Phosphorus release. Atomic and molecular mass of phosphorus. Interaction of nitrogen with nonmetals
Phosphorus was discovered in 1669 by the Hamburg alchemist Hennig Brand, who experimented with the evaporation of human urine in an attempt to obtain the philosopher's stone. The substance formed after numerous manipulations turned out to be similar to wax, burning unusually brightly, with flickering. The new substance was given a name phosphorus mirabilis(from Latin miraculous fire bearer). A few years later, phosphorus was obtained by Johann Kunkel, and also, independently of the first two scientists, by R. Boylem.
Phosphorus is an element of group XV of period III of the periodic table of chemical elements D.I. Mendeleev, with atomic number 15 and atomic mass 30,974. The accepted designation is R.
Being in nature
Phosphorus is found in sea water and the earth's crust mainly in the form of minerals, of which there are about 190 (the most important are apatite and phosphorite). It is part of all parts of green plants, proteins, and DNA.
Phosphorus is a non-metal with high chemical activity and is practically never found in free form. There are four known modifications of phosphorus - red, white, black and metallic.
Daily phosphorus requirement
For normal functioning, the adult body must receive 1.0-2.0 g of phosphorus per day. For children and adolescents, the norm is 1.5-2.5 g, for pregnant and lactating women it increases to 3.0-3.8 g (calorizator). The daily requirement for phosphorus increases during regular sports training and physical activity.
The main suppliers of phosphorus are fish and seafood, cottage cheese, cheese, nuts, legumes and cereals. A sufficient amount of phosphorus is contained in both, and, berries, mushrooms and meat, and.
Signs of phosphorus deficiency
An insufficient amount of phosphorus in the body is characterized by fatigue and weakness, and may be accompanied by loss of appetite and attention, frequent colds, anxiety and a feeling of fear.
Signs of excess phosphorus
Signs of excess phosphorus in the body are bleeding and hemorrhage, anemia develops, and kidney stones occur.
Phosphorus ensures normal growth of bone and dental tissues of the body, maintains them in a healthy state, is also involved in protein synthesis, and plays an important role in the metabolism of fats, proteins and carbohydrates. Without phosphorus, muscles cannot function and mental activity does not occur.
Phosphorus digestibility
When taking mineral complexes, it is worth remembering the best balance of phosphorus and (3:2), and also that excessive amounts slow down the process of phosphorus absorption.
Phosphorus is widely used in industry and agriculture, primarily due to its flammability. It is used in the production of fuel, matches, explosives, phosphorus fertilizers and protection of metal surfaces from corrosion.
Forest-steppe soils
characterized by a humus content of 1.78-2.46%.Powerful black soils
contain 0.81-1.25% humus matter.Ordinary chernozems
contain 0.90-1.27% humus matter.Leached chernozems
contain 1.10-1.43% of humic matter.Dark chestnut soils contain
in humic matter 0.97-1.30%.Role in the plant
Biochemical functions
Oxidized phosphorus compounds are necessary for all living organisms. None living cell cannot exist without them.
In plants, phosphorus is found in organic and mineral compounds. At the same time, the content of mineral compounds ranges from 5 to 15%, organic compounds - 85-95%. Mineral compounds are represented by potassium, calcium, ammonium and magnesium salts of orthophosphoric acid. Mineral phosphorus of plants is a reserve substance, a reserve for the synthesis of phosphorus-containing organic compounds. It increases the buffering capacity of cell sap, maintains cell turgor and other equally important processes.
Organic compounds - nucleic acids, adenosine phosphates, sugar phosphates, nucleoproteins and phosphatoproteins, phosphatides, phytin.
In first place in importance for plant life are nucleic acids (RNA and DNA) and adenosine phosphates (ATP and ADP). These compounds are involved in many vital processes of the plant organism: protein synthesis, energy metabolism, transmission of hereditary properties.
Nucleic acids
Adenosine phosphates
The special role of phosphorus in plant life is its participation in the energy metabolism of the plant cell. the main role in this process belongs to adenosine phosphates. They contain phosphoric acid residues linked by high-energy bonds. When hydrolyzed, they are capable of releasing significant amounts of energy.
They represent a kind of energy accumulator, supplying it as needed to carry out all processes in the cell.
There are adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP). The latter significantly exceeds the first two in energy reserves and occupies a leading role in energy metabolism. It consists of adenine (a purine base) and a sugar (ribose), as well as three phosphoric acid residues. ATP synthesis occurs in plants during respiration.
Phosphatides
Phosphatides, or phospholipids, are esters of glycerol, high molecular weight fatty acids and phosphoric acid. They are part of phospholipid membranes and regulate the permeability of cellular organelles and plasmalemma to various substances.
Cytoplasm of all plant cells contains a member of the phosphatide group lecithin. This is a derivative of diglyceride phosphoric acid, a fat-like substance containing 1.37% .
Sugar phosphates
Sugar phosphates, or phosphorus esters of sugars, are present in all plant tissues. More than a dozen compounds of this type are known. They play an important role in the processes of respiration and photosynthesis in plants. The formation of sugar phosphates is called phosphorylation. The content of sugar phosphates in the plant, depending on age and nutritional conditions, varies from 0.1 to 1.0% of dry weight.
Fitin
Phytin is a calcium-magnesium salt of inositol phosphoric acid, containing 27.5%. It ranks first in terms of content in plants among other phosphorus-containing compounds. Phytin is present in young organs and tissues of plants, especially in seeds, where it serves as a reserve substance and is used by seedlings during the germination process.
Main functions of phosphorus
Most phosphorus is present in the reproductive organs and young parts of plants. Phosphorus is responsible for accelerating the formation of plant root systems. The main amount of phosphorus is consumed in the first phases of development and growth. Phosphorus compounds have the ability to easily move from old tissues to young ones and be reused (recycled).
Phosphorus is a chemical element with atomic number 15. It is located in group V of the periodic table of D.I. Mendeleev. Chemical formula phosphorus R.
Phosphorus gets its name from the Greek phosphoros, which means “light-bearing”.
Phosphorus is quite common in the earth's crust. Its content is 0.08-0.09% of the total mass earth's crust. And sea water contains 0.07 mg/l of phosphorus.
Phosphorus has high chemical activity, so it is not found in a free state. But it forms almost 190 minerals. Phosphorus is called the element of life. It is found in green plants, animal tissues, proteins and other essential chemical compounds.
Phosphorus modifications
It is known that some chemical elements can exist in the form of two or more simple substances that differ in their structure and properties. This phenomenon is called allotropy. So, phosphorus has several allotropic modifications. All these modifications are different in their properties. The most common are white phosphorus, yellow phosphorus, red phosphorus, black phosphorus.
White phosphorus - a simple white substance. Its molecular formula is P4. By appearance white phosphorus is similar to paraffin. It deforms even with little effort and is easily cut with a knife. In the dark, a pale green glow emanating from phosphorus is noticeable. This phenomenon is called chemiluminescence.
White phosphorus - chemically active substance. It is easily oxidized by oxygen and easily dissolves in organic solvents. Therefore, it is stored in special inert environments that do not enter into chemical reactions. White phosphorus melts at a temperature of +44.1 °C. White phosphorus is a very toxic substance.
Yellow phosphorus – This is unrefined white phosphorus, or white phosphorus with impurities. Melting point +34 °C, boiling point +280 °C. Like white phosphorus, yellow phosphorus does not dissolve in water. In air it oxidizes and is highly flammable. It is also characterized by the phenomenon of chemiluminescence.
Red phosphorus obtained by heating white phosphorus to high temperatures. Formula of red phosphorus Pn. This is a polymer complex structure. Depending on the production conditions, the color of red phosphorus can vary from light red to dark brown. Chemically, red phosphorus is much less active than white phosphorus. It dissolves only in molten lead and bismuth. Does not ignite in air. This can only happen when heated to 240-250 o C when sublimating it into the white form of phosphorus. But it can spontaneously ignite upon impact or friction. The phenomenon of chemiluminescence is not observed in red phosphorus. It is insoluble in water, benzene, and carbon disulfide. Soluble only in phosphorus tribromide. When stored in air, it gradually oxidizes. Therefore, store it in a closed, airtight container.
Red phosphorus is almost non-toxic. Therefore, it is used in the production of matches.
Black phosphorus looks like graphite. Black phosphorus was first obtained in 1914 from white phosphorus at a pressure of 20 thousand atmospheres (2 10 9 Pa) and a temperature of 200 o C. Black phosphorus melts at a temperature of 1000 o C and a pressure of 18 10 5 Pa. Black phosphorus does not dissolve either in input or in organic solvents. It begins to burn only if it is heated to a temperature of +400 o C in pure oxygen. Black phosphorus has the properties of semiconductor materials.
Chemical properties of elemental phosphorus
1. Elemental phosphorus is oxidized by oxygen
In an environment with excess oxygen
4P + 5O 2 → 2P 2 O 5
With a lack of oxygen
4P + 3O 2 → 2P 2 O 3
2. Interacts with metals, forming phosphides when heated
3Mg + 2P → Mg 3 P 2
3. Interacts with non-metals
2P + 5Cl 2 → 2PCl 5
4. At a temperature of +500 o C interacts with water vapor
8Р +12Н 2 О → 5РН 3 + 3Н 3 РО 4
Application of phosphorus
The main consumer of phosphorus is Agriculture. A large amount of the resulting phosphorus is used for the production of phosphate fertilizers: phosphate rock, simple and double superphosphates, complex nitrogen-phosphorus fertilizers. Phosphorus is widely used in the production of synthetic detergents, phosphate glasses, and for processing and dyeing natural and synthetic fibers. In medicine, phosphorus preparations are used as medicines.
He achieved great success in studying the properties of phosphorus in the early 70s of the 18th century. the great French chemist Antoine Laurent Lavoisier. By burning phosphorus with other substances in a closed volume of air, Lavoisier proved that phosphorus is an independent element, and air has complex composition and is composed of at least two components - oxygen and nitrogen. “In this way, for the first time, he put on its feet all chemistry, which in its phlogistic form stood on its head.” This is how F. Engels wrote about Lavoisier’s works in the preface to the second volume of Capital.
In 1799, Dondonald proved that phosphorus compounds are necessary for the normal development of plants.
In 1839, another Englishman, Laws, was the first to obtain superphosphate - a phosphorus fertilizer that is easily absorbed by plants.
In 1847, the German chemist Schrötter, heating white phosphorus without access to air, obtained a new variety (allotropic modification) of element No. 15 - red phosphorus, and already in the 20th century, in 1934, the American physicist P. Bridgman, studying the influence of high pressure on various substances, isolated black phosphorus, similar to graphite. These are the main milestones in the history of element No. 15. Now let us trace what followed each of these discoveries.
“In 1715, Gensing established the presence of phosphorus in brain tissue... In 1769, Hahn proved that bones contain a lot of phosphorus”
Phosphorus is an analogue of nitrogen. Although physical and Chemical properties These elements are very different, but they also have something in common, in particular, that both of these elements are absolutely necessary for animals and plants. Academician A.E. Fersman called phosphorus “the element of life and thought,” and this definition can hardly be classified as literary exaggeration. Phosphorus is found in literally all organs of green plants: stems, roots, leaves, but most of all in fruits and seeds. Plants accumulate phosphorus and supply it to animals.
In animals, phosphorus is concentrated mainly in the skeleton, muscles and nerve tissue. Among human food products, the yolk of chicken eggs is especially rich in phosphorus.
The human body contains on average about 1.5 kg of element No. 15. Of this amount, 1.4 kg is in bones, about 130 g in muscles and 12 g in nerves and brain. Almost all the most important physiological processes occurring in our body are associated with the transformations of organophosphorus substances. Phosphorus is found in bones mainly in the form of calcium phosphate. Tooth enamel is also a phosphorus compound, which in composition and crystal structure corresponds to the most important phosphorus mineral, apatite Ca 5 (PO 4) 3 (F, Cl).
Naturally, like any vital element, phosphorus undergoes a cycle in nature. Plants take it from the soil, and from plants this element enters the bodies of humans and animals. Phosphorus returns to the soil with excrement and when corpses rot. Phosphorobacteria convert organic phosphorus into inorganic compounds. However, per unit time, significantly more phosphorus is removed from the soil than enters the soil. The world harvest now annually removes more than 3 million tons of phosphorus from the fields.
Naturally, to obtain sustainable yields, this phosphorus must be returned to the soil, and therefore it is not surprising that the world production of phosphate rock is now significantly more than 100 million tons per year.
“...Proust and Klaproth proved that phosphorus is widely distributed in the earth’s crust, mainly in the form of calcium phosphate”
In the earth's crust, phosphorus occurs exclusively in the form of compounds. These are mainly poorly soluble salts of orthophosphoric acid; The cation most often is calcium ion. Phosphorus accounts for 0.08% of the weight of the earth's crust. In terms of prevalence, it ranks 13th among all elements. Phosphorus is contained in at least 190 minerals, the most important of which are: fluorapatite Ca 5 (PO 4) 3 F, hydroxyapatite Ca 5 (PO 4) 3 OH, phosphorite Ca 3 (PO 4) 2 with impurities.
Less common are vivianite Fe 3 (PO 4) 2 *8H 2 O, monazite (Ce, La)PO 4, amblygonite LaAl(PO 4)F, triphylite Li(Fe, Mn)PO 4 and even more rarely xenotime YPO 4 and torbernite Cu (UO 2) 2 2 *12H 2 O.
Phosphorus minerals are divided into primary and secondary. Of the primary ones, apatites are especially common, often found among rocks of igneous origin. These minerals were formed during the formation of the earth's crust.
Unlike apatites, phosphorites occur among rocks of sedimentary origin, formed as a result of the death of living beings. These are secondary minerals. Phosphorus is found in meteorites in the form of iron, cobalt, and nickel phosphides. Of course, this common element is also found in sea water (6 * 10 -6%).
“Lavoisier proved that phosphorus is an independent chemical element...”
Phosphorus is a non-metal (what was previously called a metalloid) of medium activity. The outer orbit of the phosphorus atom contains five electrons, three of which are unpaired. Therefore, it can exhibit valences of 3-, 3+ and 5+.
In order for phosphorus to exhibit valency 5+, some kind of effect on the atom is necessary, which would turn the two paired electrons of the last orbit into unpaired ones. Phosphorus is often called a multifaceted element. Indeed, under different conditions it behaves differently, exhibiting either oxidative or reducing properties. The versatility of phosphorus also includes its ability to exist in several allotropic modifications.
Perhaps the most famous modification of element No. 15 is waxy, white or yellow phosphorus. It was Brand who discovered it, and thanks to its properties the element received its name: in Greek “phosphorus” means luminous, luminiferous. The white phosphorus molecule consists of four atoms arranged in the shape of a tetrahedron. Density 1.83, melting point 44.1°C. White phosphorus is poisonous and easily oxidizes. Soluble in carbon disulfide, liquid ammonia and SO 2, benzene, ether. Almost insoluble in water.
When heated without access to air above 250°C, white phosphorus turns into red. This is already a polymer, but not a very ordered structure. The reactivity of red phosphorus is significantly less than that of white phosphorus. It does not glow in the dark, does not dissolve in carbon disulfide, and is not poisonous. Its density is much greater, its structure is fine-crystalline.
Less known are other, even more high-molecular modifications of phosphorus - violet, brown and black, which differ from each other in molecular weight and degree of order of macromolecules. Black phosphorus, first obtained by P. Bridgman under high pressure conditions (200 thousand atm at a temperature of 200°C), is more reminiscent of graphite than white or red phosphorus. These modifications are laboratory exotics and, unlike white and red phosphorus, have not yet found practical application.
Speaking of applications of elemental phosphorus; Its main consumers are the production of matches, metallurgy, and chemical production. In the recent past, part of the resulting elemental phosphorus was spent at military enterprises; it was used to prepare smoke and incendiary compositions.
Metallurgists usually strive to get rid of phosphorus impurities in the metal - it worsens the mechanical properties, but sometimes phosphorus is introduced into alloys deliberately. This is done when it is necessary for the metal to expand slightly when solidifying and accurately take on the outline of the shape. Phosphorus is also widely used in chemistry. Part of it is used for the preparation of phosphorus chlorides needed in the synthesis of certain organic preparations; The stage of production of elemental phosphorus is also present in some technological schemes for the production of concentrated phosphorus fertilizers.
Now about its connections
- Phosphoric anhydride P 2 O 5 is an excellent desiccant that greedily absorbs water from the air and other substances. The P 2 O 5 content is the main criterion for the value of all phosphate fertilizers.
- Phosphoric acids, primarily orthophosphoric acid H 3 PO 4 , are used in the basic chemical industry. Salts of phosphoric acids are primarily phosphorus fertilizers (a special discussion about them) and alkali metal phosphates necessary for the production of detergents.
- Phosphorus halides (mainly the chlorides PCl 3 and PCl 5) are used in the organic synthesis industry.
- Of the compounds of phosphorus with hydrogen, the most famous is phosphine PH3 - a highly poisonous colorless gas with a garlicky odor.
- Among phosphorus compounds, a special place belongs to organophosphorus compounds. Most of them have biological activity. Therefore, some organophosphorus compounds are used as medicines, others as pest control agents.
An independent class of substances consisted of phosphonitrile chlorides - compounds of phosphorus with nitrogen and chlorine. The phosphonitrile chloride monomer is capable of polymerization. With increasing molecular weight, the properties of substances of this class change, in particular, their solubility in organic liquids decreases noticeably. When the molecular weight of the polymer reaches several thousand, a rubber-like substance is obtained - the only rubber so far that contains no carbon at all. Further increase in molecular weight leads to the formation of hard plastic-like substances. “Carbon-free rubber” has significant heat resistance: it begins to break down only at 350°C.
“In 1839, the Englishman Laws was the first to obtain superphosphate - a phosphorus fertilizer that is easily absorbed by plants.” In order for plants to absorb phosphorus, it must be part of a soluble compound. To obtain these compounds, calcium phosphate and sulfuric acid mixed in such proportions that for one gram molecule of phosphate there are two gram molecules of acid. As a result of the interaction, sulfate and soluble calcium dihydrogen phosphate are formed: Ca 3 (PO 4) 2 + 2H 2 SO 4 → 2CaSO 4 + Ca(H 2 PO 4) 2.
A mixture of these two salts is known as superphosphate. In this mixture, calcium sulfate from the point of view of agrochemistry is ballast, but it is usually not separated, since this operation is costly and greatly increases the cost of fertilizer. Simple superphosphate contains only 14-20% P 2 O 5. A more concentrated phosphorus fertilizer is double superphosphate. It is obtained by reacting calcium phosphate with phosphoric acid: Ca 3 (PO 4) 2 + 4H 3 PO 4 3Ca(H 2 PO 4) 2.
Double superphosphate contains 40-50% P 2 O 5. In fact, it would be more correct to call it triple: it is three times richer in phosphorus than simple superphosphate. Sometimes CaHPO 4 *H 2 O precipitate is used as a phosphorus fertilizer, which is obtained by reacting phosphoric acid with hydroxide or calcium carbonate. This fertilizer contains 30-35% P 2 O 5.
With the explored reserves of phosphorus raw materials in our country, as well as throughout the world, the situation is not entirely favorable. Academician S.I. Volfkovich from the rostrum of the IX Mendeleev Congress on General and Applied Chemistry said: “If the raw material base of the nitrogen industry is the air ocean, water and natural gas- does not limit the scale of new construction, but the deposits explored to date potassium salts ensure the development of the production of potash fertilizers for more than a millennium, then the reserves of domestic phosphorus raw materials studied to date, with the planned large volumes, fertilizer production will be enough for only a few decades.”
In general, this statement is true today, despite the fact that the scale of production of phosphate fertilizers has increased significantly: in 1980, the USSR produced more than 30 million tons of phosphate fertilizers and 4.4 million tons of phosphate rock in 1965 were 8.04 and 3.24 million tons, respectively.
Phosphorus remains the limiting element of agrochemistry today, although there are opportunities for further expansion of the production of phosphate fertilizers. A lot of additional phosphorus can be obtained through complex processing of mineral raw materials, bottom sea sediments and more detailed geological exploration. Consequently, we have no special grounds for pessimism, especially since Russia ranks first in the world in terms of recorded reserves of phosphorus ores. Nevertheless, it is necessary to search for new deposits and develop methods for producing phosphate fertilizers from poorer ores. Necessary for the future, because phosphorus - “the element of life and thought” - will always be needed by humanity.
