Silica-gel is an absorbent made by solidifying the colloidal solution of silicic acid.
It's also called anti humidity agent or humidity absorbing agent.
During World War I, Dr. Walten A. Patrick from John Hopkins University invented it as an absorbent for GAS MASK container.

Gel means the state of manufactured property.
Hard glass type material is usually used and its appearance is like transparent crystal and it's composed of Sio.
According to Mohs hardness table, Silicagel is No.5 and this means it's softer than usual glass.
It has highly porous structure and pores are very uniform in size and distribution.

The surface area of fine pores of Silica-gel depends on manufacturing method but the surface area of internal pores of diameter 1/16 inch is 250,000 times of the external surface area.
Silica-gel is a group of granular amorphous particles where fine holes are connected to each other in an extensive mesh and its huge surface area (1g 300~400) promotes natural absorbing and condensation phenomena which lead to excellent absorbing capability for water, alcohol, and other compounds. It's no color and no smell and it's a dehumidifying agent not harmful to human body.

 < Graph1> Moisture absorption rate per silica-gel type
 < Graph2 > Moisture absorption rate per silica-gel B type
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