phosphorus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A highly reactive, poisonous, nonmetallic element occurring naturally in phosphates, especially apatite, and existing in three allotropic forms, white (or sometimes yellow), red, and black. An essential constituent of protoplasm, it is used in safety matches, pyrotechnics, incendiary shells, and fertilizers and to protect metal surfaces from corrosion. Atomic number 15; atomic weight 30.9738; melting point (white) 44.1°C; boiling point 280°C; specific gravity (white) 1.82; valence 3, 5. See Table at element.
2. n. A phosphorescent substance.

Century Dictionary and Cyclopedia

1. n. [capitalized] The morning star; Phosphor.
2. n. Chemical symbol, P; atomic weight, 31; specific gravity, 1.826. A solid non-metallic combustible substance, hitherto undecomposed, not found by itself in nature, but occurring chiefly in combination with oxygen, calcium, and magnesium. It is widely distributed, being an essential constituent of all plants and of the bony tissue of animals. It was originally obtained from urine; but it is now manufactured from bones, which consist in large part of calcium phosphate. Common phosphorus, when pure, is semi-transparent and colorless. At common temperatures it is a soft solid, easily cut with a knife, the cut surface having a waxy luster; at 108°F. it fuses, and at 550° is converted into vapor. It is soluble, by the aid of heat, in naphtha, in fixed and volatile oils, and in sulphur chlorid, carbon disulphid, and phosphorus sulphid. It is exceedingly inflammable. Exposed to the air at common temperatures, it undergoes slow combustion, emits a white vapor of a peculiar garlic odor, and appears luminous in the dark. A very slight degree of heat is sufficient to inflame it in the open air. Gentle pressure between the fingers, friction, or a temperature not much above its point of fusion kindles it readily. It burns rapidly even in the air, emitting a splendid white light, and causing intense heat. Its combustion is far more rapid iu oxygen gas, and the light far more vivid. The product of the perfect combustion of phosphorus is phosphorous pentoxid (P₂O₅), a white solid which readily takes up water, passing into phosphoric acid (which see, under phosphoric). Phosphorus may be made to combine with most of the metals, forming compounds called phosphides; when dissolved in fat oils it forms a solution which is luminous in the dark. It is chiefly used in the preparation of luciffer matches, and in the preparation of phosphoric acid. It is used to some extent in medicine in nervous affections, but is virulently poisonous except in very minute doses. Phosphorus presents a good example of allotropy, in that it can be exhibited in at least one other form, known as red or amorphous phosphorus, presenting completely different properties from common phosphorus. This variety is produced by keeping common phosphorus for a long time slightly below the boiling-point. It is a red, hard, brittle substance, not fusible, not poisonous, and not readily inflammable, so that it may be handled with impunity. When heated to the boiling-point it changes back to common phosphorus.
3. n. A small bottle containing 12 grains of phosphorus melted in half an ounce of olive-oil. On being uncorked in the dark this solution emits light enough to illuminate the dial of a watch, and it will retain this property for several years if not too frequently used.
4. n. [With a pl. phosphori (-rī).] In early use, a substance which emits light otherwise than as the result of ordinary combustion. Thus mention is made of the phosphori of Canton, Homberg, Baldwin, etc. The principal causes of such emission of light are previous exposure to light (insolation), to heat, to mechanical violence (friction, percussion, etc.), to electrical discharge, and to slow surface oxidation, as also the vital processes in the bodies of animals and plants.

Wiktionary

1. n. a chemical element (symbol P) with an atomic number of 15, that exists in several allotropic forms.
2. n. any substance exhibiting phosphorescence; a phosphor

GNU Webster's 1913

1. n. The morning star; Phosphor.
2. n. A poisonous nonmetallic element of the nitrogen group, obtained as a white, or yellowish, translucent waxy substance, having a characteristic disagreeable smell; this waxy allotropic form is also called yellow phosphorus, to distinguish it from another allotropic form, red phosphorus. It is very active chemically, must be preserved under water, and unites with oxygen even at ordinary temperatures, giving a faint glow, -- whence its name. It always occurs combined, usually in phosphates, as in the mineral apatite, in bones, etc. It is used in the composition on the tips of friction matches, and for many other purposes. The molecule contains four atoms. Symbol P. Atomic weight 31.0.
3. n. Hence, any substance which shines in the dark like phosphorus, as certain phosphorescent bodies.

WordNet 3.0

1. n. a planet (usually Venus) seen just before sunrise in the eastern sky
2. n. a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms