ydrates . Compounds of addition of water to many substances, generally salts. The water in a hydrate is called water of hydration and, more frequently, water of crystallization.
Summary
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- 1 Hydrate
- 1 Inorganic chemistry
- 2 Uses of hydrates
- 2 Sources
Hydrate
Hydrate is a term used in organic chemistry and inorganic chemistry to indicate that a substance contains water. They are defined compounds and not more or less wetted substances, because their composition is constant regardless of the preparation method and the size of the crystals and because the reaction between the number of moles of the anhydrous salt and that of the combined water is a fraction very simple.
Inorganic chemistry
In inorganic chemistry, hydrates contain water molecules that are either bound to a metal core or crystallized with the metal complex. Such hydrates are said to possess “water of crystallization” or “water of hydration”. This is released when the hydrate is subjected to high temperature, the network breaks and one or more water molecules escape.
When a salt forms more than one hydrate, the law of multiple proportions is fulfilled . In the hydrate, water maintains its molecular structure practically unchanged by being linked to the anhydrous compound through covalent bonds coordinated through one of the lone electron pairs of the oxygen atom, and sometimes maintains hydrogen bridge bonds. In the case of electrovalent type compounds, water is bound to one of the ions, preferably to the cation.
Uses of hydrates
- Building:
The presence of hydrates is absolutely useful in all three fields of effort. Generally, in construction and refractories, inorganic binders are often deprived of water during manufacturing. For example, both in cement and plaster products, heat is applied to raw materials. Once water is added to a construction site, the powder can rehydrate and form bonds with other substances that are present. Thus, one goes from powder, to mixture, or rubber and then forms “cement stone”. Water that is not chemically limited, or converted into hydrates, may again come out as steam, especially due to heat of hydration, with cement products in particular, which undergo exothermic chemical reaction with water.
Generally, the longest can keep cementitious products wet immediately after placement, the better. The more wet cement products are kept, the more water will be converted into hydrates, instead of evaporation due to the heat of hydration and other environmental influences. Premature dryness is a cause for severe concrete problems, such as cracking and shrinking.
- Passive Fire Protection (PFP):
Avoiding premature drying is important to the rest of the building’s cement products, it particularly sprays fireproofing and firestop mortars, where the slightest cracking can lead to rejection. Chemically bound water is used up by endothermic reactions when exposed to heat from fire. Fire temperatures in a building can reach 1100 ° C, depending on the fuel present and oxygen availability, only the hydrates keep the temperature of the item at or below 100 ° C until all the water is gone.
Therefore, the more hydrates, the longer the duration of fire resistance. This is what lends fire-resistive characteristics to basic, or “old” construction materials, such as plaster, concrete or plaster. The duration of fire resistance is important for many high-tech PFP products such as flame retardant and endothermic paints, coats and tiles, such as those used in space physics for re-entry vehicles.
