116: Phosphorus

HISTORY AND EPIDEMIOLOGY

Phosphorus is a nonmetallic element not naturally found in its elemental form; it was isolated from distilled urine by Hennig Brandt in 1669. White phosphorus has been used in munitions (mortar rounds, grenades, artillery shells, bombs) since World War I for its antipersonnel effect as well as its warning, incendiary, and smoke producing properties. It is also used in fireworks made in countries other than the United States and China and for selected chemical synthetic processes (including some pesticides). White phosphorus was used extensively in the past as a rodenticide but is no longer employed for this purpose in the United States. Because of the potential use of red phosphorus for illicit drug manufacture (methamphetamine), its sale is monitored by the US Drug Enforcement Administration, which limits its availability in the United States. Before modern regulation, it was used in scientifically unsubstantiated remedies primarily because its phosphorescent and reactive qualities suggested potency. Its occasional use for homicides was limited by its glowing, smoking qualities. It remains a common method of suicide in some countries.

At the beginning of the 20th century, phosphorus was used in millions of “strike anywhere” matches (lucifers). However, safety concerns with the matches and illnesses in the workers producing the matches prompted a shift from using the more dangerous white phosphorus in the match heads to substituting the safer red phosphorus in the strikers. Workers chronically exposed to white phosphorus developed “phossy jaw,” an illness characterized by disfiguring osteonecrosis of the mandible along with multiple draining abscesses.

CHEMISTRY

Phosphorus, atomic number 15, is in a group of 15 nonmetallic elements sharing chemical properties with nitrogen (above) and arsenic (below) in the periodic table. Elemental phosphorus can exist in several different allotropes (polymorphs); the two common forms considered here are red phosphorus and the highly reactive white phosphorus. The relatively nontoxic and nonreactive black form will not be considered further.

White phosphorus is a waxy whitish to yellow solid with a melting point of 111.4°F (44.1°C). Often there is a small amount of red phosphorus in samples of white phosphorus, resulting in discoloration and explaining the term, “yellow” phosphorus. The word “phosphorus” means light-bearer, which originates from its property of glowing when exposed to air, due to the formation of reactive luminescent phosphorus oxides on its surface. Phosphorus is insoluble in water and often stored under it, but soluble in carbon disulfide and other organic solvents. White phosphorus is very reactive, igniting spontaneously in air at approximately 93°F (34°C), oxidizing to form phosphorus pentoxide (P₄O₁₀), which usually appears as a white fume having a garliclike smell. Phosphorus pentoxide is hydroscopic and reacts with water to form phosphoric acid (H₃PO₄) and reacts with organic molecules in dehydrating reactions.

Red phosphorus is a red powdery compound of limited toxicologic significance. It is ...