Laboratory Preparation of Phosphorus Trioxide

Phosphorus trioxide (P₂O₃ or P₄O₆) is obtained by the combustion of phosphorus in a limited supply of air.

4P + 3O₂ → 2P₂O₃

Physical properties

• It is a white waxy substance
• It has a garlic odour.

Chemical properties

1. It reacts with cold water, gives phosphorus acid.

P₂O₃ +3H₂O → 2H₃PO₃

2. It reacts with hot water vigorously to form inflammable phosphine.

2P₂O₃ + 6H₂O → PH₃ ↑ + 3H₃PO₄