The main ingredient of  silica gel is SiO 2 · nH2O, is a well-developed pore structure of porous material. 

Mainly used as sorbent, desiccant and catalyst carrier. According to their 

Pore ​​size distribution can be divided into coarse, pore, pore surface area than the coarse 

Large. The adsorption of water vapor selective at low humidity, 

Large pore gel adsorption, at high humidity, the coarse gel adsorption 

Larger, high-quality silica gel apparent smooth, glistening. From 

Coarse to the pore, milky white, translucent, transparent spherical particles. 

Poor quality of the silica gel, developed pore structure, adsorption is low, there is apparent 

Crack, intensity difference, hair, dirt and not translucent. Analysis of the main reasons the original 

Materials, process indicators, the level of equipment and operating techniques. 

2 main reasons - raw materials 

Sodium 211 

21,111 high iron content, will cause yellow silicone. GBö4209- 

96 in the liquid sodium silicate iron content 0.02%, with this raw material production 

Content of silica Fe2O 3 200 ~ 300ppm. Just the production of silicon 

Plastic appearance can, place a long time, Fe2 + oxidation of all 

Fe3 +, silica gel into a deep yellow. 

21112 A l2O 3, T iO 2, CaO, M gO high of silica gel 

Transparency and strength, the metal oxide content is too high, not only sodium 

Difficult to dissolve, but also filtering is unclear, and even lead to the production of silicone 

No gelation. 

21113 Water insoluble high, affecting the transparency of silica gel, hair, dirt and will 

Silica caused more cracks, more than the production of silicone rubber flap. 

212 sulfuric acid 

21211 sulfuric acid color must be clear and transparent, to the small settlement of 48 

Time before use, otherwise, the apparent impact of silica gel. 

21212 heavy metal content, will affect the gel strength. 

In short, the production of raw materials, silica gel was very strict, to control 

A l2O 3, Fe2O 3, T iO 2, CaO, M gO and other impurities, with this 

Kinds of raw materials to produce the appearance of fine silica gel, place a long time is not yellow.