Calcium hydroxide: properties and applications

Ca (OH) 2 is calcium hydroxide (from the Latin Calcium hydroxide), it is a fairly common chemical substance. It is by nature considered a strong foundation. It is a fine-grained powder of yellowish color or colorless crystals. It is able to decompose on heating, resulting in the release of calcium oxide. It is poorly soluble in water. In this case, the aqueous solution of calcium hydroxide is, by its chemical properties, the middle base. In the presence of metals, it can release hydrogen, which is recognized as an explosive gas.

Calcium hydroxide when ingested through the mouth or as a result of inhalation of aerosol can be absorbed into the tissues and accumulate in them. At normal room temperature of 20-22 degrees, this substance is practically not evaporated, but when spraying its particles can be dangerous to health. Getting on the skin, in the respiratory tract or mucous membranes of the eyes, calcium hydroxide has an irritating, even corrosive effect. Prolonged contact with the skin can cause dermatitis. Also, pulmonary tissue can be affected by the constant action of calcium hydroxide particles.

This chemical compound has many trivial names, such as slaked lime (it is obtained by the method of calcium oxide quenching with ordinary water), lime water (it is a clear aqueous solution). Other names: cotton powder (calcium hydroxide as a dry powder) and lime milk (a saturated aqueous suspension). Often, quicklime or lime is also commonly called calcium oxide.

Calcium hydroxide, whose chemical properties are considered to be aggressive towards other substances, are obtained by the method of quenching lime, that is, as a result of the interaction (chemical reaction) of calcium oxide and water. Schematically, this reaction looks like this:

CaO + H2O = Ca (OH) 2

The resulting aqueous solution is characterized by an alkaline reaction of the medium. Like all typical hydroxides, calcium hydroxide reacts with:

1. Inorganic acids with the formation of typical calcium salts

H2SO4 + Ca (OH) 2 = CaSO4 + 2H2 O

2. Carbon dioxide, which is dissolved in water, so the aqueous solution very quickly becomes turbid in the air, and a white insoluble precipitate is formed-calcium carbonate

CO2 + Ca (OH) 2 = CaCO3 + H2O

3. Carbon monoxide when the temperature rises to 400 degrees Celsius

CO (t °) + Ca (OH) 2 = CaCO3 + H2

4. With salts, the result is also a white precipitate - calcium sulphate

Na2SO3 + Ca (OH) 2 = CaSO3 + 2NaOH

The use of calcium hydroxide is very popular. For sure, everyone knows that lime is treated with walls of premises, trunks of trees, and also use it as a component of a mortar of mortar. The use of calcium hydroxide in construction has been known since ancient times. And now it is included in the plaster, it produces silicate brick and concrete, the compositions of which are almost identical with the mortar. The main difference is in the method of preparation of these very solutions.

Calcium hydroxide is used to soften water hardness, to make bleach, lime inorganic fertilizers, causticize potassium carbonate and sodium. Also, this substance is indispensable in the tanning of leather in the textile industry, in the preparation of various calcium compounds, as well as to neutralize acidic solutions, and sewage including. On its basis, organic acids are produced.

Calcium hydroxide has found its application in the food industry, where it is better known as food additive Е526, used as an acidity regulator, hardener and thickener. In the sugar industry, it is used for desalting molasses.

In laboratory and demonstration experiments, lime water is an indispensable indicator of carbon dioxide detection during the course of chemical reactions. Lime milk is used to treat plants for the control of diseases and pests.