MISCELLANEOUS AND USEFUL CHEMICAL COMPOUNDS (Part-IV)

Calcium sulphate dihydrate (CaSO₄·2H₂O) is also called gypsum. It is heated to 393K to produce plaster of Paris (CaSO₄·½H₂O) which is used in the building industry as well as plaster for broken bones.

Disproportionation reactions are a special type of redox reactions. Using this reaction, household bleaches are obtained using sulphur, phosphorous, and chlorine.

Phosphorus reacts very quickly with oxygen in the air and starts burning. This also means that its ignition temperature is very low. For these reasons, it is kept immersed in water, because it is not soluble in water.

White phosphorus is a very flammable substance that ignites rapidly in the air. It is insoluble in water. Therefore, white phosphorus is kept in water to avoid contact with air.

White phosphorus is an allotrope of phosphorus, found in the common tetra phosphorus (P4) molecular form. White phosphorus is more reactive than other allotropes of phosphorus. When left open in the air, it starts burning soon.

Phosphine (PH3) or hydrogen phosphide gas is a toxic gas that results from the anaerobic decay of phosphorus-containing organic materials. It has an odor similar to that of garlic or decaying fish.

Heating limestone or calcium carbonate (CaCO₃) is a decomposition process. In this, carbon dioxide (CO₂) is liberated, and calcium oxide (CaO) is formed.

The presence of hydrogen sulfide (H₂S) gas and other sulfur compounds in the air causes the sulfidation of silver, which reduces its luster. This is called the corrosion of silver.

Biofertilizers produce a range of micro-organisms in the soil that are capable of converting atmospheric nitrogen into nitrates. Biofertilizers, especially algae, have the ability to hold water and are also non-polluting and renewable.

Animals and plants are easily decomposed by anaerobic micro-organisms in the presence of wastewater. Gases like methane, carbon dioxide, hydrogen, hydrogen sulfide, ammonia, etc., are produced in this process. This mixture of gases is called biogas. A biogas plant is a unit that converts organic waste material (living biomass) into useful gaseous fuels (methane and carbon dioxide) and organic manure as a liquid by-product.