The high re activity of white phosphorus is believed to be the result of the strain in the p4 molecular: The p-p bonds are compressed in the tetrahedral structure. Whited phosphorus was once used in the manufacture of matched, but because of its toxicity it has been replaced by tetra-phosphorus trisulfied, P4S3.
When heated in the absence of air, white phosphorus is slowly converted to red phosphorus at about 300C