What are non-hygroscopic substances

Hygroscopy (v. Greek hygrós "Damp, wet" + skopein In chemistry and physics, “look at” refers to the ability to bind moisture from the environment (usually in the form of water vapor from the air humidity). The absorbing substances - insofar as they are solid substances - usually dissolve or clump together through the absorption of water. This does not apply to porous materials, which bind the water in their cavities.

Hygroscopy is often mistakenly called hydroscopy (due to the ancient Greek word το ύδορ “The water” - pronounced “to hydor”). The German "hydros" comes from the genitive, which is then written in Greek ύδρος.

Undesirable effects

This property is often undesirable in practice, for example when table salt clumps together as a result of the moisture in the air. However, table salt is not itself hygroscopic; the absorption of moisture results from traces of magnesium chloride in the table salt. This effect is also important in other areas. Vehicle brake fluid also tends to bind water. The brake fluid heats up when braking. This leads to the formation of water vapor in the brake system, which leads to a drop in brake pressure. For this reason, it is recommended that the brake fluid be changed every two years. The hygroscopic effect is also undesirable in model making, since the fuel used for glow igniter engines contains nitromethane, which is hygroscopic and is so often spoiled by improper storage. In construction, hygroscopic material is a disadvantage, as the water particles in the building material are converted into ice crystals in the event of sudden frost. These crystals have a larger volume than the water particles and thus cause the material to flake off. For this reason, frost-resistant materials are required for sensitive components. H. these materials must not be hygroscopic.

Hygroscopy in building materials

The hygroscopicity of building materials, especially that of interior construction (such as plaster, floor coverings and wood), can have a decisive influence on the humidity of a room and thus on the room climate as a whole. The building materials, which absorb a lot of moisture from the air and can release it again very quickly if necessary (hygroscopic building materials: largely all plant and animal building materials such as wood or sheep's wool) are in favor of other building materials (e.g. plastics, metals, concrete) pleasant room climate particularly recommended.

Category: substance property