Reactive White Phosphorus

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  • Topic: Phosphorus, Match, Phossy jaw
  • Pages : 2 (352 words )
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  • Published : February 4, 2012
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Most people would use a lighter or a match to start a fire. Matches allow for a portable, easy-to-use source of fire. Many chemical reactions generate heat and fire, but matches are a fairly recent invention. Matches are also an invention you probably wouldn't choose to duplicate if civilization ended today or you were stranded on a desert island. The chemicals involved in modern matches are generally safe, but that wasn't always the case. The material of making a matches is red phosphorus.

A chemical equation of lighting a match is:

16KCl3 + 3P4 S3 --> 16 KCl + 9SO2

Actually phosphorus is found in three main forms: white, red, and black. (There are also numerous allotropes of each of these forms.)

White phosphorus is a soft, waxy, flammable substance, consisting of tetrahedral P4 molecules; it is often slightly yellowish because of the presence of impurities (hence, it is sometimes imaginatively known as yellow phosphorus). White phosphorus is highly reactive, and spontaneously ignites at about 30°C in moist air. It is usually stored under water, to prevent exposure to the air. It is also extremely toxic, even in very small quantities. It produces severe gastrointestinal irritation, diarrhea, and liver damage. It also causes burns when it comes in contact with skin. Chronic exposure to white phosphorus causes bony necrosis (especially of the jaw, a condition called "phossy-jaw") and anemia. White phosphorus should be handled with gloves! This procedure must be performed in a fume hood!

Black phosphorus is the least reactive form, and has little commercial value, but can be converted to white phosphorus by heating it under pressure.

Red phosphorus is stable at room temperature, but can be converted to the more reactive white phosphorus by heat, sunlight, or friction. Red phosphorus is used on the strike surface of the box that safety matches are stored in; the friction caused by dragging the match head across the rough surface converts some of...
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