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Removal of water from any substance.
(organic chemistry)
An elimination reaction in which a molecule loses both a hydroxyl group (OH) and a hydrogen atom (H) that was bonded to an adjacent carbon.



splitting off of water from organic or inorganic compounds. Dehydration can be achieved thermally (mostly in the presence of catalysts) or chemically by the action of dehydrating agents (water-binding substances). The formation of ethylene from ethyl alcohol is an example of dehydration performed by passing ethyl alcohol through a tube containing aluminum oxide (catalyst) at 300°–400°C or by heating it with concentrated sulfuric acid (dehydrating agent) to 170°C:

CH3 —CH2OH → CH2 ═CH2 + H2O

The formation of ethylene is an example of intramolecular dehydration. However, heating the excess of ethyl alcohol with sulfuric acid to 140°C leads mainly to intermolecular dehydration with the resulting formation of diethyl ether:

CH3CH2 —O—H + H—O—CH2CH3 → CH3CH2 —O—CH2CH3 + H2O

Intramolecular dehydration of acetic acid CH3COOH yields ketene CH2=C=O, whereas the intermolecular dehydration of acetic acid yields acetic anhydride (CH3CO)2O. Dehydration of the amides CH3CONH2 yields nitriles CH3C≡N. Formation of nitrogen pentoxide from nitric acid in the presence of phosphorus pentoxide is an example of the dehydration of an inorganic substance:

Dehydration also includes the processes leading to the removal of water of crystallization from crystal hydrates and the removal of water bound by adsorption forces. Dehydration is the opposite of hydration.




loss of water by an organism to a point below the physiological norm. Animals die when they lose 20–25 percent of their body water, and disorders arise when the water loss reaches 10 percent. Dehydration may develop as a result of excessive water loss (repeated vomiting, diarrhea, excessive perspiration, extensive burns) or restriction of water intake.

Excessive water loss leads to hypo-osmolar dehydration, a condition in which the body loses a significant quantity of electrolytes along with the excreted fluids, the osmotic pressure in the cells is higher than in the interstices of tissues, and fluid enters the cells. When the water intake is restricted, the loss of fluid substantially exceeds the loss of electrolytes. This leads to hyperosmolar dehydration, a condition in which the osmotic pressure in the interstices of tissues increases and water passes from the cells to the extracellular space, as a result of which the cells become dehydrated and die.

Dehydration is accompanied by agonizing thirst, which is more difficult to endure than the hunger caused by deprivation of food. The secretion of all digestive glands is reduced, the blood thickens, and the blood viscosity increases. The changes in the blood lead to serious disorders of blood circulation and to disruption of renal function. Acute dehydration may lead to mental disorders, collapse, and sometimes death. Dehydration develops considerably more rapidly in children than in adults, since in children, especially infants, the amount of water excreted through the kidneys, skin, and lungs per unit of body surface is far greater than in adults. In pathological conditions causing hypo-osmolar dehydration, thirst should be quenched by drinking salted water to compensate not only for the water loss but the loss of electrolytes as well. Treatment consists in removing the primary cause of dehydration.



The removal of water vapor from air by the use of absorbing or adsorbing materials.
References in periodicals archive ?
Retrospective Analysis of 104 Chronic Wounds Healed with Dehydrated Human Amnion/Chorion Membrane Allografts in the VA Setting Over a 2 Year Period" authored by Joseph Terebessy, DPM.
Agricultural authorities initiated the practice in south Xinjiang last year by building 1,500 drying rooms which dehydrated over 20,000 tonnes of apricots in 13 counties.
Mona Bahouth, MD, a stroke researcher at Johns Hopkins Hospital in Baltimore, Maryland, notes that "Previous studies suggest that about 60% of people are dehydrated at the time of stroke.
And in nearly every single instance, when a dehydrated dog is offered water after exercise, it doesn't consume enough.
Pedialyte, a liquid meant for dehydrated infants suffering from vomiting and diarrhea, also works wonders after a long night of partying, the New York Daily News reported.
SOS: The combination of planes, pina coladas and sun-baking can lead to a seriously dehydrated complexion.
While suffering from a stomach virus, Secretary Clinton became dehydrated and fainted, sustaining a concussion.
I am pleased to announce that Alejandro Ballesteros has been promoted to President, Sensient Dehydrated Flavors.
You must learn what can happen to your body when it becomes dehydrated.
For the dehydrated olives: Place olives in dehydrator set at 110
AA great way to tell if you're dehydrated or hydrated is by using the colour of your urine as an indicator.
This removes water from the system too and the pup can become more Q dehydrated, not less.