German alchemist Hennig Brand discovered phosphorous in 1669 when he strongly heated the residue left by the evaporation of urine. He observed the striking blue-green light that is emitted by phosphorus vapour when it comes in contact with air. The urine residue contained organic compounds and phosphate. When it was heated, the organic compounds were decomposed.
Phosphorus is too reactive to occur in nature in the free state. Most of the phosphorus in the earth’s crust occurs as phosphate rock. Two of these phosphate rock minerals are hydroxyapatite and fluorapatite. Hydroxyapatite is the main constituent of the bones and teeth of animals. When water is fluoridated, fluorapatite replaces the hydroxyapatite in teeth enamel. Fluorapatite is more resistant to attack by acids, thereby helping to prevent dental cavities.
Phosphate groups are an essential part of the structure of DNA, the storehouse of genetic information, and they play a vital role in the transfer of energy in our bodies. Thus phosphorus is an essential component in our diet.
