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Properties of Phosphorus

Phosphorus was discovered in 1869. Phosphorus inevitably occurs as a phosphate. Phosphate minerals, i.e., phosphorite, fluorapatite, ferric phosphate and bone-ash (which consists principally of calcium phosphate), are important sources of phosphorus.

Phosphorus is an essential constituent of all living things. In many plants and animal tissues it is found as phosphoproteins.

Phosphorus exists in several forms. Of these, white and red varieties are the most familiar ones.

  1. White Phosphorus

    • White phosphorus is a soft, waxy white solid, and is very poisonous. On exposure to light it rapidly becomes yellow. White phosphorus is soluble in benzene, carbon disulphide, and sulphur chloride. It undergoes spontaneous oxidation in contact with air giving a faint green glow. It ultimately bursts into flame as the temperature rises. White phosphorus also explodes in contact with liquid bromine. Heating with caustic soda solution leads to the formation of phosphine, which is a colorless gas used as a pesticide, and alkali hypophosphite. It dissolves in concentrated nitric acid yielding phosphoric acid.

    Red Phosphorus

    • Red phosphorus is a reddish violet powder. It is tasteless, odorless, and nonpoisonous. It is a feeble conductor of electricity. Red phosphorus melts at 582.5 degrees Celsius under pressure. Red phosphorus is much less chemically reactive than white phosphorus. It does not ignite in air below 260 degree C. It is insoluble in water, alkali, hydroxide solutions, carbon disulphide, and ether. It does dissolve in concentrated nitric acid. It burns in chlorine only when heated, but quietly burns in contact with liquid bromide. It combines with iodine on heating.

    Violet Phosphorus

    • Violet phosphorus is obtained by heating molten phosphorus at 240 to 260 degrees C either alone or in the presence of catalysts like iodine. It is a nonconductor of electricity and has a rhombohedral crystal structure.

    Black Phosphorus

    • Black phosphorus, also called metallic phosphorus, is a crystalline black compound. It resembles graphite. Black phosphorus is a good electrical conductor. It is soluble in carbon disulphide.

    Types of White Phosphorus

    • Two varieties of white phosphorus are known as ?-white phosphorus, which consists of cubic crystals and ?-white phosphorus, a hexagonal crystal.

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