Efflorescence

Encyclopedia : E : EF : EFF : Efflorescence

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Effloresce redirects here, for the album by Oceansize, see Effloresce (album).

Efflorescence, in chemistry, is the loss of water of crystallization from a hydrated salt to the atmosphere on exposure to air.

Examples

1. A 5 micrometre aqueous droplet of NaCl will spontaneously crystallize at 45% relative humidity (298 K) to form a NaCl cube by the mechanism of homogeneous nucleation. The original water is released to the gas phase.
2. Gypsum (CaSO_{4.2H2O) is a hydrate solid that, in a sufficiently dry environment, will give up its water to the gas phase and form anhydrite (CaSO4).}
3. Bluestone (CuSO_{4.5H2O) is a blue crystalline solid that when exposed to air, slowly loses water of crystallization from its surface to form a white layer of anhydrous copper(II) sulfate.}

Masonry Usage

Efflorescence occurs in masonry construction, particularly brick, when water moving through a wall or other structure brings natural salts to the surface. The resulting white deposits are commonly referred to as "efflorescence" in this instance.

See also

• Deliquescence

 

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