Silica gel
Silica gel is a hard, granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate.
Contents
Properties
Physical
Silica gel are a type of hard, spherical beads, of various sizes, either colorless or having moisture sensitive dye. Silica gel's high specific surface area (around 800 m2/g) allows it to adsorb water readily, making it useful as a desiccant (drying agent). Once saturated with water, the gel can be regenerated by heating it to 120 °C for 1–2 hours. Just like in the case of molecular sieves, heating the beads too hard may crack them. Certain types of silica gel will "pop" when exposed to enough water, causing them the spheres to break down.
Chemical
As they're made of silicon dioxide, silica gel beads will only react with alkali, hydrofluoric acid and various fluorine compounds.
Availability
Silica gel can be found in many products, ranging from clothes, shoes, all packaging, furniture, electronic and mechanical devices, inside small labeled bags.
While most caps of certain medical drug tubes contain silica gel, some also contain other drying agents that fizz on contact with water.
Silica gel litter used for adsorbing cat urine and other fluids can be cheaply purchased from various vet shops. Some may contain perfume, while most tend to have a few colored flakes (generally blue) mixed with the colorless ones, which, due to their large size can be easily removed by hand.
Lastly, silica gel beads can be bought in bulk from various suppliers.
Crystalline silica gel can be purchased from chemical suppliers or online.
Projects
- Dry solvents
- Purify gas streams
- Reactor catalyst
- Column chromatography
- Filtering extremely fine suspensions
Handling
Safety
Silica gel may irritate the skin when anhydrous. Crystalline silica dust can cause silicosis, but synthetic amorphous silica gel does not, as it is indurated.
Storage
In sealed bottles, just like any desiccant: away from any moisture or volatile compounds. Crystalline silica gel should also be kept in sealed bags, inside closed containers.
Disposal
Silica gel can be dumped in trash or mixed with cement.
