Desiccation

From Encyclopedia Jr, free information reference for Kids

Desiccation refers to the state of extreme dryness, or the process of extreme drying. A desiccant is a substance that absorbs or adsorbs water. It is most commonly used to remove humidity that would normally degrade or even destroy products sensitive to moisture. Silica gel, calcium sulfate, montmorillonite clay, and molecular sieves are commonly used as desiccants.

[edit] Science

A vacuum desiccator (left) and desiccator (right). Silica gel with cobalt chloride indicator placed in the lower shelf is used as the desiccant.

Toluene is refluxed with sodium and benzophenone to produce dry, oxygen-free toluene. The toluene is dry and oxygen free when the intense blue coloration from the benzophenone ketyl radical is observed.

[edit] Desiccator

In science, a desiccator is a heavy glass container used in practical chemistry for making or keeping small amounts of material very dry. The material is placed on a shelf, and a drying agent or desiccant, such as dry silica gel or anhydrous caustic soda, is placed below the shelf.

Often some sort of humidity indicator is included in the desiccator to show, by color changes, the level of humidity. These indicators are in the form of indicator plugs or indicator cards. The active chemical is cobalt chloride (CoCl₂). Anhydrous cobalt chloride is blue. When it bonds with two water molecules, (CoCl₂•2H₂O), it turns purple, and its hexahydrate form (CoCl₂•6H₂O) is pink.

[edit] Drying solvents

Desiccants are also used to dry solvents, typically used for moisture free reactions. While different desiccants are used differently, the general method involves stirring the solvent to be dried with the drying agent.

Usually, the drying agent will react with moisture to form a solid insoluble in the solvent being purified. It can be removed simply by filtering. For more demanding applications, requiring very pure, air-free and/or moisture free solvents, a distillation still used with a desiccant able to remove air, moisture, and other impurities all at once.

[edit] Biology/Ecology

In Biology & Ecology, desiccation refers to the drying out of a living organism, such as when aquatic animals are taken out of water, or when plants are exposed to sunlight or drought. Ecologists frequently study and assess various organisms' susceptibility to desiccation. Since all life is water-based, desiccation of any organism will ultimately result in death.

[edit] Broadcasting

In broadcast engineering, a desiccator may be used to pressurize the feedline of a high-power broadcast station. Because it carries very high electrical power levels from the transmitter to the antenna, the feedline must have a good dielectric. Because it must also be lightweight so as not to overload the radio tower, air is often used as the dielectric. Since moisture can condense in these lines, desiccated air or nitrogen gas is pumped in. This pressure also keeps water or other dampness from coming in the line at any point along its length.

[edit] Other uses

Desiccated coconut is the dried, finely shredded flesh of the coconut, much used in cooking desserts. It is also used in other types of food preservation.

In Industry, Desicant Air Filters are critical when managing hydrocarbons for filtering the air on bulk storage facilities.

Mild desiccation of the air can be accomplished with a dehumidifier.

Uncooked rice is an effective household desiccant.

Desiccants can also be used in environmentally friendly air conditioning systems.

A small package of desiccant is commonly included in shoe boxes.

[edit] See also

List of desiccants

[edit] External links

• Desiccant info
• Latest US desiccants patents information.
• A Desiccant Requirements Calculator