What is red phosphorus

Red phosphorus is one of the allotropes (different structural forms) of elemental phosphorus. It is a less reactive and more stable form of phosphorus than white phosphorus, which is another common allotrope of elemental phosphorus. Red phosphorus gets its name from its colour, which can range from deep red to violet or even black, depending on its preparation and impurities.

What is red phosphorus

Major characteristics and uses of red phosphorus include:

  • Stability: Unlike white phosphorus, which is highly reactive and can spontaneously ignite in air, red phosphorus is relatively stable and does not spontaneously ignite. This property makes red phosphorus much safer to handle and store.

  • Structure: The structure of red phosphorus consists of networks or chains of phosphorus atoms. This arrangement makes it less reactive because the atoms are more tightly bound and less susceptible to spontaneous combustion.

  • Preparation: Red phosphorus is usually prepared by heating white phosphorus in the presence of an inert gas or by exposing white phosphorus to light, which triggers a slow transformation of white phosphorus into the red allotrope. This process is called "red phosphorus conversion".


  • Matchstick Tips: The most famous use of red phosphorus is in striking the surface of safety matches. The striking surface contains red phosphorus and other compounds that facilitate ignition when the matchbox is rubbed against it.
  • Flame Retardant: Red phosphorus is used as a flame retardant in a variety of materials including plastics and textiles. It can reduce the flammability of these materials by releasing phosphoric acid when exposed to heat or flame, which can help suppress combustion.
  • Pharmaceuticals and Chemical Reactions: Red phosphorus is used as a reagent in some chemical reactions and can be employed in the synthesis of various organic compounds.

Overall, red phosphorus is valued for its stability and safety, making it useful in applications where the more reactive white phosphorus would be hazardous.