Hygroscopicity

Hygroscopicity, the ability of bodies to attract moisture, where part of this moisture can be physically bound as observed in certain hygroscopic substances that eagerly absorb water (such as phosphorus anhydride, calcined copper sulfate, etc.). Hygroscopicity presupposes the presence of molecular and capillary forces between these two bodies. Therefore, if the surface of a body is covered with a substance that does not attract water, then hygroscopicity disappears. As an example of such a change, one can point to the hygroscopicity of cotton wool, which, in its normal state and containing fat on its fibers, is not hygroscopic. When treated with substances that remove fat, cotton wool becomes hygroscopic and easily absorbs water, which is used for surgical purposes.