Phosphorus P

Discovery

Phosphorus was the first element to be discovered by a named individual in recorded history. In 1669 the Hamburg merchant and alchemist Hennig Brand, searching for the philosopher's stone, boiled down large quantities of urine, heated the residue strongly and collected a white, waxy substance that glowed in the dark and burst into flame in air.

Brand kept his method secret, but Johann Kunckel and Robert Boyle soon worked out how to make phosphorus themselves. In the 1770s Carl Wilhelm Scheele and Johan Gottlieb Gahn showed that bones contain phosphorus, and Scheele developed a way to make it from bone ash, which became the standard source for a century. Lavoisier listed phosphorus among the elements in the 1770s and 1780s. Later, phosphate rock mined from large deposits replaced bones as the raw material.

Origin of the name

The name comes from the Greek phosphoros, 'light-bearer', the old name for the planet Venus as the morning star, because white phosphorus glows faintly in air. The symbol is P.

Main uses

• Fertilisers: most mined phosphate rock is turned into phosphoric acid and then into fertilisers, which are essential for modern crop yields.
• Food and drink: phosphoric acid gives cola drinks their tang, and phosphates act as leavening agents and preservatives.
• Matches: the striking surface of safety matches contains red phosphorus.
• Batteries: lithium iron phosphate is a widely used, thermally stable battery cathode material.
• Chemicals: flame retardants, water treatment, metal finishing and pesticides.

Isotopes

Phosphorus has one stable isotope, phosphorus-31, which makes phosphorus NMR a powerful tool for studying living tissue and chemical compounds. The radioactive phosphorus-32 (half-life about 14.3 days) and phosphorus-33 (about 25 days) are used to label DNA and proteins in molecular biology research. Phosphorus-32 has also been used in medicine to treat certain blood disorders.

In everyday life

An adult body contains roughly 0.7 kilograms of phosphorus, mostly as calcium phosphate in bones and teeth. It is found in almost all foods, especially dairy, meat, fish and beans, so dietary deficiency is rare.

White phosphorus is highly toxic and ignites spontaneously in air, so it is stored under water. Phosphate runoff from farms and wastewater can trigger algal blooms in lakes, and because phosphate rock reserves are concentrated in a few countries, recycling phosphorus from waste is an area of active research.