Red phosphorus

Red phosphorus is the common name of several forms of elemental phosphorus, often considered one of its allotropes. Its most common shape is an amorphous polymeric red solid that is stable in air. Amorphous red phosphorus is easily obtained when exposing white phosphorus to sunlight or heating, which was discovered in 1847 by Anton von Schrötter. When sublimed in a vacuum, amorphous red phosphorus can transform into a crystalline form, known either as violet or Hittorf's phosphorus, after the name of its discoverer. When this process is carried out in the presence of iodine, another crystalline is obtained alongside it, called fibrous red phosphorus. Applications of amorphous red phosphorus include matches and fire retardants.