Question

Describe the preparation of red phosphorus.

Answer 1

1. Heat white (yellow) phosphorus at 525 K in an inert atmosphere.
2. Use a cast iron retort with thermometer jackets and a safety valve.
3. Add a small amount of iodine to speed up the conversion.
4. Replace air in the retort with inert gas like carbon dioxide.
5. Heat carefully without exceeding 525 K for several hours.
6. Cool the retort; red phosphorus forms as a hard mass.
7. Powder and boil with caustic soda to remove any white phosphorus.
8. Wash thoroughly and dry the red phosphorus obtained.