desiccant

A substance that removes part of the moisture from a moist substance. For example, calcium sulfate and calcium chloride are dried by combining with water to form hydrate; Physical desiccants, such as silica gel and activated alumina, are dried by physically adsorbed water. The control of moisture is closely related to the yield of products. As for food, under proper temperature and humidity, bacteria and molds in food will multiply at an amazing rate, causing food deterioration, moisture and discoloration. Electronic products will also cause metal oxidation due to high humidity, resulting in poor performance. The use of desiccant is to avoid the occurrence of defective products caused by excess water.

Concentrated H2SO4: often used as a desiccant for H2, O2, CO, SO2, N2, HCl, CH4, CO2, Cl2 and other gases.

Anhydrous calcium chloride CaCl2 (fused): it cannot be used to dry ammonia, alcohol, amine, acyl, ketone, aldehyde, ester, etc.

Anhydrous magnesium sulfate: commonly used to dry organic reagents.

Solid sodium hydroxide and alkali lime: commonly used to dry hydrogen, oxygen, ammonia, methane and other gases.

Discolored silica gel: driable amine, NH3, O2, N2, etc.

Activated alumina (Al2O3): large water absorption, fast drying speed, regeneration (400-500K baking).

Anhydrous sodium sulfate: the drying temperature must be controlled within 30 ℃, and the dryness is worse than that of anhydrous magnesium sulfate.

Calcium sulfate: it can dry H2, O2, CO2, CO, N2, Cl2, HCl, H2S, NH3, CH4, etc.