White phosphorus at the lowest heat. Converting white phosphorus to red

Crystalline sulfur Sulfur dioxide (in crystals)

Sulfur

Sulfur S is a hard, brittle, yellow crystalline substance with a melting point of 119.3°C. But do not confuse this sulfur with the sulfur found in matches. The heads of matches mainly contain complex substances, one of which is potassium chlorate (KClO3), which can spontaneously ignite with friction or temperature. Sulfur- a simple substance and is present here as one of the components that make up the match head.

Sulfur modifications:

There are two modifications of sulfur: brittle sulfur And plastic sulfur. At 113 °C crystalline sulfur melts into a yellow, watery liquid. Molten sulfur at a temperature of 187°C becomes very viscous and quickly darkens. At the same time, its structural state changes. And if you heat sulfur to 445 °C, it boils. By pouring boiling sulfur in a thin stream into cold water, you can obtain plastic sulfur - a rubber-like modification consisting of polymer chains. In this state, sulfur is able to deform and stretch without collapsing. But as soon as it lies in the air for several days, it turns back into a fragile material.

Sulfur is a dielectric. It can serve as a heat insulator.

Sulfur easily oxidizes almost all metals except gold Au, platinum Pt and ruthenium Ru. Sulfur oxidizes alkaline (sodium Na, potassium K, lithium Li, calcium Ca) and alkaline earth metals (aluminum Al, magnesium Mg) even at room temperature. In the air crystalline sulfur burns with a blue flame to form sulfur dioxide SO 2 (a gas with an unpleasant suffocating odor). When sulfur is burned in hydrogen, a poisonous gas is formed - hydrogen sulfide.

Many products, when spoiled, emit a specific smell of hydrogen sulfide. Sulfur is used industrially to produce sulfuric acid. Oxidizing sulfur dioxide SO 2 in an oxygen-enriched environment is obtained sulfur trioxide SO 3 is a viscous transparent liquid.

Sulfuric anhydride or sulfur trioxide SO 3 at room temperature is a colorless, easily volatile liquid (t boiling point = 45 ° C), which over time turns into an asbestos-like modification consisting of shiny silky crystals. Sulfuric anhydride fibers are stable only in a sealed container. Absorbing moisture from the air, they turn into a thick, colorless liquid - oleum (from the Latin oleum - “oil”). Although formally oleum can be considered as a solution of SO 3 in H 2 SO 4.

Sulfur dioxide exhibits a strong bleaching effect: if, for example, a red rose is placed in a container with sulfur dioxide SO 2, it will lose its color.

Phosphorus

This substance can exist in two forms: red phosphorus And white phosphorus(white phosphorus is also called yellow phosphorus).

White phosphorus (or yellow phosphorus) is a poisonous, highly reactive, soft, waxy substance of pale yellow color, soluble in carbon disulfide and benzene. In air, white phosphorus ignites at 34 °C and burns with a bright white flame to form phosphorus oxide. White phosphorus melts at a temperature of 44.1°C and glows in the dark. May cause severe burns in case of contact with skin.

Very poisonous: a lethal dose of about 0.1 g (about the same as potassium cyanide - 0.12 g). Due to the danger of spontaneous combustion in air, white phosphorus is stored under a layer of water. and black phosphorus are less toxic, since they are non-volatile and practically insoluble in water. White phosphorus is already at room temperature, and other modifications of phosphorus, when heated, react with many simple substances: halogens (fluorine, chlorine, bromine, iodine, astatine), oxygen, sulfur, and some metals. If you heat white phosphorus to 300 0 C without access to air, it gradually turns into red phosphorus. Red phosphorus is a solid, non-toxic, does not glow in the dark and does not spontaneously ignite.

The name red phosphorus refers to several modifications that differ in density and color: it ranges from orange to dark red and even purple. All varieties red phosphorus insoluble in organic solvents, compared to white phosphorus they are less reactive (red phosphorus ignites in air at t>200 °C)

Water does not dissolve phosphorus. It is usually dissolved in ethyl alcohol.

Under pressure of hundreds of atmospheres, black phosphorus is obtained, whose properties are similar to metal (it conducts electricity and shines). Black phosphorus has a crystal lattice similar to metals.

Why does phosphorus glow?

If they say that phosphorus glows, then they only mean white phosphorus! In its molecule (the vertices of a pyramid with a triangle base), each vertex has a pair of electrons that are located outside the surface of the imaginary pyramid. Phosphorus atoms are “open” and are easily accessible to any atoms of other elements - oxidizing agents (for example, oxygen from the air). The available electron pairs of phosphorus serve as a “bait” for any other atoms that are ready to attach someone else’s electron (having high electronegativity). White phosphorus glows for a reason - it oxidizes - first, oxygen atoms are located between phosphorus atoms. This happens until all free electron pairs are attached to oxygen. After this, white phosphorus stops glowing and turns into phosphorus oxide P2O5.

Phosphorus oxide is a relatively stable substance, but it actively reacts with water, forming metaphosphoric acid HPO 3 and orthophosphoric acid H 3 PO 4

Phosphorus acids

When phosphorus oxide P2O5 is dissolved in water, it forms phosphoric acid H3PO4. This acid is one of the weak acids, therefore it does not react with most metals, but only removes the oxide film on their surface. It is often used when repairing electrical equipment, soldering electronic boards, etc. It is a good rust remover.

Phosphorus forms two acids: one is orthophosphoric acid, the second is metaphosphoric(HPO 3). But the second acid is not a stable compound and quickly oxidizes, forming orthophosphoric acid.

Designation - P (Phosphorus);
Period - III;
Group - 15 (Va);
Atomic mass - 30.973761;
Atomic number - 15;
Atomic radius = 128 pm;
Covalent radius = 106 pm;
Electron distribution - 1s 2 2s 2 2p 6 3s 2 3p 3 ;
melting temperature = 44.14°C;
boiling point = 280°C;
Electronegativity (according to Pauling/according to Alpred and Rochow) = 2.19/2.06;
Oxidation state: +5, +3, +1, 0, -1, -3;
Density (no.) = 1.82 g/cm 3 (white phosphorus);
Molar volume = 17.0 cm 3 /mol.

Phosphorus compounds:

Phosphorus (the carrier of light) was first obtained by the Arab alchemist Ahad Behil in the 12th century. Of the European scientists, the first to discover phosphorus was the German Hennig Brant in 1669, while conducting experiments with human urine in an attempt to extract gold from it (the scientist believed that the golden color of urine was caused by the presence of gold particles). Somewhat later, phosphorus was obtained by I. Kunkel and R. Boyle - the latter described it in his article “Method of preparing phosphorus from human urine” (October 14, 1680; the work was published in 1693). Lavoisier later proved that phosphorus is a simple substance.

The phosphorus content in the earth's crust is 0.08% by mass - this is one of the most common chemical elements on our planet. Due to its high activity, phosphorus in a free state does not occur in nature, but is part of almost 200 minerals, the most common of which are apatite Ca 5 (PO 4) 3 (OH) and phosphorite Ca 3 (PO 4) 2.

Phosphorus plays an important role in the life of animals, plants and humans - it is part of such biological compounds as phospholipids, and is also present in proteins and other important organic compounds such as DNA and ATP.

Rice. The structure of the phosphorus atom.

The phosphorus atom contains 15 electrons and has an electronic configuration of the outer valence level similar to nitrogen (3s 2 3p 3), but phosphorus has less pronounced nonmetallic properties compared to nitrogen, which is explained by the presence of a free d-orbital, a larger atomic radius and lower ionization energy .

When reacting with other chemical elements, the phosphorus atom can exhibit an oxidation state from +5 to -3 (the most typical oxidation state is +5, the rest are quite rare).

+5 - phosphorus oxide P 2 O 5 (V); phosphoric acid (H 3 PO 4); phosphates, halides, sulfides of phosphorus V (salts of phosphoric acid);
+3 - P 2 O 3 (III); phosphorous acid (H 3 PO 3); phosphites, halides, sulfides of phosphorus III (salts of phosphorous acid);
0 - P;
-3 - phosphine PH 3; metal phosphides.

In the ground (unexcited) state of the phosphorus atom at the outer energy level there are two paired electrons in the s-sublevel + 3 unpaired electrons in p-orbitals (the d-orbital is free). In the excited state, one electron moves from the s-sublevel to the d-orbital, which expands the valence capabilities of the phosphorus atom.

Rice. Transition of the phosphorus atom to an excited state.

P2

Two phosphorus atoms combine to form a P2 molecule at a temperature of about 1000°C.

At lower temperatures, phosphorus exists in tetraatomic P4 molecules as well as in more stable polymer P∞ molecules.

Allotropic modifications of phosphorus:

White phosphorus- extremely toxic (the lethal dose of white phosphorus for an adult is 0.05-0.15 g) waxy substance with the smell of garlic, colorless, luminescent in the dark (the process of slow oxidation in P 4 O 6); the high reactivity of white phosphorus is explained by weak P-P bonds (white phosphorus has a molecular crystal lattice with the formula P 4, in the nodes of which phosphorus atoms are located), which break quite easily, as a result of which white phosphorus, when heated or during long-term storage, turns into more stable polymer modifications: red and black phosphorus. For these reasons, white phosphorus is stored without access to air under a layer of purified water or in special inert environments.
Yellow phosphorus- a flammable, highly toxic substance, does not dissolve in water, easily oxidizes in air and ignites spontaneously, while burning with a bright green, dazzling flame with the release of thick white smoke.
Red phosphorus- a polymeric, water-insoluble substance with a complex structure that has the least reactivity. Red phosphorus is widely used in industrial production, because it is not so poisonous. Since in the open air red phosphorus, absorbing moisture, gradually oxidizes to form a hygroscopic oxide (“damp”) and forms viscous phosphoric acid, therefore, red phosphorus is stored in a hermetically sealed container. In the case of soaking, red phosphorus is cleaned of phosphoric acid residues by washing with water, then dried and used for its intended purpose.
Black phosphorus- a greasy-to-touch graphite-like substance of gray-black color, with semiconductor properties - the most stable modification of phosphorus with average reactivity.
Metallic phosphorus obtained from black phosphorus under high pressure. Metallic phosphorus conducts electricity very well.

Chemical properties of phosphorus

Of all the allotropic modifications of phosphorus, the most active is white phosphorus (P 4). Often in the equation of chemical reactions we write simply P, not P4. Since phosphorus, like nitrogen, has many variants of oxidation states, in some reactions it is an oxidizing agent, in others it is a reducing agent, depending on the substances with which it interacts.

Oxidative Phosphorus exhibits its properties in reactions with metals that occur when heated to form phosphides:
3Mg + 2P = Mg 3 P 2.

Phosphorus is reducing agent in reactions:

with more electronegative nonmetals (oxygen, sulfur, halogens):
- Phosphorus (III) compounds are formed when there is a lack of oxidizing agent
  4P + 3O 2 = 2P 2 O 3
- phosphorus compounds (V) - with excess: oxygen (air)
  4P + 5O 2 = 2P 2 O 5
with halogens and sulfur, phosphorus forms halides and sulfide of 3- or 5-valent phosphorus, depending on the ratio of reagents, which are taken in deficiency or excess:
- 2P+3Cl 2 (week) = 2PCl 3 - phosphorus (III) chloride
- 2P+3S(week) = P 2 S 3 - phosphorus (III) sulfide
- 2P+5Cl2(g) = 2PCl 5 - phosphorus chloride (V)
- 2P+5S(g) = P 2 S 5 - phosphorus sulfide (V)
with concentrated sulfuric acid:
2P+5H 2 SO 4 = 2H 3 PO 4 +5SO 2 +2H 2 O
with concentrated nitric acid:
P+5HNO 3 = H 3 PO 4 +5NO 2 +H 2 O
with dilute nitric acid:
3P+5HNO 3 +2H 2 O = 3H 3 PO 4 +5NO

Phosphorus acts as both an oxidizing agent and a reducing agent in reactions disproportionation with aqueous solutions of alkalis when heated, forming (except for phosphine) hypophosphites (salts of hypophosphorous acid), in which it exhibits an uncharacteristic oxidation state of +1:
4P 0 +3KOH+3H 2 O = P -3 H 3 +3KH 2 P +1 O 2

YOU MUST REMEMBER: phosphorus does not react with other acids, except for the reactions indicated above.

Production and use of phosphorus

Phosphorus is produced industrially by reducing it with coke from phosphorites (fluorapatates), which include calcium phosphate, by calcining them in electric furnaces at a temperature of 1600°C with the addition of quartz sand:
Ca 3 (PO 4) 2 + 5C + 3SiO 2 = 3CaSiO 3 + 2P + 5CO.

In the first stage of the reaction, under the influence of high temperature, silicon (IV) oxide displaces phosphorus (V) oxide from the phosphate:
Ca 3 (PO 4) 2 + 3SiO 2 = 3CaSiO 3 + P 2 O 5.

Phosphorus (V) oxide is then reduced by coal to free phosphorus:
P 2 O 5 +5C = 2P+5CO.

Application of phosphorus:

pesticides;
matches;
detergents;
paints;
semiconductors.

Phosphorus is a fairly common chemical element on our planet. Its name translates as “luminiferous” because in its pure form it glows brightly in the dark. This element was discovered completely by accident, by the alchemist Henning Brand, when he was trying to extract gold from urine. Thus, phosphorus became the first element that alchemists were able to obtain through their experiments.

Characteristics of phosphorus

It is chemically very active, so in nature it can only be found in the form of minerals - compounds with other elements, of which there are 190 species. The most important compound is calcium phosphate. Many varieties of apatites are now known, the most common of which is fluorapatite. Sedimentary rocks - phosphorites - are composed of various types of apatites.

Phosphorus is very important for living organisms, since it is part of both plant and animal protein in the form of various compounds.

In plants, this element is found mainly in seed proteins, and in animal organisms - in various proteins in the blood, milk, brain cells and large amounts of phosphorus are found in the form of calcium phosphate in the bones of vertebrates.

Phosphorus exists in three allotropic modifications: white phosphorus, red and black. Let's take a closer look at them.

White phosphorus can be obtained by quickly cooling its vapor. Then a solid crystalline substance is formed, which in its pure form is absolutely colorless and transparent. White phosphorus sold for sale is usually slightly yellowish in color and closely resembles wax in appearance. In the cold, this substance becomes brittle, and at temperatures above 15 degrees it becomes soft and can be easily cut with a knife.

White phosphorus does not dissolve in water, but it responds well to organic solvents. In air it oxidizes very quickly (starts to burn) and at the same time glows in the dark. Actually, ideas about a luminous substance and detective stories about it are associated specifically with white phosphorus. It is a strong poison that is lethal even in small doses.

Red phosphorus is a dark red solid whose properties are strikingly different from those described above. It oxidizes in air very slowly, does not glow in the dark, lights up only when heated, it cannot be dissolved in organic solvents, and it is not poisonous. With strong heating, in which there is no access to air, it, without melting, turns into steam, from which, when cooled, white phosphorus is obtained. When both elements burn, phosphorus oxide is formed, which proves the presence of the same element in their composition. In other words, they are formed by one element - phosphorus - and are its allotropic modifications.

Black phosphorus is obtained from white phosphorus at 200 degrees Celsius under high pressure. It has a layered structure, a metallic luster and is similar in appearance to graphite. Of all the solid types of this substance, it is the least active.

Phosphorus is believed to be a glow-in-the-dark mineral that is poisonous and flammable. But this is only part of the truth about this amazing element. Phosphorus can also be different, with directly opposite properties.

What is red phosphorus?

Phosphorus can exist in several varieties (allotropic forms), which differ greatly in their physical and chemical properties. The reason for this is differences in structure. For example, the crystal lattice of white phosphorus is molecular, and the lattice of red phosphorus is atomic. Thanks to it, it reacts slowly with other substances and is stable in air under normal conditions (white phosphorus ignites in air). In total, more than twenty modifications have been found in phosphorus, four of which are stable (white, red, black and metallic phosphorus), the rest are unstable.

Red phosphorus is a very interesting substance, a natural inorganic polymer with the formula (P 4)n and a very complex structure of pyramidally linked atoms.

The properties of red phosphorus depend to some extent on the conditions of its production. By changing temperature, light and catalysts, it is possible to create types of red phosphorus with predictable properties.

The discoverer of red phosphorus is the Austrian A. Schrötter, who obtained it by heating a sealed ampoule with white phosphorus and carbon monoxide at a temperature of +500 ° C.

Properties of red phosphorus

Red phosphorus is produced by prolonged heating of white phosphorus at high temperatures (250-300 °C) without access to air. The color of the substance varies from purple-red to violet.

Red phosphorus, unlike its more famous “brother”, white phosphorus, is a solid substance, does not luminesce, and is practically insoluble in anything (neither in water, nor in organic solvents, nor in carbon disulfide). It is not toxic, it ignites spontaneously in air only at a temperature of +240-260 ° C (in fact, it is not the red phosphorus itself that ignites, but its vapors, which, after cooling, turn into white flammable phosphorus).

The density of red phosphorus is higher than that of white phosphorus and is equal to 2.0 - 2.4 g/cm3 (depending on the specific modification).

In air, red phosphorus absorbs moisture and oxidizes, turning into oxide; continuing to absorb moisture, it turns into thick phosphoric acid (“soaks”). In view of this, the reagent should be hermetically sealed, preventing access to air moisture. When heated, red phosphorus does not melt, but sublimes (evaporates). After condensation, the vapor of the substance turns into white phosphorus.

Applications of red phosphorus

Red phosphorus is practically non-toxic and much safer in operation and storage than white phosphorus. Therefore, in the industrial production of phosphides, phosphorus-containing fertilizers, and various derivatives of phosphoric acid, red phosphorus is most often used.

Red phosphorus itself is mainly used to make matches. It is included in the “grating” mixture, which is applied to the box. It is also used in lubricants, incendiary compositions, fuel, and in the production of incandescent lamps.

Don't know where to buy red phosphorus?

You can buy red phosphorus and various other chemicals at one of the largest laboratory equipment stores, Prime Chemicals Group. We have affordable prices and convenient delivery throughout Moscow and the region, and qualified managers will help you make a choice.

Phosphorus is an important component of living and inanimate nature. It is found in the depths of the Earth, water and in our body, and Academician Fersman even nicknamed it “the element of life and thought.” Despite its usefulness, white phosphorus can be extremely dangerous and poisonous. Let's talk in more detail about its characteristics.

Opening an element

The history of the discovery of phosphorus began with alchemy. Since the 15th century, European scientists have been eager to find the philosopher's stone or the “great elixir” with which they can turn any metals into gold.

In the 17th century, alchemist Hennig Brand decided that the path to the “magic reagent” lay through urine. It is yellow, which means it contains gold or is somehow connected with it. The scientist carefully collected material, defended it, and then distilled it. Instead of gold, he received a white substance that glowed in the dark and burned well.

Brand called the discovery “cold fire.” Later, the Irish alchemist Robert Boyle and the German Andreas Maggraf came up with the idea of obtaining phosphorus in a similar way. The latter also added coal, sand and the mineral phosgenite to the urine. Subsequently, the substance was named phosphorus mirabilis, which translated as “miraculous carrier of light.”

Luminiferous element

The discovery of phosphorus became a real sensation among alchemists. Some tried every now and then to buy the secret of obtaining the substance from Brand, others tried to get there on their own. In the 18th century, it was proven that the element was contained in the bone remains of organisms, and several factories for its production soon opened.

The French physicist Lavoisier proved that phosphorus is a simple substance. In the periodic table it is number 15. Together with nitrogen, antimony, arsenic and bismuth, it belongs to the group of pnictides and is characterized as a non-metal.

The element is quite common in nature. In percentage terms, it ranks 13th in the mass of the earth’s crust. Phosphorus actively interacts with oxygen and is not found in free form. It exists in numerous minerals (more than 190), such as phosphorites, apatites, etc.

White phosphorus

Phosphorus exists in several forms or allotropes. They differ from each other in density, color and chemical properties. There are usually four main forms: white, black, red and metallic phosphorus. Other modifications are only a mixture of the above.

White phosphorus is very unstable. Under normal light conditions it quickly turns red, but high pressure turns it black. Its atoms are arranged in the form of a tetrahedron. It has a crystalline molecular lattice, with the molecular formula P4.

I also highlight yellow phosphorus. This is not another modification of the substance, but the name of unrefined white phosphorus. It can have either a light or dark brown tint and is characterized by strong toxicity.

Properties of white phosphorus

The consistency and appearance of the substance resembles wax. It has a garlicky smell and is greasy to the touch. Phosphorus is soft (it can be cut with a knife without much effort) and is deformable. After cleansing it becomes colorless. Its transparent crystals shimmer iridescently in the sun and look like diamonds.

It melts at 44 degrees. The activity of the substance manifests itself even at room temperature. The main characteristic of phosphorus is its ability to chemiluminescent or glow. Oxidizing in air, it emits a white-green light, and over time it spontaneously ignites.

The substance is practically insoluble in water, but can burn in it with prolonged contact with oxygen. It dissolves well in organic solvents, such as carbon disulfide, liquid paraffin and benzene.

Application of phosphorus

Man has “tamed” phosphorus for both peaceful and military purposes. The substance is used to produce phosphoric acid, which is used for fertilizers. Previously, it was widely used for dyeing wool and making photosensitive emulsions.

White phosphorus is not widely used. Its main value is flammability. Thus, the substance is used for incendiary ammunition. This type of weapon was relevant during both World Wars. It was used in the Gaza war in 2009, as well as in Iraq in 2016.

Red phosphorus is used more widely. It is used to make fuel, lubricants, explosives and match heads. Various phosphorus compounds are used in industry in water softeners and added to passivation agents to protect metal from corrosion.

Content in the body and effect on humans

Phosphorus is one of the vital elements for us. In the form of compounds with calcium, it is present in the teeth and skeleton, giving bones hardness and strength. The element is present in ATP and DNA compounds. It is essential for brain function. Being in nerve cells, it promotes the transmission of nerve impulses.

Phosphorus is found in muscle tissue. It is involved in the process of converting energy from proteins, fats and carbohydrates entering the body. The element maintains the acid-base balance in cells, and their division occurs. It promotes metabolism and is essential during body growth and recovery.

However, phosphorus can be dangerous. White phosphorus itself is very toxic. Doses above 50 milligrams are fatal. Phosphorus poisoning is accompanied by vomiting, headache and stomach pain. Contact of the substance with the skin causes burns that heal very slowly and painfully.

Excess phosphorus in the body leads to brittle bones, cardiovascular diseases, bleeding, and anemia. The liver and digestive system also suffer from phosphorus oversaturation.