Dehumidifier: Salt has a hygroscopic effect
Dehumidifiers work by using hygroscopic salts. Here is an explanation of the chemical concept behind it.
Salts in dehumidifiers
- First of all, you should know that a hygroscopic salt is a salt that is able to draw moisture from the environment. This is mostly water from humidity.
- Hygroscopic salts are contained in dehumidifiers that can fulfill their function in this way. Such salts are also called drying agents.
- Hygroscopic salts can incorporate water into their crystal structure and thus bind it.
- A dehydrating salt known to you from everyday life is NaCl - common table salt. If it is stored in the open, it quickly clumps together. This is also the main reason why you should store your household salt in sealed cans. In the salt shaker, for example, a few grains of rice can help, as they absorb the water even faster.
- Calcium chloride is often used in dehumidifiers.
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Examples of hygroscopic salts
- Two of the most commonly used desiccants in the laboratory are calcium chloride and phosphorus pentoxide. Which one you use is usually a matter of taste.
- A certain amount of CaCl2 can bind six times as much water molecules. This happens according to the chemical formula CaCl2 + 6 H.2O -> CaCl2* 6H2O. This process generates heat.
- A very effective desiccant is P4O10. The reaction with the water from the humidity takes place in three stages. 1. P.4O10 + 2 H.2O -> H4P.4O12, 2. H4P.4O12 + 2 H.2O -> 2 H4P.2O7, 3. H4P.2O7 + H2O -> 2 H3PO4.
- Another drying agent that is dangerous to use is Mg (ClO4)2. The reaction equation for this is Mg (ClO4)2 + 2 H.2O -> Mg (ClO4)2* 2H2O.
- In their crystal structure, zeolites have pores and / or channels into which they can take up water molecules.
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