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|Section2= }} 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 paper packet. In this form, it is used as a desiccant to control local humidity to avoid spoilage or degradation of some goods. Because silica gel can have added chemical indicators (see below) and adsorbs moisture very well, silica gel packets usually bear warnings for the user not to eat the contents. == History == Silica gel was in existence as early as the 1640s as a scientific curiosity. It 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 by chemistry professor Walter A. Patrick at Johns Hopkins University in 1918. In World War II, silica gel was indispensable in the war effort for keeping penicillin dry, protecting military equipment from moisture damage, as a fluid cracking catalyst for the production of high octane gasoline, and as a catalyst support for the manufacture of butadiene from ethanol, feedstock for the synthetic rubber program. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Silica gel」の詳細全文を読む スポンサード リンク
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