phosphorus

Phosphorus

source : slide player

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

Fluor apatite –  [ 3Ca3(PO4)2 . CaF2]

Chlor apatite –  [3Ca3(PO4)2 . CaCl2]

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 1500o 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

p-4

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 44o C and boiling point is 287 oC.