Phosphorus

Phosphorus: the essentials

 Brief description: phosphorus is commonly misspelled "phosphorous". It is an essential component of living systems and is found in nervous tissue, bones and cell protoplasm. Phosphorus exists in several allotropic forms including white (or yellow), red, and black (or violet). White phosphorus has two modifications. Ordinary phosphorus is a waxy white solid. When pure, it is colourless and transparent. It is insoluble in water, but soluble in carbon disulphide. It catches fire spontaneously in air, burning to P₄O₁₀, often misnamed as phosphorus pentoxide. When exposed to sunlight, or when heated in its own vapour to 250°C, it is converted to the red variety. This form does not ignite spontaneously and it is a little less dangerous than white phosphorus. The red modification is fairly stable and sublimes with a vapour pressure of 1 atmosphere at 417°C.

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Isolation

Isolation: originally, phosphorus was extracted from urine. However there is plenty of phosphorus in phosphate ores and those ores represent the usual source for commercially produced phosphorus. There is normally no need to make phosphorus in the laboratory as it is readily available commercially.

The usial route involves heating a phosphate with sand and carbon in an electric furnace. It is highly energy intensive.

2Ca₃(PO₄)₂ + 6SiO₂ + 10C (1500°C) → 6CaSiO₃ + 10CO + P₄

The reaction may proceed via "phosphorus pentoxide", P₄O₁₀.

2Ca₃(PO₄)₂ + 6SiO₂ + → 6CaSiO₃ + P₄O₁₀

P₄O₁₀ + 10C → 10CO + P₄

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