phosphorus

phosphorus

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Minerals of phosphorus:
Phosphorite or phosphate rock –  [ Ca₃ (PO₄)_{2 ]}

Fluor apatite –  [ 3Ca₃(PO₄)₂ . CaF_2]

Chlor apatite –  [3Ca₃(PO₄)₂ . CaCl_2]

Extraction of white phosphorus:

There are two method for extraction—
Retort process: (How can you prepare white P  from phosphate rock?)
Bone ash is heated with H₂SO₄ then  orthophosphoric acid is obtained which on strong heating gives  metaphosphoric acid.
Ca₃(PO₄)₂ + 3H₂SO₄ ——-> 2H₃PO₄ + 3CaSO₄
H₃PO₄ ——> HPO₃ (meta phosphoric acid) +  H₂O

Meta phosphoric acid  is mixed with coke and then distilled.

4HPO₃ +  10 C ——>  2H₂O + P₄  (phosphorus (white))+ 10 CO

Vapors of phosphorus are condensed in water. White P is insoluble in H₂O  therefore it settles down in the form of solid.
Electro-thermal process:
Mixture of calcium phosphate, silica and coke is heated in an electric furnace. Electric furnace contains carbon electrode. On passing current temperature rises  upto 1500^o C and following reactions takes places:-
Ca₃(PO₄)₂  (bone ash) + 3SiO₂ ——–> 3 CaSiO₃ (slag) + P₂O₅
2  P₂O₅ + 10C —–> P₄ (white phosphorus) + 10CO

Calcium silicate is removed as slag. The vapors of  phosphorus are condensed in water. White P is insoluble in  H₂O. Therefore it settles down in the form of solid.

Allotropes  of  phosphorus:

It  exists in the following  allotropic  forms :
1) white or yellow P
2) Red P
3) Violet P
4) Black P
5) Scarlet P

source : 2012 Book Archive

Physical properties :

1. White P(is called phosphorus) is colorless, soft and wax like solid. It can be cut by a knife. It turns yellow on long standing.
2. It has garlic like odor.
3. It is insoluble in H₂O but soluble in benzene, chloroform, ether, alcohol ,  CS₂.
4. Ignition temperature of white P is   30⁰C. Therefore it catches fire immediately in air.
5. On burning in air it forms poisonous fumes of  P₂O₅. Therefore it is   kept in water.
6. It is poisonous in nature. Vapors of P are injurious to health . Persons working in the factory of phosphorus develop a disease  ‘phossy  jaw’.
7. Melting point of white P is 44^o C and boiling point is 287 ^oC.