Hygroskopie

Hygroskopie (v. griech.: hygrós = damp, wet + skopein = look at) designation in chemistry and physics the characteristic to bind humidity from the environment (usually in the form of water vapour from the air humidity). The taking up materials - so far it around firm of materials acts - dissolve or mostly clump by the water absorption. From it porous materials , which bind the water in their cavities, are excluded.

Hygroskopie is often falsely called hydraulic copy (due to the Greek word hydrós = water).

applications

strong hygroscopic materials like for example calcium chloride, magnesium chloride or Silicagel are used as desiccators. The latters remain being appropriate also in the satisfied condition rieselfähig and form-stably and often for articles, which are to be protected against humidity (electronic or optical devices), in a bag. Another application is the connection of water in refridgerators (e.g. Absorption refrigerator). The steam pressure of the water in the above atmosphere can be reduced by hygroscopic materials, if the area is close. As basis for the fact it is to be regarded that the hygroscopic thus water-attractive material possesses a smaller steam pressure than the steam pressure of the surrounding area.

unwanted effects

the characteristic is in practice often unwanted, for example, if common salt clumps due to taken up air humidity. Common salt is not however even hygroscopically, the moisture absorption resulted from traces of magnesium chloride in the common salt. Also within other ranges is this effect of importance. The brake fluid of vehicles is inclined likewise to bind water. With braking if the water is then heated up, it comes to the water vapour formation in the brake system, whereby the brake performance drops rapidly. Therefore a two-year change of the brake fluid is prescribed. Also in the model construction the hygroscopic effect is unwanted, since the Sprit used for electric primer engines contains Nitromethan, which is hygroscopic, and so often by inappropriate storage one spoils.

Wiktionary: Hygroskopie - word origin, synonyms and translations
 

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