Silica gel

Silica gel is a granular, porous form of silica made synthetically from sodium silicate. Despite the name, silical gel is a solid. It is usually distributed in the form of beads, which are packaged in a semi-permiable packet. It was created at Johns Hopkins University, Baltimore, Maryland in the 1920s. Its high porosity, around 800 m²/g, allows it to adsorb water readily, making it useful as a desiccant (drying agent). It can reduce the relative humidity in a closed space to around 40%. Once saturated with water, the gel can be regenerated (dried) by heating it to 150°C (300°F) for 1.5 hours per liter (about 1 dry quart measure or about 30oz weight) in a thick-walled Pyrex dish. The gel is non-toxic, non-flammable and chemically unreactive. Some of the beads may be doped with a moisture indicator, such as cobalt (II) chloride, a chemical that changes color when moist.

External link

\n*Silica gel: do not eat! site describing silica gel in great detail.\n*Silica Gel with Moisture indicator: Instructions for use detailed use and regeneration (re-drying) info