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 colorless 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 pent oxide. When exposed to sunlight, or when heated in its own vapor 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 vapor pressure of 1 atmosphere at 417°C.
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