Silica gel, << SIHL uh kuh jehl, >> is a nontoxic, glassy solid commonly used as a desiccant, a substance that removes moisture. Silica gel is made of silicon dioxide (SiO2) with water bound to it. Many water molecules can attach to each SiO2 molecule. Also, silica gel particles have many pores. Thus, they can adsorb (bind) large amounts of water and certain other chemicals. Packets of silica gel are packaged with certain foods, medicines, leather goods, precision instruments, and electronic devices to collect water vapor that might otherwise damage the contents.
Drug manufacturers, petroleum refiners, and other processors separate or purify chemical substances by passing them through a column of silica gel. Although silica gel binds certain molecules, it does not react with them. The molecules can thus be released and collected, and the silica gel can be reused.
