Phosphorus compounds

The compounds of phosphorus form the basis of many substances, within most important are phosphates. In all forms of life, phosphates play an essential role in energy transfer processes such as metabolism, photosynthesis, nerve function, and muscle action. Nucleic acids, which among other things make up hereditary material (chromosomes), are phosphates, as well as a number of coenzymes. The skeletons of animals are made of calcium phosphate .


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  • 1 Curiosities about the element
    • 1 Most important copies
  • 2 Phosphorus Compounds
  • 3 Health effects
  • 4 Environmental Effects of Phosphorus
  • 5 Phosphorus Cycle
  • 6 External links
  • 7 Sources

Curiosities about the element

Hennig Brand discovered it in 1669 by heating an evaporated urine sample. Its name corresponds to the old one of the planet Venus when it appeared before sunrise. It is not in an elemental state, it is always combined and mainly in the form of phosphates: apatite [Ca 5 (PO 4 ) 3F or Ca 5 (PO 4 ) 3Cl], phosphorite [3Ca3 (PO4) 2.Ca (OH, F, Cl) 2], vivianite [Fe 3 (PO 4 ) 2.8H 2 O], pyromorphite [Pb5 (PO4) 3Cl], turquoise [CuAl 6 (PO4) 4 (OH) 8 .5H 2 O], monazite [CePO 4 ], xenotime [YPO 4 ], ….. It constitutes 0.105% by weight of the bark.

In living beings it is found in marine microorganisms, vertebrate bones and teeth in the form of calcium phosphate. The guano of seabirds and some ferrous minerals contain it.

There are several methods, but it is obtained mainly by electrochemical methods in a dry atmosphere from ground mineral (phosphate) mixed with coke and sand and heated to 1400ºC in an electric or fuel furnace. The exhaust gases are filtered and cooled to around 50ºC, which condenses the white phosphorous that is collected under water or phosphoric acid. Gently heating it transforms into red phosphorus.

There are at least 6 classes of phosphorus (allotropes); the most important are: white (or yellow), red, black and purple. The differences between the modifications are clearer than those between the alkali metals.

Ordinary phosphorus is a waxy white solid; when it is pure it is colorless and transparent. In recent cut it appears yellowish. In all states of aggregation, the structural unit is P4. It also has two modifications: a-P4 (cubic) and b-P4 (rhombohedral) with a change temperature of -3.8ºC. It is insoluble in water and soluble in carbon disulfide. Burns spontaneously in air with a yellowish-white flame, producing white vapors of diphosphorous pentaoxide (P 2 O 5). White phosphorus must be stored in water, since in air it is a very dangerous reagent, it must be handled with tweezers, since in contact with the skin it causes burns (phosphor bombs are used in the manufacture). White phosphorus is an insulator. Glows in the dark in air due to the transformation of P 2 O 3 on its surface into P 2 O5, more stable.

Red phosphorus has a cubic structure, black is orthorhombic, and violet is monoclinic. In liquid state (MP: 44.1 ºC) it smokes in the air with release of heat and formation of P2O5. It dissolves in carbon disulfide (CS 2 ) and phosphorous trichloride (PCl3) and is insoluble in water. It is extremely reactive and a very strong reducing agent: its reactions with sulfur and halogens are very violent. Above 700 ° C the P2 form appears. It is very poisonous: 50 mg is a lethal dose, and chronic ingestion of small amounts produces bone necrosis.

When white phosphorus is exposed to sunlight or heated to 250 ° C it becomes the red amorphous variety, which is not phosphorescent in air. It is not so dangerous since it is insoluble and does not burn spontaneously, it only does so above 260ºC, but it must be handled with care as it turns white and emits fumes of phosphorus oxides (which are very toxic) when heated . It is considerably less reactive unless it is faced with strong oxidants, such as potassium chlorate (KClO3), since it forms explosive mixtures: it is used (together with P4S3) in the manufacture of safety matches (mixed with KClO3 or other strong oxidants, explodes at the slightest supply of energy, such as friction), pyrotechnics, pesticides, incendiary bombs, smoke bombs, tracer bullets, etc. Violet phosphor (red-violet color) is not an important form. It has a layered structure. It is not poisonous.

Black phosphorus is the most thermodynamically stable form at room temperature; however, the transformation speeds of the other black shapes are very slow. It has a dark gray color with a metallic luster. It is flaky like graphite and, like graphite, conducts current and heat. It has a warped layered structure formed by fused hexagonal rings. It is obtained from the white variety at very high pressures and from the red variety at normal pressure and with catalysts and crystal seeding. Phosphorus (especially white and red) is used mainly in the manufacture of phosphoric acid and phosphates and polyphosphates (detergents).

Also in the production of steels, phosphor bronze (92.5% Cu, 7% Sn and 0.5% P) and other products: semiconductor doping.

Most important copies

Phosphorous hydride or phosphine (PH3) is an extremely poisonous colorless gas and is used in semiconductor doping and cereal fumigation. Phosphorous pentaoxide has a dimeric structure in solid and liquid state. There are at least four solid and two liquid modifications. It is hygroscopic and in air it converts into phosphoric acid. It is used as a drying agent.

Among the phosphorus sulfides, P4S3, which constitutes the incendiary mass of matches, and P4S10, which is used to obtain lubricants, as an insecticide and sulfur agent of organic combinations, are of interest.

Orthophosphoric or phosphoric acid is a medium strength acid. It is used in the manufacture of superphosphates (fertilizers), medicines and as an acidifier.

Natural phosphates are very insoluble in water; to increase their solubility they are treated with sulfuric acid: Calcium phosphate (apatite and phosphorite) treated with sulfuric acid gives rise to superphosphate (calcium dihydrogen phosphate and gypsum). Treated with phosphoric acid produces double superphosphate (hydrogen and calcium dihydrogen phosphate). The use of these superphosphates, with a P2O5 content of the order of 70-75%, has acquired great importance in agricultural production. This has increased the demand and production of phosphates. Phosphates are used in the production of specialty glasses, such as those used in sodium lamps.

Bone ash, composed of calcium phosphate, has been used to make porcelain and produce monocalcium phosphate, which is used in baking yeast powders. Trisodium Phosphate is a cleaning agent, to soften water and to prevent the formation of boiler scabs and corrosion of boiler pipes and tubes. Phosphorus is an essential component of bones and teeth; also of cellular protoplasm and nervous tissue. Phosphodiester bonds serve to store energy for cellular processes. Man needs a daily intake of 1 g in the form of phosphorous combinations.

Phosphorus Compounds

About three-quarters of total phosphorus (in all its chemical forms) is used in the United States as fertilizers. Other important applications are as detergent fillers, supplemental nutrients in animal feed, water softeners, food and drug additives, coating agents in metal surface treatment, metallurgical additives, plasticizers, insecticides, and petroleum product additives.

Of almost 200 different mineral phosphates, only one, fluoropatite, Ca5F (PO4) 3, is extracted essentially from large secondary deposits originating in the bones of animals and found at the bottom of prehistoric seas, and from guanos deposited on rocks. ancient. Research into the chemistry of phosphorus indicates that there may be as many phosphorus-based compounds as there are carbon-based ones. In organic chemistry it is customary to group various chemical compounds into families called homologous series.

This can also be done in the chemistry of phosphorus compounds, although many families are incomplete. The best known family of these compounds is the group of phosphate chains. Phosphate salts consist of cations, such as sodium, along with chains of anions, such as (PnO3n + 1) (n + 2) -, which can have 1 to 1,000,000 phosphorus atoms per anion.

Phosphates are based on phosphorous atoms surrounded in a tetrahedral arrangement by oxygen atoms, the smallest member of the family being the simple anion PO3-4 (the orthophosphate ion). The phosphate chain family is based on alternating rows of phosphorous and oxygen atoms in which each phosphorous atom remains in the center of a tetrahedron of four oxygen atoms. There is also a closely related family of cyclic phosphates.

An interesting structural feature of many of the known phosphorus compounds is the formation of cage-like structures. Examples of these molecules are white phosphorus, P4, and one of the phosphorous pentoxides, P 4 O 10 . Network-like structures are common; for example, black phosphorous crystals in which the atoms are bonded to each other.

In most of its compounds, phosphorus is chemically bonded to four immediate atoms. There are a large number of compounds in which one of the four atoms is absent and a pair of unshared electrons is in its place.

There are also a few compounds with five or six atoms attached to phosphorus; they are very reactive and tend to be unstable. During the 1960s and 1970s, many organic phosphorus compounds were prepared. Most of these chemical structures include three or four atoms bonded to phosphorus, but there are also structures with two, five or six atoms bonded to each phosphorous atom.

Most of the phosphorus used commercially is in the form of phosphates. Most phosphate fertilizers consist of highly impure calcium diacid orthophosphate or calcium acid otphosphate, Ca (H2PO4) 2 and CaHPO4. These phosphates are salts of orthophosphoric acid. The phosphorus compound of greatest biological importance is adenosine triphosphate (ATP), which is an ester of the salt, sodium tripolyphosphate, widely used in detergents and water softeners. Almost all reactions in metabolism and photosynthesis require the hydrolysis of this tripolyphosphate to its pyrophosphate derivative, called adenosine diphosphate (ADP).

Health effects

Phosphorus can be found in the environment most commonly as phosphate. Phosphates are important substances in the human body because they are part of the DNA material and have a part in the distribution of energy. Phosphates can be found commonly in plants. Humans have changed the natural supply of phosphorus radically by adding phosphate-rich manure. Phosphate was also added to a number of foods, such as cheeses, sauces, and ham. Too much phosphate can cause health problems, such as kidney damage and osteoporosis. Decreased phosphate can also occur. These are caused by extensive use of medicines. Too little phosphate can cause health problems.

Phosphorus in its pure form has a white color. White phosphorus is the most dangerous form of phosphorus that is known. When white phosphorus occurs in nature it can be a serious hazard to our health. White phosphorus is extremely poisonous and in many cases exposure to it will be fatal. In most cases, people who die from white phosphorus have been from accidentally swallowing rat poison. Before people die from exposure to white phosphorus they often experience nausea, stomach convulsions, and fainting. The white phosphorus can cause skin burns, damage the liver, heart and kidneys.

Environmental Effects of Phosphorus

White phosphorus: White phosphorus is in the environment when it is used in industries to make other chemicals and when the military uses it as ammunition. Through wastewater discharges, white phosphorus ends up in surface waters near the factories where it is used.

White phosphorus is probably not scattered, because it reacts with oxygen quite quickly. When phosphorus ends up in the air through the tailpipes it will usually end up reacting with oxygen instantly to become less dangerous particles. But in deep soils and at the bottom of rivers and lakes, phosphorus can remain for thousands of years and longer.

Phosphates: Phosphates have many effects on organisms. The effects are mainly consequences of the emissions of large amounts of phosphates into the environment due to mining and crops. During water purification, phosphates are often not removed properly, so they can spread over long distances when they are on the surface of the water.

Due to the constant addition of phosphates by humans and exceeding natural concentrations, the phosphorus cycle is strongly interrupted. Increasing the concentration of phosphorus in surface waters increases the growth of phosphorus-dependent organisms, such as algae. These organisms use large amounts of oxygen and prevent sunlight from entering the water. This makes the water unsuitable for the life of other organisms. The phenomenon is commonly known as eutrophication.

Phosphorus cycle

The proportion of phosphorus in living matter is relatively small, the role it plays is vital. It is a component of nucleic acids like DNA, many intermediates in photosynthesis and cellular respiration are combined with phosphorus, and phosphorus atoms provide the basis for the formation of the high-energy bonds of ATP, it is It is also found in the bones and teeth of animals, including humans.

The largest reserve of phosphorus is in the earth’s crust and in marine rock deposits.

Phosphorus cycle

Other cycles:Sulfur cycle * Nitrogen cycle

Carbon cycle * Oxygen cycle

Phosphorus is released from rocks and into the soil, where it is used by plants to perform their vital functions. Animals get phosphorus by feeding on plants or other animals they have ingested. In the bacterial decomposition of corpses, phosphorus is released in the form of orthophosphates (PO 4 H 2 ) that can be used directly by green plants, forming organic phosphate (plant biomass), the rain can transport this phosphate to the aquifers. or the oceans.

The phosphorus cycle differs from that of carbon, nitrogen, and sulfur in one main respect. Phosphorus does not form volatile compounds that allow it to pass from the oceans to the atmosphere and from there return to the mainland. Once at sea, there are only two mechanisms for the recycling of phosphorus from the ocean to terrestrial ecosystems. One is through seabirds that pick up phosphorus that passes through marine food chains and can return it to the mainland in their droppings. In addition to the activity of these animals, there is the possibility of the geological uplift of sediments from the ocean towards the mainland, a process measured in thousands of years.


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