Atomic number 15
Atomic mass 30,9738 g.mol -1
Density 1,82 g/ml at 20°C
Melting point 44,2 °C
Boiling point 280 °C
Discovered by Hennig Brandt in 1669
Phosphorous is a multivalent nonmetal of the nitrogen group. It is found in nature in several allotropic forms, and is an essential element for the life of organisms.
There are several forms of phosphorous, called white, red and black phosphorous, although the their colours are more likely to be slightly different. White phosphorous is the one manufactured industrial; it glows in the dark, is spontaneously flammable when exposed to air and is deadly poison. Red phosphorous can vary in colour from orange to purple, due to slight variations in its chemical structure. The third form, black phosphorous, is made under high pressure, looks like graphite and, like graphite, has the ability to conduct electricity.
Concentrated phosphoric acids are used in fertilizers for agriculture and farm production. Phosphates are used for special glasses, sodium lamps, in steel production, in military applications (incendiary bombs, smoke screenings etc.), and in other applications as: pyrotechnics, pesticides, toothpaste, detergents.
In the natural world phosphorous is never encountered in its pure form, but only as phosphates, which consists of a phosphorous atom bonded to four oxygen atoms. This can exists as the negatively charged phosphate ion (PO43-), which is how it occurs in minerals, or as organophosphates in which there are organic molecules attached to one, two or three of the oxygen atoms.
The amount of phosphorous that is naturally present in food varies considerably but can be as high as 370 mg/100 g in liver, or can be low, as in vegetable oils. Foods rich in phosphorous include tuna, salmon, sardines, liver, turkey, chicken, eggs and cheese (200 g/100 g).
There are many phosphate minerals, the most abundant being forms of apatite. Fluoroapatite provides the most extensively mined deposits. The chief mining areas are Russia, USA, Morocco, Tunisia, Togo and Nauru. World production is 153 million tones per year. There are concerns over how long these phosphorous deposits will last. In case of depletion there could be a serious problem for the worlds food production since phosphorus is such an essential ingredient in fertilizers.
In the oceans, the concentration of phosphates is very low, particularly at the surface. The reason lies partly within the insolubility of aluminum and calcium phosphates, but in any case in the oceans phosphate is quickly used up and falls into the deep as organic debris. There can be more phosphate in rivers and lakes, resulting in excessive algae growth . For further details go to environmental effects of phosphorous .
Phosphorus can be found in the environment most commonly as phosphates. Phosphates are important substances in the human body, because they are a part of DNA materials and they take part in energy distribution. Phosphates can also be found commonly in plants.
Phosphate is a dietary requirement, the recommended intake is 800 mg/day, a normal diet provides between 1000 and 2000 mg/day, depending on the extent to which phosphate rich foods are consumed.
Humans have changed the natural phosphate supply radically by addition of phosphate-rich manures to the soil and by the use of phosphate-containing detergents. Phosphates were also added to a number of foodstuffs, such as cheese, sausages and hams.
Too much phosphate can cause health problems, such as kidney damage and osteoporosis. Phosphate shortages can also occur. These are caused by extensive use of medicine. Too little phosphate can cause health problems.
Phosphorus in its pure form has a white colour. White phosphorus is the most dangerous form of phosphorus that is known to us. When white phosphorus occurs in nature this can be a serious danger to our health. White phosphorus is extremely poisonous and in many cases exposure to it will be fatal.
In most cases people that died of white phosphorus exposure had been accidentally swallowing rat poison. Before people die from white phosphorus exposure they often experience nausea, stomach cramps and drowsiness.
White phosphorus can cause skin burns. While burning, white phosphorus may cause damage to the liver, the heart or the kidneys.
White phosphorus enters the environment when industries use it to make other chemicals and when the army uses it as ammunition. Through discharge of wastewater white phosphorus ends up in surface waters near the factories that use it.
White phosphorus is not likely to spread, because it reacts with oxygen fairly quickly. When phosphorus ends up in air through exhausts it will usually react with oxygen right away to be converted into less harmful particles. However, when phosphorus particles are in air they may have a protective coating that prevents chemical reactions.
In water, white phosphorus is not reacting with other particles that quickly and as a result it will accumulate in the bodies of aquatic organisms. In soil phosphorus will remain for several days before it is converted into less harmful substances. But in deep soils and the bottom of rivers and lakes phosphorus may remain for a thousand years or so.
Phosphates have many effects upon organisms. The effects are mainly consequences of emissions of large quantities of phosphate into the environment due to mining and cultivating. During water purification phosphates are often not removed properly, so that they can spread over large distances when found in surface waters.
Due to the constant addition of phosphates by humans and the exceeding of the natural concentrations, the phosphor cycle is strongly disrupted.
The increasing phosphor concentrations in surface waters raise the growth of phosphate-dependent organisms, such as algae and duckweed. These organisms use great amounts of oxygen and prevent sunlight from entering the water. This makes the water fairly unliveable for other organisms. This phenomenon is commonly known as eutrophication .