What is silica gel?

Silica gel is a kind of granular porous silica hydrate, which is made by adding acid to sodium silicate, washing and drying. Mainly used as desiccant and adsorbent for column chromatography and thin layer chromatography. Although it is called "glue", it is actually a transparent or milky solid. Silicone is sometimes called silica gel, but it is actually a silicon-containing compound with completely different properties and uses.

Silica gel was discovered by scientists as early as 1640. 19 19, Walter a Patrick, a professor of chemistry at Johns Hopkins university, applied for a production patent. During World War I, it was used as an absorbent for gas masks. ..

Extended data

nature

Absorbent silica gel can be regenerated by heating at120 C for two hours.

Soak silicic acid gel in cobalt chloride or ammonium cobaltate ((NH? )? CoCl？ ) solution, and then dried and activated to obtain color-changing silica gel, which can be used to indicate the water absorption degree of silica gel. This is because anhydrous cobalt chloride (CoCl? ) is blue, while cobalt chloride hexahydrate (CoCl? 6H？ O) It's red.

In daily life, silica gel is often packed in some paper bags or bags made of semi-permeable membrane resin to absorb water, control humidity and prevent some items from deteriorating. Silicone bags are generally marked with the words "Do not eat". It will cause irritation to respiratory system, digestive system, skin and eyes. Some discolored silica gels also contain humidity indicators such as cobalt chloride. Cobalt chloride is a toxic substance, which belongs to IARC Class II carcinogen and may cause cancer.

Baidu encyclopedia-silica gel