Lime is a general term for
calcium-containing
inorganic materials, in which
carbonates,
oxides and
hydroxides predominate. Strictly speaking, lime is
calcium oxide or
calcium hydroxide. It is also the name for a single mineral (native lime) of the CaO composition, occurring very rarely.
[1] The word "lime" originates with its earliest use as building mortar and has the sense of "sticking or adhering."
[2] Lime can also refer to a sticky substance (
birdlime) smeared on branches to catch small birds.
These materials are still used in large quantities as building and engineering materials (including
limestone products,
concrete and
mortar) and as
chemical feedstocks, among other uses. Lime industries and the use of many of the resulting products date from
prehistoric periods in both the
Old World and the
New World.
The rocks and minerals from which these materials are derived, typically
limestone or
chalk, are composed primarily of
calcium carbonate. They may be cut, crushed or pulverized and chemically altered. "Burning" (
calcination) converts them into the highly
caustic material
quicklime (calcium oxide, CaO) and, through subsequent addition of water, into the less caustic (but still strongly
alkaline)
slaked lime or
hydrated lime (
calcium hydroxide, Ca(OH)
2), the process of which is called
slaking of lime.
When the term is encountered in an agricultural context, it probably refers to
agricultural lime. Otherwise it most commonly means
slaked lime, as the more dangerous form is usually described more specifically as
quicklime or
burnt lime.
The limestone quarry at Akselberget, Brønnøy, Norway
Lime production process
Quicklime is produced according to the reaction: CaCO3 + heat → CaO + CO2. Lime is used extensively for waste water treatment with ferrous sulphate.
- Quicklime can be hydrated, i.e., combined with water.
Hydrated lime, known as slaked lime, is produced according to the reaction: CaO + H2O → Ca(OH)2
See alsoReferences
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