In chemistry, calcium hydroxide is known as slaked limestone. It is an inorganic compound with the formula Ca(OH).
When mixed with water, quicklime (calcium dioxide) forms a white or colourless powder. Other names include hydrated lime (calcium oxide), caustic lime (builders’ lime), slaked limestone, cal and pickling powder. It has a number of uses, including in food preparation. The E number is E526.

Continue reading to find out more about its composition, preparation, properties and chemical reactions.

Calcium Hydroxide
Lime water is a saturated solution of calcium hydroxide, also known as milk or lime. The calcium ion and the calcium ion’s (Ca2+) ionic bond interactions
Two hydroxide ions (OH) are also present.
( ) holds calcium hydroxide molecule together. This substance is hazardous for humans. It can cause chemical burns and skin irritation.

Concentrated Ca(OH2)2
Exposure can lead to lung damage, and even blindness. Like all metal hydroxides it has a polymeric composition. Calcium hydroxide, an industrial alkali, is also used in mortars, cements and plasters. It is used in the manufacturing of kraft paper as well as flocculant for sewage treatment.

Calcium Hydroxide Structure

Calcium and hydroxide are in their ionic form Ca2+, so the bond is ionic.
OH-
Ions have ionic bonding. The calcium metal ion also has two hydroxide bonds.

Like all metal hydroxides it has a polymeric structural. The structure is the same as that of Mg (OH)2.
The cadmium-iodide motif can be seen in the structure (brucite). Strong hydrogen bonds are present between the layers.

In the lab, it can be produced by mixing aqueous calcium chloride solutions with sodium hydroxide. Portlandite is a rare mineral that can be found only in certain volcanic, plutonic and metamorphic rock types. The substance has been found in coal-burning dumps. It is available as white powder or colorless crystals.

Preparation Calcium Hydroxide
Commercially, calcium hydroxide can be prepared by mixing lime with water.

CaO+H2O-Ca(OH)2
In the lab, it can be produced by mixing aqueous calcium chloride solutions with sodium hydroxide. Portlandite is a rare mineral that can be found in volcanic, plutonic and metamorphic rock. The mineral has been found in coal wastes that are being burned.

Calcium Hydroxide: Properties
Below we discuss some of the main physical and chemical characteristics of high quality calcium hydroxide products.

Physical Properties

Physical properties are the measure of how a substance behaves at a molecular scale. It includes its melting and boiling points, as well as density.

Calcium hydroxide has a powdery, soft, crystalline texture with an bitter taste.
The density of calcium hydroxide is 2.211g/cm3. It has a molecular weight of 74.093g/mol.
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The melting point for calcium hydroxide is 853K.
The solubility of calcium hydroxide in water decreases with increasing temperature.
At room temperature, calcium hydroxide will dissolve in pure water to produce an alkaline solution that has a pH value of 12.4. Calcium hydroxide can cause chemical burns. The reaction between calcium hydroxide and carbon dioxide produces calcium carbonate CaCO3.
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Chemical Properties

Chemical properties are the changes that a substance undergoes in terms of both physical and chemical nature.

Calcium carbonate is formed when carbon dioxide passes through lime water. This causes the water to become milky.
Ca(OH)2+CO2-CaCO3+H2O
Calcium hydrogen carbonate is formed when the precipitate dissolves excess carbon dioxide.
CaCO3+CO2+H2O-Ca(HCO3)2
Hypochlorite, a component in bleaching powder, is formed when milk of lime and chlorine combine.
2Ca(OH)2+2Cl2-CaCl2+Ca(OCl)2+2H2O
Salts are formed when lime water reacts to acids.
A saturated solution of Calcium Hydroxide in Water also reacts and dissolves metals like aluminium.
Water is only marginally soluble. Calcium hydroxide, on the other hand, is highly soluble both in glycerol or acids. It is a mild acid base when dissolved to saturation in water.

Calcium Hydroxide Uses
Due to its basic properties, calcium hydroxide is used in a wide range of applications. Here are a few of them.

Uses include whitewash, plaster, and mortar.
In the tanning process, it is used to remove hairs from hides.
In medicine, it is used to treat acidic burns as well as an antacid.
In the treatment of sewage, calcium hydroxide can be used as a flocculant or clarifying agent.
This chemical can also be used to modify pH because of its simplicity.
In the manufacture of polymers, calcium hydroxide is a key component.
Nair is a depilatory chemical agent.
Calcium supplement in infant formulas fortified with minerals
Chemical reagent used to make a fungicide with a long lasting effect.
Use in the tanning industry to neutralize acid, lime hides and skins and flocculate wastewater.
Calcium stearate is made in the chemical industry.
In the food industry, it is used to treat water in alcoholic and soft drink beverages.
Sugar cane is separated from sugar by using this method.
Use for gas analysis and carbon dioxide analysis. Use to remove hair from the leather, to act as a pesticide and to treat water.
During root canal procedures, calcium hydroxide can be used to fill in cavities.
Calcium hydroxide is used to remove carbon dioxide due to its interaction with carbon dioxide.