Dessicants

Dessicants are substances that absorb or adsorb moisture from the air, thus keeping an environment dry. They are commonly used to prevent spoilage, corrosion, and mold growth in various products and enclosed spaces. The process by which they remove moisture is known as dessication.

There are two main types of dessicants: those that absorb moisture and those that adsorb it. Absorbing dessicants, like calcium chloride, actually draw water molecules into their chemical structure, often forming a hydrated salt. Adsorbing dessicants, such as silica gel and activated alumina, have a porous surface with a large surface area that traps water molecules physically onto their surface.

Common examples of dessicants include silica gel, which is often found in small packets in shoe boxes or electronics packaging, and calcium chloride, used in larger quantities for industrial drying or as a de-icing agent. Activated charcoal and molecular sieves are other types of dessicants used in specialized applications.

The effectiveness of a dessicant depends on its capacity to hold water and its equilibrium relative humidity. Some dessicants can be regenerated by heating them to drive off the absorbed or adsorbed moisture, allowing for reuse. Dessicants play a crucial role in preserving the quality and extending the shelf life of many consumer goods and industrial materials.