Phosphorus is known in several allotropic modifications: white, red, purple and black. In laboratory practice one encounters white and red modifications.
White phosphorus- solid substance. Under normal conditions it is yellowish, soft and appearance looks like wax. It oxidizes and ignites easily. White phosphorus is poisonous and leaves painful burns on the skin. White phosphorus comes on sale in the form of sticks of different lengths with a diameter of 0.5-2 cm.
White phosphorus easily oxidizes, and therefore it is stored under water in carefully sealed dark glass vessels in dimly lit and not very cold rooms (to avoid cracking of the jars due to freezing of water). The amount of oxygen contained in water and oxidizing phosphorus is very small; it is 7-14 mg per liter of water.
When exposed to light, white phosphorus turns into red.
With slow oxidation, white phosphorus glows, and with vigorous oxidation, it ignites.
White phosphorus is taken with tweezers or metal tongs; Under no circumstances should you touch it with your hands.
In case of a burn with white phosphorus, wash the burned area with a solution of AgNO 3 (1:1) or KMnO 4 (1:10) and apply a wet bandage soaked in the same solutions or a 5% solution of copper sulfate, then the wound is washed with water and, after smoothing the epidermis, applied Vaseline bandage with methyl violet. For severe burns, consult a doctor.
Solutions of silver nitrate, potassium permanganate and copper sulfate oxidize white phosphorus and thereby stop its damaging effect.
In case of white phosphorus poisoning, take a teaspoon of 2% copper sulfate solution orally until vomiting occurs. Then, using the Mitscherlich test based on luminescence, the presence of phosphorus is determined. To do this, water acidified with sulfuric acid is added to the poisoned person’s vomit and distilled in the dark; When the phosphorus content is observed, vapor glow is observed. The device used is a Wurtz flask, to the side tube of which a Liebig refrigerator is connected, from where the distilled products enter the receiver. If phosphorus vapor is directed into a solution of silver nitrate, a black precipitate of metallic silver precipitates, formed according to the equation given in the experiment of the reduction of silver salts with white phosphorus.
Already 0.1 G white phosphorus is a lethal dose for an adult.
Cut white phosphorus with a knife or scissors in a porcelain mortar under water. When using water at room temperature, phosphorus crumbles. Therefore, it is better to use warm water, but not higher than 25-30°. After cutting the phosphorus in warm water, it is transferred to cold water or cooled with a stream of cold water.
White phosphorus is a highly flammable substance. It ignites at a temperature of 36-60°, depending on the concentration of oxygen in the air. Therefore, when conducting experiments, in order to avoid an accident, it is necessary to take into account every grain of it.
Drying of white phosphorus is done by quickly applying thin asbestos or filter paper to it, avoiding friction or pressure.
If phosphorus ignites, it is extinguished with sand, a wet towel or water. If burning phosphorus is on a sheet of paper (or asbestos), this sheet must not be touched, since molten burning phosphorus can easily be spilled.
White phosphorus melts at 44° and boils at 281°. White phosphorus is melted underwater, since molten phosphorus ignites in contact with air. By fusion and subsequent cooling, white phosphorus can be easily recovered from waste. To do this, white phosphorus waste from various experiments, collected in a porcelain crucible with water, is heated in a water bath. If the formation of a crust is noticeable on the surface of the molten phosphorus, add a little HNO 3 or a chromium mixture. The crust is oxidized, small grains merge into a total mass and, after cooling with a stream of cold water, one piece of white phosphorus is obtained.
Residues of phosphorus should never be thrown into the sink, since, accumulating in the elbow bends of the drain pipes, it can cause burns to repair workers.
Experience. Melting and supercooling of molten white phosphorus. A pea-sized piece of white phosphorus is placed in a test tube with water. The test tube is placed in a glass filled almost to the top with water and secured in a vertical position in a tripod clamp. The glass is slightly heated and using a thermometer, the temperature of the water in the test tube is determined at which phosphorus melts. After melting is completed, the test tube is transferred to a glass with cold water and observe the solidification of phosphorus. If the test tube is stationary, then at temperatures below 44° (up to 30°) white phosphorus remains in a liquid state.
The liquid state of white phosphorus, cooled below its melting point, is a state of supercooling.
After the end of the experiment, to make it easier to extract phosphorus, it is melted again and the test tube is immersed with the hole up in an inclined position in a vessel with cold water.
Experience. Attaching a piece of white phosphorus to the end of the wire. To melt and solidify white phosphorus, use a small porcelain crucible with phosphorus and water; it is placed in a glass with warm and then cold water. For this purpose, take iron or copper wire with a length of 25-30 cm and diameter 0.1-0.3 cm. When the wire is immersed in solidifying phosphorus, it easily attaches to it. In the absence of a crucible, a test tube is used. However, due to the insufficiently smooth surface of the test tube, it is sometimes necessary to break it in order to extract phosphorus. To remove white phosphorus from the wire, immerse it in a glass of warm water.
Experience. Determination of the specific gravity of phosphorus. At 10° the specific gravity of phosphorus is 1.83. Experience makes it possible to verify that white phosphorus is heavier than water and lighter than concentrated H 2 SO 4.
When a small piece of white phosphorus is introduced into a test tube with water and concentrated H 2 SO 4 (specific gravity 1.84), it is observed that the phosphorus sinks in the water, but floats on the surface of the acid, melting due to the heat released when concentrated H 2 SO is dissolved 4 in water.
To pour concentrated H 2 SO 4 into a test tube with water, use a funnel with a long and narrow neck that reaches the end of the test tube. Pour the acid and remove the funnel from the test tube carefully so as not to cause mixing of the liquids.
At the end of the experiment, the contents of the test tube are stirred with a glass rod and cooled from the outside with a stream of cold water until the phosphorus hardens so that it can be removed from the test tube.
When using red phosphorus, it is observed that it sinks not only in water, but also in concentrated H 2 SO 4, since its specific gravity (2.35) is greater than the specific gravity of both water and concentrated sulfuric acid.
WHITE PHOSPHORUS, GLOW
Due to the slow oxidation that occurs even at ordinary temperatures, white phosphorus glows in the dark (hence the name “luminiferous”). A greenish luminous cloud appears around a piece of phosphorus in the dark, which, when the phosphorus oscillates, is set into a wave-like motion.
Phosphorescence (glow of phosphorus) is explained by the slow oxidation of phosphorus vapor by oxygen in the air to phosphorous and phosphoric anhydride with the release of light, but without the release of heat. In this case, ozone is released, and the air around it is ionized (see the experiment showing the slow burning of white phosphorus).
Phosphorescence depends on temperature and oxygen concentration. At 10°C and normal pressure, phosphorescence occurs weakly, and in the absence of air it does not occur at all.
Substances that react with ozone (H 2 S, SO 2, Cl 2, NH 3, C 2 H 4, turpentine oil) weaken or completely stop phosphorescence.
The conversion of chemical energy into light energy is called “chemiluminescence.”
Experience. Observation of the glow of white phosphorus. If you observe in the dark a piece of white phosphorus that is in a glass and is not completely covered with water, you will notice a greenish glow. In this case, wet phosphorus slowly oxidizes, but does not ignite, since the water temperature is below the flash point of white phosphorus.
The glow of white phosphorus can be observed after a piece of white phosphorus has been exposed to air for a short time. If you put several pieces of white phosphorus into a flask on glass wool and fill the flask with carbon dioxide, lowering the end of the outlet tube to the bottom of the flask under the glass wool, and then heat the flask slightly by lowering it into a vessel with warm water, then in the dark you can observe the formation of a cold pale greenish flame (you can safely put your hand into it).
The formation of a cold flame is explained by the fact that carbon dioxide escaping from the flask entrains phosphorus vapors, which begin to oxidize upon contact with air at the opening of the flask. In a flask, white phosphorus does not ignite, because it is in an atmosphere of carbon dioxide. At the end of the experiment, the flask is filled with water.
When describing the experience of producing white phosphorus in an atmosphere of hydrogen or carbon dioxide, it was already mentioned that conducting these experiments in the dark makes it possible to observe the glow of white phosphorus.
If you make an inscription with phosphor chalk on a wall, a sheet of cardboard or paper, then thanks to phosphorescence the inscription long time remains visible in the dark.
Such an inscription cannot be made on chalkboard, since after this ordinary chalk does not stick to it and the board has to be washed with gasoline or another stearin solvent.
Phosphorus chalk is obtained by dissolving liquid white phosphorus in molten stearin or paraffin. To do this, approximately two parts by weight of stearin (candle pieces) or paraffin are added to one part by weight of dry white phosphorus in a test tube, the test tube is covered with cotton wool to prevent oxygen from entering, and heated with continuous shaking. After melting is completed, the test tube is cooled with a stream of cold water, then the test tube is broken and the frozen mass is removed.
Phosphorus chalk is stored under water. When using, a piece of such chalk is wrapped in wet paper.
Phosphorus chalk can also be obtained by adding small pieces of dried white phosphorus to paraffin (stearin) melted in a porcelain cup. If the paraffin ignites when adding phosphorus, it is extinguished by covering the cup with a piece of cardboard or asbestos.
After some cooling, the solution of phosphorus in paraffin is poured into dry and clean test tubes and cooled with a stream of cold water until it hardens into a solid mass.
After this, the test tubes are broken, the chalk is removed and stored under water.
SOLUBILITY OF WHITE PHOSPHORUS
White phosphorus is sparingly soluble in water, slightly soluble in alcohol, ether, benzene, xylene, methyl iodide and glycerin; dissolves well in carbon disulfide, sulfur chloride, phosphorus trichloride and tribromide, carbon tetrachloride.
Experience. Dissolution of white phosphorus in carbon disulfide. Carbon disulfide is a colorless, highly volatile, flammable, toxic liquid. Therefore, when working with it, avoid inhaling its vapors and turn off all gas burners.
Three to four pea-sized pieces of white phosphorus are dissolved with gentle shaking in a glass with 10-15 ml carbon disulphide.
If a small piece of filter paper is moistened with this solution and held in air, the paper will ignite after a while. This happens because carbon disulfide evaporates quickly, and the finely ground white phosphorus remaining on the paper quickly oxidizes at normal temperatures and ignites due to the heat generated during oxidation. (It is known that the ignition temperature of various substances depends on the degree of their grinding.) It happens that the paper does not ignite, but only chars. The paper, moistened with a solution of phosphorus in carbon disulfide, is held in air using metal tongs.
The experiment is carried out carefully so that drops of a solution of phosphorus in carbon disulfide do not fall on the floor, on the table, on clothes or on hands.
If the solution gets on your hand, quickly wash it with soap and water, and then with a KMnO 4 solution (to oxidize the white phosphorus particles that get on your hands).
The solution of phosphorus in carbon disulfide remaining after the experiments is not stored in the laboratory, as it can easily ignite.
CONVERTING WHITE PHOSPHORUS TO RED
White phosphorus turns into red according to the equation:
P (white) = P (red) + 4 kcal.
Installation for producing white phosphorus from red: reactor tube 1, tube 2, through which carbon dioxide enters the reactor tube, gas outlet tube 3, through which white phosphorus vapors together with carbon dioxide leave the test tube and are cooled with water
The conversion of white phosphorus to red is greatly accelerated by heating, exposure to light, and the presence of traces of iodine (1 G iodine at 400 G white phosphorus). Iodine, combining with phosphorus, forms iodide phosphorus, in which white phosphorus dissolves and quickly turns into red with the release of heat.
Red phosphorus is obtained by prolonged heating of white phosphorus in a closed vessel in the presence of traces of iodine to 280-340°
When white phosphorus is stored in the light for a long time, it gradually turns into red.
Experience. Obtaining a small amount of red phosphorus from white. In a glass tube 10-12 long closed at one end cm and diameter 0.6-0.8 cm a piece of white phosphorus the size of a grain of wheat and a very small crystal of iodine are introduced. The tube is sealed and suspended in an air bath over a tray of sand, then heated to 280-340° and the transformation of white phosphorus into red is observed.
A partial conversion of white phosphorus to red can also be observed by gently heating a test tube containing a small piece of white phosphorus and a very small crystal of iodine. Before heating begins, the test tube is closed with a swab made of glass (asbestos or ordinary) wool and a tray with sand is placed under the test tube. The test tube is heated for 10-15 minutes (without bringing the phosphorus to a boil) and the transformation of white phosphorus into red is observed.
The white phosphorus remaining in the test tube can be removed by heating with a concentrated alkali solution or by burning.
The transformation of white phosphorus into red can also be observed when a small piece of phosphorus is heated in a test tube in an atmosphere of carbon dioxide to a temperature below boiling.
COMBUSTION OF WHITE PHOSPHORUS
When white phosphorus burns, phosphorus anhydride is formed:
P 4 + 5O 2 = 2 P 2 O 5 + 2 x 358.4 kcal.
You can observe the combustion of phosphorus in air (slow and fast) and under water.
Experience. Slow burning of white phosphorus and air composition. This experiment was not described as a method of obtaining nitrogen, since it does not completely bind the oxygen contained in the air.
The slow oxidation of white phosphorus by atmospheric oxygen occurs in two stages; At the first stage, phosphorous anhydride and ozone are formed according to the equations:
2P + 2O 2 = P 2 O 3 + O, O + O 2 = O 3.
In the second stage, phosphorous anhydride is oxidized to phosphoric anhydride.
The slow oxidation of white phosphorus is accompanied by glow and ionization of the surrounding air.
An experiment showing the slow burning of white phosphorus should last at least three hours. The device required for the experiment is shown in Fig.
A graduated tube with a closed end, containing about 10 ml water. Tube length 70 cm, diameter 1.5-2 cm. After lowering the graduated tube, remove the finger from the hole in the tube, bring the water in the tube and cylinder to the same level, and note the volume of air contained in the tube. Without raising the tube above the water level in the cylinder (so as not to let in additional air), a piece of white phosphorus attached to the end of a wire is introduced into the air space of the tube.
After three to four hours or even two to three days, a rise in water in the tube is noted.
At the end of the experiment, remove the wire with phosphorus from the tube (without raising the tube above the water level in the cylinder), bring the water in the tube and cylinder to the same level and note the volume of air remaining after the slow oxidation of white phosphorus.
Experience shows that as a result of phosphorus binding oxygen, the volume of air decreased by one fifth, which corresponds to the oxygen content in the air.
Experience. Rapid burning of white phosphorus. Due to the fact that when a phosphorus compound reacts with oxygen, it releases large number heat, in air white phosphorus spontaneously ignites and burns with a bright yellowish-white flame, forming phosphorus anhydride - a solid white substance that combines very energetically with water.
It was previously mentioned that white phosphorus ignites at 36-60°. To observe its spontaneous ignition and combustion, a piece of white phosphorus is placed on a sheet of asbestos and covered with a glass bell or a large funnel, on the neck of which a test tube is placed.
Phosphorus can easily be set on fire with a glass rod heated in hot water.
Experience. Comparison of ignition temperatures of white and red phosphorus. At one end of a copper plate (length 25 cm, width 2.5 cm and thickness 1 mm) place a small piece of dried white phosphorus, and pour a small pile of red phosphorus on the other end. The plate is placed on a tripod and at the same time approximately equally burning gas burners are brought to both ends of the plate.
White phosphorus ignites immediately, and red phosphorus only when its temperature reaches approximately 240°.
Experience. Ignition of white phosphorus under water. A test tube of water containing several small pieces of white phosphorus is placed in a glass of hot water. When the water in the test tube heats up to 30-50°, a current of oxygen begins to flow into it through the tube. Phosphorus ignites and burns, scattering bright sparks.
If the experiment is carried out in the glass itself (without a test tube), the glass is placed on a tripod mounted on a tray with sand.
REDUCTION OF SILVER AND COPPER SALT WITH WHITE PHOSPHORUS
Experience. When a piece of white phosphorus is added to a test tube with a solution of silver nitrate, a precipitate of metallic silver is observed (white phosphorus is an energetic reducing agent):
P + 5AgNO 3 + 4H 2 O = H 3 PO 4 + 5Ag + 5HNO 3.
If white phosphorus is added to a test tube with a solution of copper sulfate, then metallic copper precipitates:
2P + 5CuSO 4 + 8H 2 O = 2H 3 PO 4 + 5H 2 SO 4 + 5Cu.
Phosphorus is quite common chemical element on our planet. Its name translates as “luminous” because in 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. Now many varieties of apatites are known, the most common of which is fluorapatite. From Apatity various types sedimentary rocks are composed of phosphorites.
For living organisms, phosphorus has a very important, 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 is formed crystalline substance, 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 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, in organic solvents it cannot be dissolved and 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.
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. On the heads of matches there are mainly complex substances, one of which is potassium chlorate (KClO3), which is capable of spontaneous combustion under 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: lethal dose of about 0.1 g (about the same as in 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. She is good remedy to remove rust.
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.
In a dark room or outside at night, try this simple experiment. Not too hard, so that the match does not light up, strike it on the matchbox. You will notice that a glowing path from the match will be visible on the grater for a while. This glows white phosphorus. But everyone who remembers chemistry lessons high school, may say: “Excuse me, red, not white, phosphorus is used in the production of matches.” Right! There is no white phosphorus in the matchbox grater; there is red phosphorus, which, as a result of the reaction occurring between the red phosphorus located on the surface of the matchbox and the berthollet salt contained in the match head, heats up at the moment of friction and turns into white in a small amount.
Phosphorus can exist in several forms, or, as they say, in several modifications.
White phosphorus is a solid crystalline substance, and in its chemically pure form, white phosphorus crystals are completely colorless, transparent and refract light very well. In the light they quickly turn yellow and lose their transparency. Therefore, under normal conditions, phosphorus is very similar in appearance to wax, but is heavier (density of white phosphorus is 1.84). Phosphorus is brittle in the cold, but at room temperature it is relatively soft and easily cut with a knife. At 44°C white phosphorus melts, and at 280.5°C it boils. White phosphorus, oxidized by oxygen in the air, glows in the dark and easily ignites when slightly heated, for example from friction.
The ignition temperature of completely dry and pure phosphorus is close to the temperature human body. Therefore, it is stored only under water. First world war white phosphorus was used as an incendiary material in artillery shells, aerial bombs, grenades, and bullets.
Red phosphorus, in contrast to white, or yellow, as it is sometimes called, is not poisonous, does not oxidize in air, does not glow in the dark, does not dissolve in carbon disulfide and ignites only at 260 ° C. Red phosphorus is obtained from white phosphorus by prolonged heating without air access at 250-300°C.
History of the discovery of phosphorus
Joseph Wright's painting "The Alchemist Discovering Phosphorus" supposedly describes Hennig Brand's discovery of phosphorus
In search of the elixir of youth and attempts to obtain gold, an alchemist XVII century Genning Brand from Hamburg tried to make a "philosopher's stone" from urine. For this purpose, he evaporated a large amount of it and the syrupy residue obtained after evaporation was subjected to strong calcination in a mixture with sand and charcoal without air access.
As a result, Brand received a substance with extraordinary properties: it glowed in the dark; thrown into boiling water, it released vapors that ignited in the air, releasing thick white smoke that dissolved in the water to form acid.
There was enormous interest in the new substance, and Brand hoped to make a hefty profit from his discovery: it was not for nothing that he was a former Hamburg merchant. Keeping the manufacturing method in the strictest confidence, Brand showed the new substance for money, and sold it to those who wanted it in small portions only for pure gold. After some time, Brand also sold the secret of making phosphorus to the Dresden chemist Kraft, who, like Brand, began to travel around the palaces of influential people, showing phosphorus for money, making a huge fortune.
Miracles with the glow and ignition of phosphorus
After the discovery of phosphorus, its ability to glow in the dark was again used, but for different purposes. This time, representatives of religious cults began to trade in phosphorus. Recipes for using phosphorus were very diverse. For example, a small amount of white phosphorus was added to melted but already thickened wax or paraffin. The resulting mixture was used to mold pencils, which were used to write on the walls of churches and icons. At night, “mysterious inscriptions” were visible. Phosphorus, slowly oxidizing, glowed, and paraffin, protecting it from rapid oxidation, increased the duration of the phenomenon.
White phosphorus was dissolved in benzene or carbon disulfide. The resulting solution was used to moisten the wicks of candles or lamps. After the solvent evaporated, the white phosphorus ignited, and the wick ignited from it. This is how a “miracle” called “self-ignition of candles” was fabricated.
Will-o'-the-wisps in swamps and cemeteries
One of the interesting phosphorus compounds is phosphine gas, the peculiarity of which is that it is highly flammable in air. This property of phosphine explains the appearance of swamp, will-o'-the-wisp, or grave-lights. There really are fires in swamps and fresh graves. This is not fantasy or fiction. On warm, dark nights, pale bluish, faintly flickering lights are sometimes observed on fresh graves. It is the phosphine that “burns.” Phosphine is formed during the decay of dead plant and animal organisms.
IN Paris Library contains a manuscript on alchemy, which describes discovery of phosphorus. According to the document, Alkhid Bakhil was the first to isolate the element in its pure form.
He lived in the 12th century. Phosphorus the man obtained it by distilling urine with lime and. The alchemist called the luminous substance escarbucle. Modern name element was given by Henning Brand.
He connected greek words“light” and “carry.” The German singled white phosphorus in 1669, documenting his merit by speaking to the scientific community.
Henning Brand, like Alchid Bakhil, used evaporated urine, but heated it with white sand. In the 17th century, and even in the 12th, the glow of the resulting substance seemed like a miracle. Among contemporaries for physical properties of phosphorus a different look.
Physical and chemical properties phosphorus
Element phosphorus glows due to oxidation processes. Interaction with oxygen occurs quickly, and spontaneous combustion is possible.
The rapid and abundant release of chemical energy leads to its transformation into light energy. The process takes place even at room temperature.
That's the secret to shining phosphorus. Oxygen reacts most easily with a white modification of the element. It can be confused with wax and candle paraffin. The substance melts already at 44 degrees Celsius.
Properties of phosphorus white color differ from the properties of other modifications of the element. For example, they are not toxic.
Colorless phosphorus is poisonous and insoluble in water. As a rule, it blocks the oxidation of the powder. Without reacting with water, white phosphorus easily dissolves in organic matter, for example, carbon disulfide.
In the first modification substance phosphorus least dense. There are only 1,800 grams per cubic meter. At the same time, the lethal dose for humans is only 0.1 grams.
Even more poisonous yellow phosphorus. In fact, it is a type of white, but not refined. The density of the substance is the same, so is the flammability.
The melting point is slightly lower - 34 degrees. The element boils at 280 Celsius. Due to contaminants, thick smoke is released during combustion. Yellow phosphorus, like white phosphorus, does not react with water.
There is also red phosphorus. It was first received in 1847. The Austrian chemist Schrötter heated the white modification of the element to 500 degrees in an atmosphere of carbon monoxide.
The reaction was carried out in a sealed flask. The resulting type of phosphorus turned out to be thermodynamically stable. The substance dissolves only in some molten metals.
ignite phosphorus atom can only when the atmosphere warms up to 250 degrees Celsius. The alternative is active friction, or a strong blow.
The color of red phosphorus is not only scarlet, but also violet. There is no glow. There is almost no toxicity. The toxic effect of the red modification of the element is minimal. Therefore, scarlet phosphorus is widely used in industry.
The penultimate modification of the element is black. Obtained in 1914, it is the most stable. The substance has a metallic luster. The surface of black phosphorus is shiny, similar to.
The modification is not amenable to any solvent; it ignites only in an atmosphere heated to 400 degrees. Mass of phosphorus black is the greatest, as is the density. The substance is “born” from white at a pressure of 13,000 atmospheres.
If the pressure is brought to extremely high levels, the final, metallic modification of the element appears. Its density reaches almost 4 grams per cubic centimeter.Phosphorus formula does not change, but is transformed crystal lattice. It becomes cubic. The substance begins to conduct electric current.
Application of phosphorus
Phosphorus oxide serves as a smoke-generating agent. When ignited, the yellow modification of the element produces a thick veil, which is useful in the defense industry.
In particular, phosphorus is added to tracer bullets. Leaving a trail of smoke behind them, they allow you to adjust the direction and accuracy of the sends. The “path” is maintained for a kilometer.
In the military industry, phosphorus found a place, as well as an igniter. The element also plays this role for peaceful purposes. Thus, the red modification is used in the manufacture of matches. They are lubricated by steam. phosphorus-sulfur, that is, sulfide of the 15th element.
Phosphorus chloride is needed in the production of plasticizers. This is the name given to additives that increase the plasticity of plastics and other polymers. Farmers also buy chloride. They mix the substance with insecticides.
They are used to destroy pests in fields, in particular insects. Plantings are also sprayed with pesticides. There is already a duet in them calcium-phosphorus or phosphides.
If insects are killed with the help of phosphorus mixtures, then plants are grown. Yes, couples nitrogen-phosphorus And potassium phosphorus– regulars of fertilizers. The 15th element nourishes plantings, accelerates their development, and increases productivity. Phosphorus is also necessary for humans.
About 800 grams of it are hidden in bones, nucleic chains, and proteins. It’s not for nothing that the element was first extracted by distilling urine. The body's reserves require daily replenishment in the amount of 1.2-1.5 grams. They come with seafood, legumes, cheeses and breads.
Phosphorus acids They are also added to products artificially. For what? Dilute phosphoric acid serves as a flavor enhancer for syrups, marmalades and carbonated drinks. If the product contains E338, we're talking about about a compound involving the 15th element of the periodic table.
Application of phosphorus nature did not associate with its glow. Man focused precisely on this property. Thus, the lion's share of the element's reserves goes to the production of paints. Compositions for cars also protect them from corrosion. Paints have also been invented for glossy surfaces. There are options for wood, concrete, plastic.
Many synthetic detergents cannot do without the 15th element. They contain magnesium. Phosphorus binds its ions.
Otherwise, the effectiveness of the compositions is reduced. Without the 15th element, the quality of some steels also decreases. Their basis is iron. Phosphorus– only .
The additive increases the strength of the alloy. In low-alloy steels, phosphorus is needed to facilitate processing and increase corrosion resistance.
Phosphorus mining
In the periodic table, phosphorus is 15th, but in terms of abundance on Earth it is 11th. The substance is not rare even outside the planet. Thus, meteorites contain from 0.02 to 0.94% phosphorus. It was also found in soil samples taken from the Moon.
Earthly representatives of the element are the 200th mineral, created by nature on its basis. Phosphorus is not found in its pure form. Even in the lithosphere it is represented by orthophosphate, that is, it is oxidized to the highest degree.
To isolate the pure element, industrialists work with calcium phosphate. It is obtained from phosphorites and vtorappatites. These are the 2 minerals richest in the 15th element. After the reduction reaction, 100 percent phosphorus remains.
The reducing agent is coke, that is, carbon. Calcium, in this case, is bound with sand. Experts do all this in electric furnaces. That is, the process of phosphorus release is electrothermal.
This is how to obtain white or yellow phosphorus. It all depends on the degree of purification. What needs to be done to convert a product into red, black, metal modifications is described in the chapter “Chemical and physical properties element".
Phosphorus price
There are companies and stores specializing in the supply of chemical raw materials. Phosphorus is usually offered in packages of 500 grams and kilograms. For the red modification weighing 1,000 grams they ask for about 2,000 rubles.
White phosphorus is offered less frequently and is approximately 30-40% cheaper. Black and metal modifications are expensive and are usually sold to order through large manufacturing enterprises.