deliquescing

Deliquescing is a physical process observed in certain chemical compounds, primarily salts. It refers to the ability of a substance to absorb moisture from the atmosphere until it dissolves in the absorbed water, forming a solution. This phenomenon occurs when the vapor pressure of the saturated solution of the compound is lower than the partial pressure of water vapor in the surrounding air. Essentially, the compound is so hygroscopic that it actively draws water from the air and dissolves in it.

Common examples of deliquescing substances include calcium chloride, magnesium chloride, and zinc chloride. These compounds are often used as drying agents or in applications where controlling humidity is important, such as de-icing roads. The rate at which deliquescence occurs depends on factors like the specific compound, its surface area, temperature, and the ambient humidity. If a deliquescing substance is exposed to sufficiently dry air, it will not deliquesce and may even re-crystallize if it was previously in solution. The process is reversible under certain conditions.