Desiccation is the state of extreme dryness, or the process of extremedrying. Adesiccant is ahygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The word desiccation comes from Latin de- 'thoroughly' and siccare 'to dry'.
Desiccation is widely employed in the oil and gas industry. These materials are obtained in a hydrated state, but the water content leads to corrosion or is incompatible with downstream processing. Removal of water is achieved bycryogenic condensation, absorption into glycols, and absorption onto desiccants such assilica gel.[1]
Adesiccator is a heavyglass orplastic container, now somewhat antiquated, used in practicalchemistry for drying or keeping small amounts of materials very dry. The material is placed on a shelf, and a drying agent ordesiccant, such as drysilica gel or anhydroussodium hydroxide, is placed below the shelf.
Often some sort ofhumidity 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 iscobalt chloride (CoCl2).Anhydrous cobalt chloride is blue. When it bonds with two water molecules, (CoCl2•2H2O), it turns purple. Further hydration results in the pink hexaaquacobalt(II) chloride complex [Co(H2O)6]2+.
Inbiology andecology, desiccation refers to the drying out of a living organism, such as when aquatic animals are taken out of water,slugs are exposed to salt, or when plants are exposed to sunlight or drought. Ecologists frequently study and assess various organisms' susceptibility to desiccation. For example, in one study the investigators found thatCaenorhabditis elegansdauer is a true anhydrobiote that can withstand extreme desiccation and that the basis of this ability is founded in the metabolism oftrehalose.[2]
Several bacterial species have been shown to accumulateDNA damage upon desiccation.Deinococcus radiodurans is extremely resistant toionizing radiation. The functions necessary to survive ionizing radiation are also necessary to survive prolonged desiccation.[3] Radiation resistance is considered to be an incidental consequence of the organism's evolutionary adaptation to dehydration, a common physiological stress in nature.[3] The chromosomal DNA from desiccatedD. radiodurans revealed increased DNA double-strand breaks.[4] DNA double-strand breaks are repaired principally by a RecA-dependent recombination process that requires the presence of two genome copies.[4] By this processD. radiodurans can survive thousands of double-strand breaks per cell.[4]
Mycobacterium smegmatismutant strains that are deficient in the ability to repair double-strand breaks by thenon-homologous end joining (NHEJ) pathway are more sensitive to prolonged desiccation during stationary phase thanwild-type strains.[5] NHEJ appears to be the preferred pathway for repairing double-strand breaks caused by desiccation during the stationary phase. NHEJ can repair double-strand breaks even when only one chromosome is present in a cell.
Upon exposure to extreme dryness,Bacillus subtilisendospores acquire DNA-double strand breaks and DNA-protein crosslinks.[6]
Inbroadcast engineering, a desiccator may be used topressurize thefeedline of a high-power transmitter. Because it carries a large amount of energy from thetransmitter to theantenna, the feedline must have lowdielectric losses. Because it must also be lightweight so as not to overload theradio tower, air is often used as the dielectric. Sincemoisture cancondense in these lines, desiccated air ornitrogengas is pumped in. Thispressure also keepswater or otherdampness from coming into the line at any point along its length.
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