Selecting a Desiccant on Amazon.com
A desiccant is a solid substance that retains moisture and helps to reduce humidity. Typically available in granular or beaded form, some desiccants include silica, alumina, Montmorillonite clay, activated charcoal, calcium sulfate, calcium chloride, and molecular sieves. Some desiccants work by absorption, while others adsorb moisture, a process in which water adheres to the surface of the sorbent particle. They are used in storage, scientific, pharmaceutical, industrial, manufacturing, and food processing applications to dry, or desiccate, another substance, environment, or container.
In food processing, a desiccant may be added to a food product to help maintain crispness or reduce moisture. Some desiccants protect sensitive electronic equipment from humidity that might cause corrosion, a short circuit, or malfunction. Others are used in shipping containers or storage applications to maintain dryness and reduce the potential for corrosion, mold, and mildew growth. One type of desiccant, silica gel, is commonly used in chromatography (a process in analytical chemistry for separating mixtures) as the stationary phase that adsorbs part of the compound in a chemical separation. In industrial settings, desiccants can be used to control the water level in a gas stream.
Considerations when choosing a desiccant include the application requiring desiccation, the size and temperature of the space to be dried, the level of moisture present in the space, and the packaging required. Some desiccants have greater adsorption ability than others due to the size of their pores and surface area, and they may work better in environments with higher relative humidity. Changes in temperature can affect the level of humidity in the vicinity of the desiccant, which can affect its drying capability. Desiccants are commonly packaged in bulk containers or in small packets, such as silica gel packets found in food or retail products to prohibit an accumulation of moisture. Sometimes, a desiccant has an added humidity indicator that causes it to change color when saturated with water. Drierite is made from calcium sulfate and manufactured by the W.A. Hammond Drierite Company.