Silica Gel

Silica gel is a granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate. Silica gel is tough and hard; it is more solid than common household gels like gelatin or agar. 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.

Silica gel is most commonly encountered in everyday life as beads in a small (typically 2 by 3 centimetres (0.79 in × 1.2 in)) paper packet. In this form, it is used as a desiccant to control local humidity to avoid spoilage or degradation of some goods. Because of poisonous dopants (see below) and their very high absorption of moisture, silica gel packets usually bear warnings for the user not to eat the contents.