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1. What are the common desiccants for high school chemistry:
Concentrated sulfuric acid, phosphorus pentoxide solid caustic soda, lime and soda lime (mixture of sodium hydroxide and calcium oxide) anhydrous calcium chloride, anhydrous magnesium sulfate anhydrous copper sulfate, calcium chloride, food grade calcium chloride, magnesium chloride , ammonium chloride, food grade magnesium chloride, food grade ammonium chloride.
Second, the classification of commonly used desiccants:
The first type is an acidic desiccant. There are concentrated sulfuric acid, phosphorus pentoxide, silica gel, etc.;
The second type is an alkaline desiccant, which has solid caustic soda, lime and soda lime (a mixture of sodium hydroxide and calcium oxide);
The third type is a neutral desiccant such as anhydrous calcium chloride, anhydrous magnesium sulfate and the like.
Third, the performance and use of common calcium chloride desiccant are as follows:
1. Concentrated H2SO4: has a strong water absorption and is commonly used to remove moisture from gases that do not react with H2SO4. For example, it is often used as a desiccant for gases such as H2, O2, CO, SO2, N2, HCl, CH4, CO2, and Cl2.
2. Anhydrous calcium chloride: It is widely used because of its low cost and strong drying ability. It has a fast drying speed and can be regenerated with a dehydration temperature of 473K. It is generally used to fill dryers and drying towers, dry medicines and various gases. Can not be used to dry ammonia, alcohol, amines, acyl, ketones, aldehydes, esters, etc.
3. Anhydrous magnesium sulfate: It has a strong drying ability and generates MgSO4·7H2O after water absorption. It has a fast water absorption effect, high efficiency and low cost, and is a good desiccant. Often used to dry organic reagents.
4. Solid sodium hydroxide and soda lime: fast water absorption, high efficiency and low price. It is an excellent desiccant, but it can not be used to dry acidic substances. It is often used to dry gases such as hydrogen, oxygen and methane.
5. Color-changing silica gel: commonly used to keep the instrument and balance dry. It turns red after water absorption. The failed silica gel can be used after drying and regeneration. The amine, NH3, O2, N2, etc. can be dried.
6. Activated Alumina (Al2O3): It has a large water absorption, fast drying speed and can be regenerated (400-500K baking).
7. Anhydrous sodium sulfate: The drying temperature must be controlled within 30 ° C, and the drying property is inferior to that of anhydrous magnesium sulfate.
8. Calcium sulfate: It can dry H2, O2, CO2, CO, N2, Cl2, HCl, H2S, NH3, CH4, etc.
Note: Anhydrous copper sulfate (CuSO4) (anhydrous copper sulfate to white) also has a certain degree of dryness, and after water absorption, it turns into blue copper sulfate pentahydrate (CuSO4·5H2O), but it is generally not used as a desiccant.