Sulfur phosphide. Big encyclopedia of oil and gas

His experiments with human urine, he suggested that it contained gold particles due to its yellow color. He waited until the urine settled in barrels, then evaporated it, subjected the liquid to distillation. After, by combining this substance with sand and coal without air, he received a kind of white dust, which had the property of glowing in the dark. He started selling phosphorus to people, and then sold the secret formula of phosphorus to the chemist Kraft.

He glows!

Considering the chemical properties of phosphorus, one can understand why it glows in the absence of light. There are three types of phosphorus:
- White,
- the black,
- Red.

White phosphorus is colorless and very poisonous; it does not dissolve in water, but can dissolve in carbon disulfide. If white phosphorus is heated for a long time on low heat, it passes into the next form - red, which is not poisonous, and looks like a red-brown powder.

Chemistry and more

Phosphorus black differs from the previous two types in texture, color, and properties. It looks more like graphite and has a greasy texture. This type of white phosphorus is obtained only under enormous pressure at a temperature of about 200 degrees.

Phosphorus is analogous to nitrogen, but compared to the nitrogen atom, the phosphorus atom has a lower ionization energy.

Rather little time is required for white phosphorus to react with oxygen and oxidize. It is dangerous because of the ability to ignite spontaneously in air, which is why it should be stored in water. It is because of the oxidation reaction that a certain amount of energy is released, in other words, phosphorus begins to glow. Physicists in this case talk about the transition of chemical energy into light.

In nature, phosphorus occurs only in the form of compounds, the most important such compound is calcium phosphate - in nature, the mineral apatite. Varieties of apatite make up sedimentary rocks, the so-called phosphorites.

Phosphorus is a substance necessary for the life of plants, so it should be quite a lot contained in the soil. The richest deposits of phosphorites are in Siberia, Kazakhstan, Estonia, Belarus, they are also found in the United States, North Africa and Syria.

By the way...

White phosphorus actively used by the military. However, its destructive power is so great and dangerous, and human suffering is so great that a number of countries have decided to limit the use of this substance.

A couple of centuries ago, phosphorus terrified people who had the imprudence to pass by cemeteries in the dark. People said that they saw how the souls of the recently deceased leave the earth in the form of luminous balls. In fact, it was in the process of bone decay that the described substance was released. A light stream of light easily overcame a small layer of earth and broke free.

Phosphor paint is used to coat items that need to glow in the dark. Contrary to the name, it does not contain the chemical element phosphorus, and therefore is not poisonous. Modern paints of this type are usually non-radioactive.

Instruction

Purchase any small glowing plastic toy. It is best if it is made of polypropylene. Despite the fact that such toys are no longer made radioactive, just in case, check it with a dosimeter. Also make sure that after some time after the light goes out, the brightness of the light drops, and then it goes out completely until the toy is “charged” again. Do not confuse chemical luminous tubes with such toys: they are disposable and do not glow in them solid, but a liquid. It is impossible to use them for the manufacture of luminous paint.

Take any non-toxic solvent. It must have the property of dissolving polypropylene. Pour the granules in a jar with this solvent. Wait until they are completely dissolved in it. Do not use any sources of open flame near the solvent!

When dissolution is complete, pour paint in a bottle with a tight screw cap. Bottle and cap materials must also be solvent resistant.

When paint is needed, take a small saucer that is not used for cooking and is made of solvent resistant material. Pour some paint into it. Dip in paint brush or poster pen. Put an inscription on the object,

PHOSPHORUS, P, element of group V of the periodic system; atomic weight 31.03; Phosphorus isotopes have not been found. In compounds, phosphorus is trivalent and pentavalent. Its highest connection with hydrogen is PH 3; with oxygen, it gives the oxides P 2 O 3, P 2 O 4 and P 2 O 5. In terms of valence and type of compounds, phosphorus resembles nitrogen, but in properties (both phosphorus and its compounds) it is completely different from nitrogen. common in nature and found in almost all rocks in the form of inclusions of crystals of the mineral apatite. Phosphorus is found in the form of mineral accumulations of phosphorites and apatites. Apatites rarely occur in large masses, and the colossal deposits of this mineral in the Khibiny tundra in the USSR are an exception. Phosphorites are known in Georgia, Florida, North and South Carolina, Tennessee, Algeria, Tunisia, and on some islands of the Great Ocean. The USSR is extremely rich in phosphorites, the deposits of which are known in the Moscow region, in the Urals, in Kazakhstan, in Ukraine, in the Chuvash Republic, in Podolia, in the North Caucasus, etc. Minerals such as vivianite Fe 3 (PO 4) 2 8H 2 O and turquoise (Al 2 O 3) 2 P 2 O 5 5H 2 O, are aqueous salts phosphoric acid. Phosphorus is an indispensable component, part of the tissues of living organisms. Proteins containing phosphorus and lecithin are part of the muscles, nerves and brain. Bones contain phosphorus in the form of tricalcium salt of phosphoric acid.

Phosphorus can be obtained in several allotropic modifications. White phosphorus (ordinary, yellow) is a colorless, transparent vitreous substance or white small crystals; pure white phosphorus can only be obtained in the dark in the absence of oxygen and moisture. Fractional distillation or fractional crystallization results in completely pure phosphorus, which quickly turns yellow in the light. Such yellowing is explained by the formation of a thin film of red modification on the surface of phosphorus. With prolonged exposure to intense light on ordinary phosphorus, it can be completely converted to red. At 150°C in the absence of oxygen, ordinary phosphorus sublimates without changing color. Two modifications are known for white phosphorus - α and β; the first one crystallizes correct system(specific gravity 1.84), the second (ordinary phosphorus) - in hexagonal (specific gravity 1.88). The transition of α-phosphorus to β-phosphorus occurs under the following conditions:

Mohs hardness of phosphorus is 0.5. Its plasticity increases with increasing temperature. Molten phosphorus hardly wets the glass; surface tension 35.56 D/cm at 132.1°C and 43.09 D/cm at 78.3°C. The corresponding specific gravities of phosphorus are 1.665 and 1.714. The compressibility of ordinary phosphorus between 100 and 500 atm is 0.0000199 cm 2 /kg. The expansion coefficient of ordinary phosphorus from 0°C to 40° = 0.000125, and its volume at 44°C is 1.017 times the volume at 0°C. Heat capacity of white phosphorus (0-51°C) 0.183 cal/g; heat of fusion 5.03 cal/g. The weight of 1 liter of phosphorus vapor is 2.805 g (Williamson). Its molar weight in the range of temperatures from 313 ° C to red heat ranges from 128 to 119.8. Therefore, the structure of its molecule in this interval corresponds to P 4 . At high temperatures, it partially dissociates into P 2 . In solution, its molecule corresponds to the formula P 4; melting point of ordinary phosphorus 44.5°C; it slowly sublimates at 40°C, evaporates at normal temperature. Vapor pressure of ordinary solid phosphorus at 5°C - 0.03 mm, at 40°C - 0.50 mm. Solubility of phosphorus in water: 0.0003 g per 100 g of water at 15°C. Various solvents dissolve approximately phosphorus (in 100 hours of solvent): carbon disulfide 25, gasoline 1.5, almond oil 1.00, concentrated acetic acid 1.00, ether 0.45, ethanol(specific gravity 0.822) 0.25, glycerin 0.17 h. Hydrogen is well absorbed by phosphorus, especially during an electric discharge. Hydrogen is able to react with phosphorus in statu nascendi; the released gas no longer possesses this ability. Fluorine reacts at ordinary temperature with phosphorus without ignition, forming PF 3 with an excess of phosphorus and PF 5 with an excess of fluorine. Phosphorus combines vigorously with oxygen, forming, depending on the amount of reagents, phosphorous or phosphoric anhydride. Hydroquinone, sugar, glycerin, sodium arsenic acid slow down the oxidation reaction of phosphorus. Combining with atmospheric oxygen, phosphorus ignites, so it must be stored under water. The ignition temperature of phosphorus in air, in oxygen or in air diluted with an equal volume of carbon dioxide is 45.0-45.2°C. The ignition of ordinary phosphorus is promoted by rarefaction of the air and is prevented by compression. The presence of ozone and moisture in the atmosphere increases the ignition temperature. In an atmosphere of carbon disulfide, the ignition temperature of phosphorus is 87 ° C, turpentine - 18 °; phosphorus can be heated without ignition to 205°C if it is at rest; the slightest stirring causes ignition even at 45°C. Ordinary phosphorus ignites within 20 seconds when brought into contact with pure amalgamated aluminium. Nitrogen is absorbed by phosphorus, but does not react with it. White phosphorus glows in the dark when it comes into contact with atmospheric oxygen. The intensity of the glow depends on the concentration of oxygen. In pure oxygen below 27°C, phosphorus does not glow and does not oxidize. White phosphorus is poisonous and a dose of 0.15 g is lethal. In view of the ability of phosphorus to dissolve in fats, in case of poisoning, fatty foods and milk are completely unacceptable as they contribute to a better absorption of phosphorus into the body.

Red phosphorus is a modification that differs sharply in its physical and chemical properties from white phosphorus. Red phosphorus is formed from ordinary when an electric discharge is passed through the vapors of the latter. By heating a solution of white phosphorus in phosphorus tribromide at a temperature of 170-190 ° C, one can isolate the so-called. raspberry variety phosphorus. This variety has a colloidal structure and is transitional between ordinary and red phosphorus; the presence of phosphorus triiodide accelerates (3 times) the reaction. By heating ordinary phosphorus with sulfur or sulfide, and then processing the resulting mixture aqueous solution alkali or ammonia, you can also get red phosphorus. Red phosphorus in technology is obtained by heating ordinary phosphorus without air at a temperature of 240-250 ° C; The reaction is accompanied by the release of heat. The color of red phosphorus changes depending on the temperature of the preparation. At low temperatures it has a crimson hue, at high - violet or purple. Selenium accelerates the transition of white phosphorus to red. The separation of the admixture of ordinary phosphorus from red is carried out by treatment with carbon disulfide for 50 hours at 250-260 ° C or 10% sodium alkali solution for 2 hours; it is also possible to wash phosphorus with a mixture of carbon disulfide and calcium chloride solution with a specific gravity of 1.349-1.384. In this case, ordinary phosphorus dissolves in carbon disulfide, and red settles into a solution of calcium chloride. There is an assumption that the white and red modifications of phosphorus are chemically different; the proof of this position is that when molten yellow and red phosphorus are mixed, no transition of the first into the second is observed. When heated within the range of 280-400 ° C, red phosphorus vapor partially thickens into the so-called. metallic phosphorus. With the rapid cooling of vapors, partially red phosphorus is formed, and the greater the amount, the higher the temperature was before solidification. The surface of the receiver acts catalytically on the formation of red phosphorus. The duration of heating does not affect the process, but cooling should occur quickly. There is an opinion (A. Stock) that red phosphorus is formed as a result of the combination of dissociated phosphorus molecules with each other or with non-dissociated molecules and that the formation of P 4 yellow phosphorus molecules is relatively slower than the formation of red phosphorus molecules. The condensation of red phosphorus from the vapor state is independent of the presence of liquid yellow phosphorus. Red phosphorus, obtained by cooling vapors that had a temperature of 1200 ° C, and at a pressure of 5 mm, contains no more than 1% yellow phosphorus; hence it follows that the P 2 and P 4 molecules take part in the formation of red phosphorus. It is possible that this formation follows the equation mР 2 + nP 4 = P 2 m+4 n. There are suggestions that the molten phosphorus contains P 4 molecules of yellow phosphorus and P n molecules of red phosphorus in equilibrium:

Above the melting point of red phosphorus (592.5°C, according to other sources 589.5°C), most of the molecules are in the form of P 4, so that a white variety forms on rapid cooling, but slow cooling allows the equilibrium to shift to the right, and red phosphorus is released during solidification. The specific gravity of red phosphorus ranges from 2.05 to 2.3, which makes us consider it as a mixture of two modifications. There is an assumption that red phosphorus is monoclinic in its crystal structure. The compressibility of red phosphorus (between 100-500 atm) is 0.0000092 cm 2 /kg; The melting point of red phosphorus depends on the heating rate and varies within ±0.5°C. Vapor pressure of red phosphorus at 230°C - 0 mm, at 360°C - 0.1 mm, at 500°C - 9 atm. Red phosphorus is insoluble in carbon disulfide. Red phosphorus obtained with the release of heat contains less energy and is much less active than white phosphorus. Red phosphorus is not poisonous, it does not ignite in air, which is why its storage is not so dangerous. Red phosphorus ignites on impact. Gittorf claims that the transition of red phosphorus to yellow is not observed at a temperature of 320 ° C, but the latter is formed at 358 ° C. In a sealed tube, red phosphorus is strong at temperatures from 450 to 610°C.

Crystalline, or violet, phosphorus has a crystalline structure, the crystals are trigonal with an axial ratio a:c = 1:1.1308. It is obtained by crystallization from molten lead or bismuth, as well as by heating white phosphorus under a pressure of 500 kg / cm 2 in the presence of sodium. Insoluble in carbon disulfide; specific gravity of violet phosphorus 2.34; it sublimates at 690.9°C; melting point 589.5°C at a pressure of 43.1 atm.

Black phosphorus (R. Bridgeman) is obtained from ordinary phosphorus when heated to 216 ° C under a pressure of 89 atm. It is insoluble in carbon disulfide; ignites at a temperature of 400 ° C and does not ignite on impact; the transition temperature of red phosphorus to black 575°C; red phosphorus turns into black when heated in a hydrogen atmosphere at 200°C and a pressure of 90 atm (V. Ipatiev). Only 2 modifications are of technical importance: white (yellow) and red phosphorus.

Getting phosphorus. White phosphorus is usually prepared, which, if necessary, is subsequently converted into a red modification. The starting material for obtaining phosphorus is phosphorites - natural tricalcium phosphate, best of all bone ash. The process consists in the reduction of phosphate with carbon or the action of aluminum on sodium metaphosphate mixed with silica:

6NaPO 3 + 3SiO 2 + 10Al \u003d 3Na 2 SiO 3 + 5Al 2 O 3 + 6P.

There are 2 methods of factory production of phosphorus: 1) the old Pelletier method, which consists in treating phosphate (bone meal) with dilute sulfuric acid, and tricalcium phosphate is converted into monocalcium phosphate:

Ca 3 (PО 4) 2 + 2H 2 SO 4 \u003d 2CaSO 4 + Ca (H 2 PО 4) 2.

The solution of the latter is separated from gypsum (CaSO 2H 2 O), evaporated, calcined with coal and calcium metaphosphate is obtained:

Ca (H 2 RO 4) 2 \u003d 2H 2 O + Ca (RO 3) 2,

which after strong calcination gives phosphorus, tricalcium phosphate and carbon monoxide:

ZCa (RO 3) 2 + 10C \u003d Ca 3 (RO 4) 2 + 4P + 10CO.

According to the Wehler method, they proceed directly from tricalcium phosphate:

2Ca 3 (PO 4) 2 + 6SiO 2 + 10C \u003d 6CaSiO 3 + 10CO + 4P.

This process requires a high temperature and began to be used only with the introduction of electric furnaces. There is also a method for obtaining phosphorus from free phosphoric acid mixed with coal using electric current. Academician in the USSR. E. V. Britske developed a method for obtaining phosphorus in blast furnaces.

Commercial product always contains traces of arsenic, silicon compounds and carbon. Mechanical impurities are removed by filtration, and even better by re-distillation. The transformation of white phosphorus into red is carried out at a temperature of 260°C; a decrease in pressure slows down the course of the reaction; lighting speeds up the process; catalysts (iodine, selenium) also affect.

Analytical determination of phosphorus. Phosphorus vapor acts on wet paper impregnated with silver nitrate, causing it to blacken. The blackness is due to the formation of phosphorous and metallic silver . The reaction proceeds in 2 stages. Phosphorus reacts with water to form hydrogen phosphorous and hypophosphorous acid:

P 4 + 6H 2 O \u003d ZN 3 RO 2 + PH 3.

The compounds resulting from the reaction act on silver nitrate:

H3PO 2 +2H 2 O + 4AgNO 3 \u003d 4HNO 3 +H3PO 4 +4Ag;

PH 3 + 3AgNO 3 \u003d 3HNO 3 + PAg 3.

This reaction is applicable for the discovery of white phosphorus only in the absence of H 2 S, AsH 3 , SbH 3 , as well as formic aldehyde and formic acid. Opening poisonous phosphorus(according to Mitcherlich) is based on the ability of phosphorus to glow in humid air in the dark. The crushed substance, in which phosphorus is supposed to be discovered, is placed in a flask connected to a refrigerator. So much water is poured into the flask to obtain a liquid slurry, and the contents of the flask are neutralized with tartaric acid until slightly acidic. When the flask is heated in the dark, an insignificant amount of phosphorus (a few mg) already causes a glow in the refrigerator. Since the phenomenon of luminescence can also be due to the presence of phosphorus sulfide after its decomposition when heated, it is recommended that the flask be heated not directly, but by passing water vapor into it. The glow of phosphorus is not observed in the presence of traces of ammonia, carbon disulfide, alcohol vapors, essential oils and unsaturated hydrocarbons, so the distillation should not be stopped too early. If, nevertheless, no glow is observed, then the filtrate is oxidized with chlorine water, evaporating in a water bath to a small volume, and a test is made for phosphoric acid. The glow of phosphorus can also be observed in the flask, heating the liquid first to a boil, then cooling it slightly and heating it again to a boil; 0.0171 mg of phosphorus glow very clearly, 0.0085 mg - clearly, 0.0042 mg - weakly and 0.001 mg - doubtful. Phosphorus, being reduced by hydrogen in statu nascendi, gives hydrogen phosphorous, which, mixed with hydrogen, burns with an emerald green flame at the outlet of a platinum-tipped tube when ignited. organic matter prevent the appearance of color, and therefore d. b. separated. Nitric acid easily oxidizes phosphorus to phosphoric acid:

ZR 4 +20NNO 3 +8H 2 O \u003d 12H 3 RO 4 +20NO3.

Phosphorus is quantified after oxidation to phosphoric acid and precipitation as MgNH 4 PO 4 .

Application . Phosphorus is one of the elements without which the proper development of plant and animal organisms is impossible. There is a direct relationship between the content of phosphorus in the nutrient medium and plant growth. Phosphorus, along with nitrogen and potassium, is the most important nutrient, which is needed by page - x. plants. Being alienated from the field along with the grain harvest, phosphorus does not have a closed cycle in its cycle, and therefore, without its artificial introduction into the soil from the outside, soil depletion is observed. Fertilizers containing phosphorus make up the largest group. Phosphorus is used in military affairs as a smoke-generating agent and for filling incendiary projectiles.

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Red phosphorus has a specific gravity of 220; melts at a pressure of 43 atm at a temperature of 590 C.

Red phosphorus reacts vigorously with alkali metals in liquid ammonia to form alkali metal phosphides of varying degrees of polymerization, depending on the ratio of phosphorus and alkali metal taken into the reaction. The subsequent addition of alkyl halides to the reaction mixture leads to the formation of the corresponding phosphines or polyphosphines, and with the additional action of group VI elements on the same reaction mixture, derivatives of pentavalent phosphorus are formed.

Red phosphorus is obtained by heating white at 280 - 340 without air. It is a powder. Red phosphorus, unlike white phosphorus, is not poisonous.

Red phosphorus is obtained by heating white phosphorus for a long time at 280 - 340 C without air. It is a dark crimson powder, insoluble in water and carbon disulfide. Red phosphorus is chemically less active than white phosphorus. It ignites only at a temperature of about 260 C.

Red phosphorus is obtained by heating white phosphorus without access to oxygen at 280 - 340 C. In air, it ignites at 240 C, is insoluble in carbon disulfide, and is less reactive than white phosphorus.

Red phosphorus is different from white phosphorus in many ways. It is less toxic than white phosphorus, oxidizes very slowly in air, does not glow in the dark, and does not dissolve in carbon disulfide. With strong heating, red phosphorus sublimates, and its vapors, when thickened, give white phosphorus.

Red phosphorus is capable of the same chemical reactions as white phosphorus, but reactions with red phosphorus proceed much more slowly than with white phosphorus.

Red phosphorus has different properties than white phosphorus and its chemical activity is much less, so it does not spontaneously ignite in air. Red phosphorus does not dissolve in carbon disulfide and ether.

Red phosphorus is obtained from white by prolonged heating without air at 280 - 300 C. Its crystal lattice is atomic, it does not dissolve in organic solvents, it is not poisonous. Store it in a tightly sealed container.

Red phosphorus practically does not oxidize in air and ignites only at temperatures above 250 C.

Plan:

Introduction

• 1. History
• 2 origin of name
• 3 Getting
• 4 Physical properties
  • 4.1 White phosphorus
  • 4.2 Yellow phosphorus
  • 4.3 Red phosphorus
  • 4.4 Black phosphorus
  • 4.5 metallic phosphorus
• 5 Chemical properties
  • 5.1 Interaction with simple substances
  • 5.2 Interaction with water
  • 5.3 Interaction with alkalis
  • 5.4 Restorative properties
• 6 Application
  • 6.1 Elemental phosphorus
  • 6.2 Phosphorus compounds in agriculture
  • 6.3 Phosphorus compounds in industry
  • 6.4 Phosphate binders
• 7 The biological role of phosphorus compounds
  • 7.1 Toxicology of elemental phosphorus
  • 7.2 Toxicology of phosphorus compounds
Notes

Introduction

Phosphorus(from Greek phosphoros - luminiferous; lat. Phosphorus) - one of the most common elements of the earth's crust, its content is 0.08-0.09% of its mass. Concentration in sea water 0.07 mg/l. It is not found in the free state due to its high chemical activity. It forms about 190 minerals, the most important of which are apatite Ca 5 (PO 4) 3 (F,Cl,OH), phosphorite Ca 3 (PO 4) 2 and others. Phosphorus is found in all parts of green plants, and even more in fruits and seeds (see phospholipids). Contained in animal tissues, is part of proteins and other essential organic compounds (ATP, DNA), is an element of life.

1. History

Phosphorus discovered by the Hamburg alchemist Hennig Brand in 1669. Like other alchemists, Brand tried to find the philosopher's stone, but received a luminous substance. Brand focused on experiments with human urine, because he believed that it, having a golden color, may contain gold or something necessary for mining. Initially, his method consisted in the fact that at first the urine was settled for several days until the unpleasant odor disappeared, and then boiled to a sticky state. By heating this paste to high temperatures and bringing it up to the appearance of bubbles, he hoped that, when condensed, they would contain gold. After several hours of intense boiling, grains of a white wax-like substance were obtained, which burned very brightly and, moreover, flickered in the dark. Brand named this substance phosphorus mirabilis(lat. "miraculous carrier of light"). Brand's discovery of phosphorus was the first discovery of a new element since antiquity.

Somewhat later, phosphorus was obtained by another German chemist, Johann Kunkel.

Regardless of Brand and Kunkel, phosphorus was obtained by R. Boyle, who described it in the article "Method of preparing phosphorus from human urine", dated October 14, 1680 and published in 1693.

An improved method for obtaining phosphorus was published in 1743 by Andreas Marggraf.

There is evidence that Arab alchemists were able to obtain phosphorus in the 12th century.

The fact that phosphorus is a simple substance was proved by Lavoisier.

2. Origin of the name

In 1669, Henning Brand, by heating a mixture of white sand and evaporated urine, obtained a substance glowing in the dark, first called "cold fire". The secondary name "phosphorus" comes from the Greek words "φῶς" - light and "φέρω" - I carry. In ancient Greek mythology, the name Phosphorus (or Eosphorus, other Greek. Φωσφόρος ) was worn by the Guardian of the Morning Star.

3. Receipt

Phosphorus is obtained from apatites or phosphorites as a result of interaction with coke and silica at a temperature of 1600 ° C:

• 2Ca 3 (PO 4) 2 + 10C + 6SiO 2 → P 4 + 10CO + 6CaSiO 3 .

The resulting white phosphorus vapor condenses in the receiver under water. Instead of phosphorites, other compounds can be reduced, for example, metaphosphoric acid:

• 4HPO 3 + 12C → 4P + 2H 2 + 12CO.

4. Physical properties

Elemental phosphorus under normal conditions represents several stable allotropic modifications; The problem of phosphorus allotropy is complex and not fully resolved. Usually, four modifications of a simple substance are distinguished - white, red, black and metallic phosphorus. Sometimes they are also called the main allotropic modifications, implying that all the others are a variety of these four. Under normal conditions, there are only three allotropic modifications of phosphorus, and under conditions of ultrahigh pressures, there is also a metallic form. All modifications differ in color, density and other physical characteristics; there is a noticeable tendency to a sharp decrease in chemical activity during the transition from white to metallic phosphorus and an increase in metallic properties.

Allotropic modifications of phosphorus

4.1. White phosphorus

White phosphorus is a white substance (may have a yellowish tint due to impurities) with a melting point of 44.1 °C. By appearance it is very similar to refined wax or paraffin, easily cut with a knife and deformed with little effort.

Hennig Brand's discovery of phosphorus
Joseph Wright, 1771

White phosphorus has a molecular structure; formula P 4 . Cast in an inert atmosphere in the form of sticks (ingots), it is stored in the absence of air under a layer of purified water or in special inert media.

Easily soluble in organic solvents. The solubility of white phosphorus in carbon disulfide is used for its industrial purification from impurities. The density of white phosphorus is the lowest among all its modifications and is about 1823 kg/m³. White phosphorus melts at 44.1 °C. In the vapor state, the dissociation of phosphorus molecules occurs.

Chemically, white phosphorus is extremely active. For example, it is slowly oxidized by air oxygen already at room temperature and glows (pale green glow). The phenomenon of this kind of glow due to chemical oxidation reactions is called chemiluminescence (sometimes erroneously phosphorescence).

White phosphorus is not only chemically active, but also very poisonous (causes damage to bones, bone marrow, necrosis of the jaws). The lethal dose of white phosphorus for an adult male is 0.05-0.1 g.

4.2. yellow phosphorus

Unrefined white phosphorus is commonly referred to as "yellow phosphorus". Highly toxic (MPC in ambient air 0.0005 mg/m³), flammable crystalline substance from light yellow to dark brown. Specific gravity 1.83 g/cm³, melts at +34 °C, boils at +280 °C. It does not dissolve in water, easily oxidizes in air and ignites spontaneously. It burns with a dazzling bright green flame with the release of thick white smoke - small particles of tetraphosphorus decaoxide P 4 O 10 . Despite the fact that as a result of the reaction between phosphorus and water (4P + 6H 2 O → PH 3 + 3H 3 RO 2) poisonous phosphine gas (PH 3) is released, large amounts of water are used to extinguish phosphorus (to reduce the temperature of the ignition source and transfer of phosphorus to a solid state) or a solution of copper sulfate (copper sulfate), after quenching, phosphorus is covered with wet sand. To protect against spontaneous combustion, yellow phosphorus is stored and transported under a layer of water (calcium chloride solution).

4.3. red phosphorus

red phosphorus

Red phosphorus, also called violet phosphorus, is a more thermodynamically stable modification of elemental phosphorus. It was first obtained in 1847 in Sweden by the Austrian chemist A. Schrötter by heating white phosphorus at 500 ° C in an atmosphere of carbon monoxide (CO) in a sealed glass ampoule.

Red phosphorus has the formula P n and is a polymer with a complex structure. Depending on the method of production and the degree of crushing of red phosphorus, it has shades from purple-red to violet, and in the cast state it has a dark purple metallic luster with a copper tint. The chemical activity of red phosphorus is much lower than that of white; it has exceptionally low solubility. It is possible to dissolve red phosphorus only in certain molten metals (lead and bismuth), which is sometimes used to obtain large crystals of it. So, for example, the German physical chemist I. V. Gittorf in 1865 for the first time received perfectly built, but small crystals (Gittorf's phosphorus). Red Phosphorus does not ignite spontaneously in air, up to a temperature of 240–250 °C (when it changes to a white form during sublimation), but ignites spontaneously upon friction or impact; it completely lacks the phenomenon of chemiluminescence. Insoluble in water, as well as in benzene, carbon disulfide and others, soluble in phosphorus tribromide. At the sublimation temperature, red phosphorus is converted into vapor, upon cooling of which mainly white phosphorus is formed.

Its poisonousness is thousands of times less than that of white, so it is used much more widely, for example, in the production of matches (the grating surface of boxes is coated with a composition based on red phosphorus). The density of red phosphorus is also higher, reaching 2400 kg/m³ when cast. When stored in air, red phosphorus in the presence of moisture gradually oxidizes, forming a hygroscopic oxide, absorbs water and becomes damp (“soaked”), forming viscous phosphoric acid; Therefore, it is stored in an airtight container. When "soaked" - washed with water from the remnants of phosphoric acids, dried and used for its intended purpose.

4.4. black phosphorus

Black phosphorus is the most thermodynamically and chemically least stable active form elemental phosphorus. For the first time, black phosphorus was obtained in 1914 by the American physicist P. W. Bridgman from white phosphorus in the form of black shiny crystals with a high (2690 kg / m³) density. To carry out the synthesis of black phosphorus, Bridgman applied a pressure of 2 × 10 9 Pa (20 thousand atmospheres) and a temperature of about 200 ° C. The beginning of the fast transition lies in the region of 13,000 atmospheres and a temperature of about 230 °C.

Black phosphorus is a black substance with a metallic luster, greasy to the touch and very similar to graphite, and with no solubility in water or organic solvents. It is possible to set fire to black phosphorus only by first heating it strongly in an atmosphere of pure oxygen up to 400 ° C. Black phosphorus conducts electricity and has the properties of a semiconductor. The melting point of black phosphorus is 1000 ° C under a pressure of 18 × 10 5 Pa.

4.5. metallic phosphorus

At 8.3 × 10 10 Pa, black phosphorus passes into a new, even denser and inert metal phase with a density of 3.56 g / cm³, and with a further increase in pressure to 1.25 × 10 11 Pa, it becomes even more compacted and acquires a cubic crystal lattice, while its density increases to 3.83 g/cm³. Metallic phosphorus conducts electricity very well.

5. Chemical properties

The chemical activity of phosphorus is much higher than that of nitrogen. The chemical properties of phosphorus are largely determined by its allotropic modification. White phosphorus is very active; in the process of transition to red and black phosphorus, the chemical activity decreases sharply. White phosphorus glows in the dark in air, the glow is due to the oxidation of phosphorus vapor to lower oxides.

In the liquid and dissolved state, as well as in vapors up to 800 ° C, phosphorus consists of P 4 molecules. When heated above 800 ° C, the molecules dissociate: P 4 \u003d 2P 2. At temperatures above 2000 °C, molecules break up into atoms.

5.1. Interaction with simple substances

Phosphorus is easily oxidized by oxygen:

• 4P + 5O 2 → 2P 2 O 5 (with excess oxygen),
• 4P + 3O 2 → 2P 2 O 3 (with slow oxidation or with a lack of oxygen).

Interacts with many simple substances - halogens, sulfur, some metals, showing oxidizing and reducing properties:

with metals - an oxidizing agent, forms phosphides:

• 2P + 3Ca → Ca 3 P 2 ,
• 2P + 3Mg → Mg 3 P 2 .

phosphides are decomposed by water and acids to form phosphine

with non-metals - reducing agent:

• 2P + 3S → P 2 S 3 ,
• 2P + 3Cl 2 → 2PCl 3 .

Does not interact with hydrogen.

5.2. Interaction with water

Interacts with water, while disproportionation:

• 8P + 12H 2 O \u003d 5PH 3 + 3H 3 PO 4 (phosphoric acid).

5.3. Interaction with alkalis

In alkali solutions, disproportionation occurs to a greater extent:

• 4P + 3KOH + 3H 2 O → PH 3 + 3KH 2 RO 2.

5.4. Restorative properties

Strong oxidizing agents convert phosphorus to phosphoric acid:

• 3P + 5HNO 3 + 2H 2 O → 3H 3 PO 4 + 5NO;

• 2P + 5H 2 SO 4 → 2H 3 PO 4 + 5SO 2 + 2H 2 O.

The oxidation reaction also occurs when matches are ignited; Berthollet salt acts as an oxidizing agent:

• 6P + 5KClO 3 → 5KCl + 3P 2 O 5

6. Application

Phosphorus is the most important biogenic element and at the same time is very widely used in industry. Red phosphorus is used in the manufacture of matches. It, together with finely ground glass and glue, is applied to the side surface of the box. When a match head is rubbed, which includes potassium chlorate and sulfur, ignition occurs.

6.1. Elemental phosphorus

Perhaps the first property of phosphorus, which man put to his service, is flammability. The combustibility of phosphorus is very high and depends on the allotropic modification.

White ("yellow") phosphorus is the most chemically active, toxic and flammable, and therefore it is very often used (in incendiary bombs, etc.).

Red phosphorus is the main modification produced and consumed by industry. It is used in the manufacture of matches, explosives, incendiary compositions, various types fuel, as well as extreme pressure lubricants, as a getter in the production of incandescent lamps.

6.2. Phosphorus compounds in agriculture

Phosphorus (in the form of phosphates) is one of the three most important biogenic elements (NPK), involved in the synthesis of ATP. Most of the phosphoric acid produced is used to obtain phosphate fertilizers - superphosphate, precipitate, ammophoska, etc.

6.3. Phosphorus compounds in industry

Phosphates are widely used:

• as complexing agents (water softeners),
• in the composition of metal surface passivators (corrosion protection, for example, the so-called “mazhef” composition).

6.4. Phosphate binders

The ability of phosphates to form a strong three-dimensional polymer network is used to make phosphate and aluminophosphate binders.

7. Biological role of phosphorus compounds

Phosphorus is present in living cells in the form of ortho- and pyrophosphoric acids, is part of nucleotides, nucleic acids, phosphoproteins, phospholipids, coenzymes, enzymes. Human bones are composed of hydroxyapatite 3Ca 3 (PO 4) 3 Ca(OH) 2 . The composition of tooth enamel includes fluorapatite. The main role in the transformation of phosphorus compounds in humans and animals is played by the liver. Exchange phosphorus compounds regulated by hormones and vitamin D. The daily human need for phosphorus is 800-1500 mg. With a lack of phosphorus in the body, various bone diseases develop.

7.1. Toxicology of elemental phosphorus

• red phosphorus practically non-toxic. Dust of red phosphorus, getting into the lungs, causes pneumonia with chronic action.
• White phosphorus very toxic, soluble in lipids. Lethal dose white phosphorus - 50-150 mg. Getting on the skin, white phosphorus causes severe burns.

Acute phosphorus poisoning is manifested by burning in the mouth and stomach, headache, weakness, and vomiting. After 2-3 days, jaundice develops. Chronic forms are characterized by a violation of calcium metabolism, damage to the cardiovascular and nervous systems. First aid for acute poisoning - gastric lavage, laxatives, cleansing enemas, intravenous glucose solutions. In case of skin burns, treat the affected areas with solutions of copper sulfate or soda. MPC of phosphorus vapors in the air of industrial premises is 0.03 mg/m³, temporarily permissible concentration in the atmospheric air is 0.0005 mg/m³, MPC in drinking water is 0.0001 mg/dm³.

7.2. Toxicology of phosphorus compounds

Some phosphorus compounds (phosphine) are highly toxic. Chemical warfare agents sarin, soman, tabun, V-gases are phosphorus compounds.

Notes

1. Phosphorus: electronegativity - www.webelements.com/phosphorus/electronegativity.html . WebElements.
2. Sulfur and Phosphorus Compounds - www.cem.msu.edu/~reusch/VirtualText/special2.htm.
3. Editorial staff: Zefirov N. S. (editor-in-chief) Chemical Encyclopedia: in 5 volumes. - Moscow: Great Russian Encyclopedia, 1999. - V. 5. - S. 145.
4. J.P. Riley and Skirrow G. Chemical Oceanography V. 1, 1965
5. W. Schroeter, K.-H. Lautenschläger, H. Bibrak and others. Chemistry = Chemie. - M .: Chemistry, 1989. - S. 351. - ISBN 5-7245-0360-3
6. UNIAN - health - What happens to phosphorus? - health.unian.net/rus/detail/185459

This abstract is based on an article from the Russian Wikipedia. Synchronization completed on 07/09/11 21:43:39
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