Chemical element phosphorus belongs to the V group of a periodic system. More than ten of its modifications, the most important of them — white, black and red phosphorus are known. They have razliny physical properties, also methods of their receiving differ.
Instruction
1. In earth crust the average content of phosphorus is 0.105% on weight, in water of the seas and oceans — 0.07 mg/l. There are about 200 phosphoric minerals, all of them are phosphates. The most important of them — apatite, a basis of phosphorites. Crystal black phosphorus is thermally steady, red and white phosphorus meta are stable. However because of the small speed of transformation they are capable to remain in normal conditions unlimited time.
2. White phosphorus represents a transparent crystal or waxy weight which when cooling becomes fragile. Because of the big index of refraction of light and high dispersion the crystals of white phosphorus are similar to diamonds. They are received by means of condensation of vapors and hardening of fusion at a temperature of 76.9 °C.
3. If couples are condensed at a temperature of 190 °C, brown phosphorus is formed, this modification is unstable. It turns into mix of red and white phosphorus when temperature becomes above 100 °C.
4. When heating over 180 °C without access of air begin to collapse the system of communications therefore there is a polymerization which leads to formation of red phosphorus. A number of its versions is known, they differ on density, temperature of melting and color which varies from orange to black-violet.
5. If pressure exceeds 1.2 Gpa, white phosphorus turns into crystal black. For transition to it red phosphorus needs more high pressure — 2.5 Gpa. Transition is facilitated by heating to 200 °C.
6. Black phosphorus reminds graphite, the structure represents it the corrugated layers which are poorly connected among themselves. It can be received with an atmospheric pressure if to heat red phosphorus a long time together with mercury at a temperature of 300 °C in the presence of a priming.
7. White phosphorus is extremely active, however upon transition to red and black phosphorus its chemical activity sharply decreases. On air white phosphorus glows in the dark. Its name phosphoros is connected with this property - in translation from Greek means lightful.
8. Phosphorus is used for production of various fertilizers and phosphates which are applied as mineral fertilizing, including in livestock production. White phosphorus is smoke-generating and incendiary means for tracer ammunition. Red it is used in the match industry and also as a thermoplastic component in production of glow lamps.