Calcium carbonate Three types of calcium carbonate-containing rock are excavated and used by industry. They are limestone, chalk and dolomite. Limestone and chalk are both forms of calcium carbonate and dolomite is a mixture of calcium and magnesium carbonates. All have impurities such as clay but some rocks are over 97% pure. Limestone and other products derived from it are used extensively in the construction industry and to neutralize acidic compounds in a variety of contexts. In the chemical industry, large quantities of limestone are heated to ca 1500 K to form calcium oxide, known as quicklime: Water can be added to lime to form calcium hydroxide. The process is known as 'slaking'. Solid calcium hydroxide is known as slaked lime or hydrated lime, and solutions and suspensions in water as milk of lime. The term lime is often used to cover quicklime, slaked lime (hydrated lime) and milk of lime. For a particular use, an appropriate choice is made from the four: limestone, quicklime, slaked lime or milk of lime. In many uses, lime reacts more quickly than limestone but is more expensive, because a high temperature is required to produce it from limestone. Uses of limestone and lime
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Calcium carbonate
Three types of calcium carbonate-containing rock are excavated
and used by industry. They are limestone, chalk and dolomite. Limestone and
chalk are both forms of calcium carbonate and dolomite is a mixture of calcium
and magnesium carbonates. All have impurities such as clay but some rocks
are over 97% pure. Limestone and other products derived from it are used
extensively in the construction industry and to neutralize acidic compounds in a
variety of contexts.
In the chemical industry, large quantities of limestone are heated to ca 1500 K
to form calcium oxide, known as quicklime:
Water can be added to lime to form calcium hydroxide. The process is known
as 'slaking'. Solid calcium hydroxide is known as slaked lime or hydrated lime,
and solutions and suspensions in water as milk of lime.
The term lime is often used to cover quicklime, slaked lime (hydrated lime) and
milk of lime.
For a particular use, an appropriate choice is made from the four: limestone,
quicklime, slaked lime or milk of lime. In many uses, lime reacts more quickly
than limestone but is more expensive, because a high temperature is required
to produce it from limestone.
Uses of limestone and lime
Figure 1 Principal uses of limestone and lime.
The principal uses, by far, of limestone and lime are in the construction
industry and cement making. They are also used in the chemical and
metallurgical industries and in agriculture.
On a worldwide basis, the proportions of lime used in different industries are:
60% metallurgy (mainly steel manufacture, slag formation and its use in the blast
furnace)
25% construction (for example, it is used with asphalt in road paving, to
stabilize soils and in making mortar and plaster)
15% for chemical and industrial uses (for example to make bleaches used in
the manufacture of paper, to make precipitated calcium carbonate, a fine powder
used in coatings for paper and paints, and in refining sugar to remove colloidal
impurities) and for environmental uses (for example, with soda ash by both
municipal authorities and industry, to soften water (remove calcium and