brewery of grains for beer to improve taste, clearness, color, and foam and for removal of non-micro-organism impurities.

PROPERTIES of SILICA GEL:
Silica gel's high specific surface area—around 750–800 m2/g (230,000–240,000 sq ft/oz)—allows it to adsorb water readily, making it useful as a desiccant (drying agent).
Silica gel is often described as "absorbing" moisture, which may be appropriate when the gel's microscopic structure is ignored, as in silica gel packs or other products.

However, material silica gel removes moisture by adsorption onto the surface of its numerous pores rather than by absorption into the bulk of the gel.
Silica gel is able to adsorb up to 37% of its own weight in moisture in high-humidity environments.

This moisture can be released upon heating at about 120 °C (248 °F) for 1–2 hours.
This makes Silica Gel reusable multiple times with very little, if any, loss of efficiency.

PREPARATION of SILICA GEL:
An aqueous 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)2[CoCl4] or cobalt(II) chloride CoCl2 is added.

This will cause the gel to be blue when dry and pink when hydrated.
Due to a link between the cobalt chloride and cancer, it has been forbidden in Europe for use in silica gel.
An alternative indicator is methyl violet which is orange when dry and green when hydrated

REGENERATION of SILICA GEL
Once saturated with water, the gel may be regenerated by heating it to about 120 °C (248 °F) for 1–2 hours.
Some types of silica gel will "pop" when exposed to enough water.
This is caused by breakage of the silica spheres when contacting the water.

Regenerating silica gel is important for both economic and environmental reasons.
Silica Gel can be regenerated thermally or chemically.

Chemical methods involve the use of desiccating agents or solvents to desorb water from silica gel, though these are generally less practical for routine regeneration.

Thermal regeneration can be applied also to packed silica gel beds without opening them, and can be done by conventional heating in an oven at a temperature around 120 °C.

Another option for thermal regeneration is by using microwaves to apply heat more evenly and reduce regeneration time compared to conventional ovens, but this process should be tightly controlled to avoid overheating.

Yet another option to apply heat is using a solar heater with a compound parabolic concentrator.
There are also studies on using ultrasonic waves to remove water molecules from silica gel at 45–90 °C which are lower temperatures than that of conventional heating.

WHY DOES SILICA GEL CHANGE COLOR?
Some silica gels are coated with orange/yellow or blue indicators.
These indicator chemicals change color to let you know when silica gel has absorbed moisture and needs to be replaced.

Silica gel coated with indicators is not used to protect medicines or food from moisture.
Rather, Silica Gel is used to keep electronic equipment dry to avoid corrosion.

Orange/yellow silica gel desiccants usually contain methyl violet and turn green when moist.
Blue silica gel desiccants are coated with an indicator called cobalt chloride.

When blue silica gel becomes moist, the cobalt chloride changes color from blue to pink, which indicates that the silica gel should be replaced.
While cobalt chloride is toxic, the concentration is low (i.e., 1% or less) and therefore even cobalt-containing silica gel is usually safe if accidentally ingested.

PHYSICAL and CHEMICAL PROPERTIES of SILICA GEL:
Chemical Formula: SiO2
Molar Mass: 60.08 g/mol
Appearance: Transparent beads
Odor: Odorless
Chemical Formula: SiO₂
Molecular Weight: approximately 60.08 g/mol
Appearance: Transparent hard beads in dry form; generally translucent or opaque granules
Odor: Odorless
Specific Surface Area: Ranges from ~500 to 950 m²/g (for high-purity forms);
typical value is around 600 m²/g

Density: Bulk density approximately 0.1 g/cm³ (range: 0.05–0.3 g/cm³) for bead forms; 
true density ~2.2 g/cm³
Melting/Sublimation Point: Melting point for crystalline silica is >1710 °C; 
silica gel, being amorphous, has no defined melting point
Solubility: Practically insoluble in water and common solvents
Adsorption Capacity: Adsorbs up to ~37% of its weight in moisture; 
reversible upon heating (regeneration ~120 °C)
CAS / EC: 7631-86-9 / 231-545-4 (amorphous); 112926-00-8 (precipitated)
Formula / MW: SiO₂ / ~60.08 g/mol
Appearance: Transparent/opaque beads or gel granules

Surface Area: ~500–950 m²/g
Density: Bulk: ~0.1 g/cm³; true: ~2.2 g/cm³
Adsorption: Up to ~37% water by weight; regenerable via heating
Solubility: Insoluble in water
Uses: Desiccant, indicator, chromatography, food additive, filtration, preservation
Chemical Formula: SiO₂·nH₂O (amorphous hydrated silica)
Molar Mass: Approx. 60.08 g/mol (SiO₂ basis)
Appearance: Granular, hard, translucent to white solid beads 
(sometimes orange, blue, or green when impregnated with indicators)

Odor: Odorless
Density: ~0.7 g/cm³ (bulk), ~2.2 g/cm³ (true density)
Surface Area: 300–1000 m²/g
Porosity: ~0.5–0.6 cm³/g
Melting Point: ~1600 °C (decomposes before melting)
Solubility: Insoluble in water and organic solvents, soluble in hydrofluoric acid
pH (suspension in water): ~4–7
Vapor Pressure: Negligible
Stability: Stable, non-combustible

FIRST AID MEASURES of SILICA GEL:
-Description of first-aid measures
*General advice:
Show this material safety data sheet to the doctor in attendance.
*If inhaled:
After inhalation: 
Fresh air.
*In case of skin contact: 
Take off immediately all contaminated clothing. 
Rinse skin with
water/ shower.
*In case of eye contact:
After eye contact: 
Rinse out with plenty of water. 
Call in ophthalmologist. 
Remove contact lenses.
*If swallowed:
After swallowing: 
Immediately make victim drink water (two glasses at most). 
Consult a physician.
-Indication of any immediate medical attention and special treatment needed.
No data available

ACCIDENTAL RELEASE MEASURES of SILICA GEL:
-Environmental precautions:
Do not let product enter drains.
-Methods and materials for containment and cleaning up:
Cover drains. 
Collect, bind, and pump off spills. 
Observe possible material restrictions. 
Take up dry. 
Dispose of properly. 
Clean up affected area.

FIRE FIGHTING MEASURES of SILICA GEL:
-Extinguishing media:
*Suitable extinguishing media:
Carbon dioxide (CO2) 
Foam 
Dry powder
*Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.
-Further information:
Prevent fire extinguishing water from contaminating surface water or the ground water system.

EXPOSURE CONTROLS/PERSONAL PROTECTION of SILICA GEL:
-Control parameters:
--Ingredients with workplace control parameters:
-Exposure controls:
--Personal protective equipment:
*Eye/face protection:
Use equipment for eye protection. 
Safety glasses
*Body Protection:
protective clothing
*Respiratory protection:
Recommended Filter type: Filter A 
-Control of environmental exposure:
Do not let product enter drains.

HANDLING and STORAGE of SILICA GEL:
-Conditions for safe storage, including any incompatibilities:
*Storage conditions:
Tightly closed. 
Dry.

STABILITY and REACTIVITY of SILICA GEL:
-Chemical stability:
The product is chemically stable under standard ambient conditions (room temperature).
-Possibility of hazardous reactions:
No data available