silicone rubber can be used as a desiccant, and can be reused. Silica gel is a porous material of different particle size formed by dehydration of silicic acid gel mSiO2 / nH2O. With open porous structure, specific surface (unit mass surface area) is very large, can adsorb many substances, is a good desiccant, adsorbent and catalyst carrier. Adsorption of silica gel is mainly physical adsorption, renewable and repeated use. In the alkali metal silicate (such as sodium silicate) solution with acid, the acid electrolyte, then adding a certain amount of mixing, which generates silicate gel; or in sodium silicate solution is strong in acid or ammonium salt can also generate silicate gel. The silicic acid gel is fixed for a few hours to be aged, and then the soluble salt is washed out with hot water, and is dried at 60 to 70 DEG C and activated at about 300 DEG C to obtain silica gel. The silicic acid gel is soaked with cobalt chloride solution and then dried and activated. When used as a desiccant, before the water is blue, red after water absorption, color change can be seen from the degree of water absorption, as well as the need for renewable treatment. Silica gel is also widely used in vapor recovery, oil refining and catalyst preparation.