phosphorus fŏs´fərəs [key] [Gr.,=light-bearing], nonmetallic chemical element; symbol P; at. no. 15; at. wt. 30.97376; m.p. 44.1°C; b.p. about 280°C; sp. gr. 1.82 at 20°C; valence −3, +3, or +5. Solid phosphorus has a tetratomic molecule (P4) with molecular weight 123.8952 atomic mass units (amu). Phosphorus was discovered c.1674 by Hennig Brand of Hamburg, an alchemist, who prepared it from urine. Phosphoric acid was discovered in 1770 by K. W. Scheele and J. G. Gahn in bone ash (see ash); Scheele later isolated phosphorus from bone ash (1774) and produced phosphoric acid by the action of nitric acid on phosphorus (1777).
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