A strange and dangerous glow – White phosphorous

What does it look like?

White phosphorous consists of tetrahedral P4 molecules in which each phosphorous atom is bonded to the three other atoms of the tetrahedron. The P4 molecule exists in the solid, liquid or gas-phase up to temperatures of 800 °C, and in the solid phase exists in a low temperature b-phase or high temperature a-phase that differ in the relative orientation of the P4 tetrahedra. White phosphorous is soft and waxy, insoluble in water and glows in the dark.

The strange group of phosphorus

The strange group of phosphorus

Where did the structure come from?

Discovered around 1669 by the alchemist Hennig Brand during his search for the elusive “philosopher’s stone” and whilst heating the “golden stream” (urine) with charcoal at very high temperatures, Brand obtained glowing fumes and an unusual white solid that burned and glowed with an eerie pale-green light.

The structure of white phosphorous was first reported by G. Natta and L. Passerini in 1930.

What is it?

White phosphorous, is the most important of the four allotropes of phosphorous (the others being red, violet and black). Like the allotropes of carbon (such as Graphite, buckyballs and diamond), these materials differ in their crystal structure but are made up of the same element.   The chemiluminescent glow of white phosphorous is due to the slow oxidation of its vapours with air, is highly flammable and pyrophoric (self-igniting). For this reason, white phosphorous was once used in parlour tricks, matches fireworks and by military forces in incendiary bombs. Workers who produced matches and inhaled white phosphorous vapours often developed “Phossy jaw”, or dissolving of the jaw bone, while contact with the hot liquid causes burning deep into tissue. The use of white phosphorous was banned in matches in 1906, and in incendiary weapons against civilians in 1980.

Today, around 850 000 tonnes of white phosphorous are produced for peaceful uses, namely as a raw material for the production of phosphoric acid, pharmaceuticals and fertilisers.

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