Red phosphorus is one of the most common and widely used allotropes of the nonmetallic element, phosphorus. Find out its various uses through this ScienceStruck article
Did You Know?
The credit for discovering phosphorus is given to the German alchemist, Hennig Brand, who isolated this element from urine in 1669. Red phosphorus, on the other hand, was discovered in 1845 by an Austrian chemist, Anton von Schrötter
Phosphorus is a nonmetallic element with the symbol P. Its atomic number is 15, and it is a member of the nitrogen family. Phosphorus is commonly found in inorganic phosphate rocks. It is a highly reactive chemical element, and so it is usually not found in its elemental form.
Within the living cells, phosphorus is an important component of DNA and RNA, and also occurs as phospholipids that form the cell membrane. Phosphorus is a component of ATP or adenosine triphosphate, which is the major source of energy for the cellular reactions taking place within living cells. Phosphorus can be found in several forms or allotropes. Allotropes can be defined as the structurally different forms of an element. The white and red phosphorus are the most common allotropes of phosphorus.
What is Red Phosphorus?
It is one of the several allotropes of phosphorus. Red phosphorus is made up of four tetrahedrally grouped phosphorus atoms. It is a hard crystalline solid that is insoluble in water and carbon disulphide. It can be obtained by heating white phosphorus to 250ºC. It can also be obtained by simply exposing white phosphorus to sunlight. By heating red phosphorus to over 550ºC, we can obtain violet phosphorus.
As compared to white phosphorus, red phosphorus is not so dangerous. It is not poisonous and it does ignite spontaneously in the air, if temperature is kept below 250ºC. So, it is relatively stable and less reactive than white phosphorus. However, at some temperature ranges, it can change back to white phosphorus. Many times, frictional heating is also enough to convert red phosphorus to white phosphorus. When heated, red phosphorus can emit toxic fumes, which mainly contains phosphorus oxides.
Uses of Red Phosphorus
Being more stable and less reactive than white phosphorus, it has found several industrial and pharmaceutical uses. It is used in making the strike plate of matchboxes, while the match head is made with sodium chlorate or potassium chlorate. The friction produced when the match head makes contact with the strike plate generates heat. This causes a small amount of red phosphorus to change back to white phosphorus, which burns spontaneously in the air. As a result, the match head lights up.
Next to matchboxes, this allotrope of phosphorus can be found in fertilizers. Fertilizers made with red phosphorus are effective in promoting plant growth, proper root development, and flower and seed production. Plants fertilized with phosphorus-based fertilizers become resistant to diseases and pest invasion. This type of fertilizer can help plants synthesize proteins more effectively, which in turn, can ensure better growth and development.
Pesticides are meant for destroying or repelling pests. An infestation of pests can cause considerable damage to crops. Pesticides can help protect crops, and thus increase food production. Red phosphorus is one among many other chemicals used in pesticides. But nowadays, a lot of concern has been expressed regarding the safety of such chemical pesticides.
In the pharmaceutical sector, phosphorus is used in the synthesis of methamphetamine, which is a drug that can stimulate the central nervous system. To produce methamphetamine, red phosphorus is combined with elemental iodine, which results in the production of hydriodic acid (HI). The hydriodic acid is then used to convert ephedrine or pseudoephedrine to methamphetamine.
Methamphetamine is basically a psychoactive drug that can alter mood, and improve alertness and the level of energy by increasing the level of neurotransmitters, like dopamine, serotonin, and norepinephrine in the brain. Methamphetamine has a high potential for abuse, for which many laws and regulations have been enforced regarding its production and use.
Fireworks and Pyrotechnic Devices
Red phosphorus does not react spontaneously in the air, and so, it is much safer than white phosphorus. For this reason, red phosphorus is often used in commercial fireworks and other pyrotechnic devices, such as luminous projectiles. When we light a firework, the heat produced in the process converts red phosphorus to white phosphorus, which then ignites when exposed to air.
Both red and white phosphorus have found a place in smoke and obscurant devices, such as smoke bombs. In such devices, red phosphorus is mixed with magnesium or another initiator and a binder. A dense, white smoke is produced from burning phosphorus. Such a smoke screen is usually used to conceal the movements or location of military units.
Despite being a flammable material, red phosphorus can act as a flame retardant when added to plastics, rubber, and resins. Generally, a 5 to 10% solution of red phosphorus is added to plastics that are to be used in electronics, in order to reduce the risk of ignition.
A semiconductor is a material having electrical conductivity between a metal and an insulator. Its conductivity or electrical properties can be modified to a great extent by introducing some impurities into its crystal lattice. This process is known as doping, and phosphorus is one of the dopant elements used for this purpose. It is usually used for doping silicon.
A tracer bullet is a type of tracer ammunition that leaves a luminous or smoky trail so that the shooter can hit the target effectively by following the trail. A tracer projectile contains a pyrotechnic flare material, which is usually made of phosphorus or magnesium.
Red phosphorus is usually mixed with a binder to be used in flares. It basically helps ignite, as well as sustain the burning of flares, that can be used for signaling or illumination. Flares are largely used in an emergency for signaling purposes.
In addition to these, red phosphorus is used for manufacturing a few other products, such as rat and mice poison, and electroluminescent coatings. To sum up, red phosphorus is one of the most important allotropes of phosphorus, having numerous applications in the industrial sector.