Hydrate



Hydrate is a term used in organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood.

In organic chemistry, a hydrate is a compound formed by the addition of water or its elements to a host molecule. For example, chloral hydrate, CCl3—CH(OH)2, which can be formed by reaction of water with chloral, CCl3—CH=O.

Other molecules have been labeled as hydrates for historical reasons. methanol is often sold as “methyl hydrate”, implying an incorrect formula CH3OH2, although the correct formula is CH3—OH.

In inorganic chemistry, hydrates contain water molecules that are either bound to a metal center or crystallized with the metal complex. Such hydrates are also said to contain "deuterium, then the term deuterate may be used in place of hydrate.

    A colorful example is cobalt(II) chloride, which turns from blue to magenta (red) upon hydration, and can therefore be used as a water indicator.

The notation of hydrous compound · nmethane hydrate.

A substance which has lost water is referred to as an anhydrous.

Construction

The presence of hydrates is quite purposeful in the three fields of endeavour. Generally, in construction and refractories, inorganic binders are often deprived of water during manufacture. For instance, both in exothermic chemical reaction with water.

Generally, the longer one can keep cementitious products wet immediately after placement, the better. The wetter cementitious products are kept, the more water will be converted into hydrates, instead of evaporating off due to the heat of hydration and other environmental influences. Premature drying is a cause for severe concrete problems, such as cracking and shrinking.

Passive fire protection

Avoiding premature drying is important to all other cementitious building products, such as spray fireproofing and firestop mortars in particular, where the slightest cracking can lead to rejections. The chemically bound water, is the source for concrete or plaster.

Space physics

Fire-resistance duration is important to many high-tech PFP products such as intumescent and endothermic paints, wraps and tiles, such as those used in space physics, for re-entry vehicles.

See also

  • Passive fire protection
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hydrate". A list of authors is available in Wikipedia.