ljósefni

Ljósefni is the Icelandic term historically used to refer to luminous substances, especially elemental phosphorus and related compounds. The name is formed from ljóss meaning light and efni meaning substance, reflecting the material’s tendency to emit light under certain conditions.

Phosphorus is a nonmetal element essential for life, occurring in DNA, ATP, and bones, and existing in phosphate minerals. In industry, phosphorus is produced from phosphate rock by reducing it with carbon at high temperatures to yield white phosphorus, which can be converted into red or black allotropes.

Ljósefni has several allotropes. White phosphorus is a waxy, highly reactive allotrope that glows faintly in the dark. Red phosphorus is more stable and used in safety matches and flame retardants. Black phosphorus forms a layered structure and shows semiconducting properties.

Applications include phosphate fertilizers, detergents, and steel production, as well as flame retardants and specialty materials.

Safety and handling are critical: white phosphorus is highly toxic and can cause severe damage; it is stored under water or in inert environments to prevent contact with air. Regulation and proper industrial controls are essential in production and use.

Historically, phosphorus was first isolated in 1669 by Hennig Brand, who heated urine to produce a glow. The term phosphorus derives from Greek and was adopted in Icelandic contexts as ljósefni to describe luminous forms of the element and related compounds.