Phosphorus: A Macromineral
21. May 2013
1. Introduction 1.1. History Phosphorus is the first element to be discovered having an historical register. In 1669, a German merchant called Henning Brand obtained elementary phosphorus through the distillation of urine, writing a letter to Leibniz reporting its discovery. It is quite probable that, in the 12th century, Arabian alchemists have obtained the element using this process. However, the credit is given to Brand. The name of phosphorus has a Greek origin meaning "it possesses brilliance" due to its property of shining in the darkness when exposed to the air. Phosphorus was the 13th element to be discovered. For this reason, and also due to its use in explosives, poisons and nerve agents, it is sometimes referred to as "the Devil's element". Further investigations by Brand's contemporary researchers revealed that the addition of sand or coal to urine helped the freeing of phosphorus. About one century after its original work, Brand discovered that phosphorus is an important constituent of the bones, introducing a new method of industrial production of phosphorus. The reaction of the bones with nitric or sulfuric acid produces phosphoric acid that, when heated up with coal, produces elementary phosphorus. This was the first method of phosphorus commercial production. At the end of the 19th century, James Readman developed the first process for the production of the element with an electrical furnace. In spite of many design and operation improvements of electrical furnaces, the basics of Readman's method to obtain elementary phosphorus remains in present technology. Due to its important role in biological processes, phosphorus is one of the most dispersed elements in Nature. It does not occur as a free element, but is common to find in the phosphate form in about 0, 10% of earth's crust. It is the 11th more abundant element occurring in almost all volcanic and sedimentary rocks. Phosphorus occurs in almost all the volcanic rocks, having been present in the volcanic eruptions during the period of Earth formation. The erosion, by water, of the deposits of volcanic phosphates, and later assimilation by prehistoric plants, introduced the phosphorus in the biological mechanisms. The phosphorus can be found in almost 190 different minerals, but only the apatite series has an important role as phosphorus source. This series is represented by the following formula for a unitary cell Ca10(PO4)6 (F, Cl ou OH)2.Some phosphorus compounds glow in the dark or emit light in response to absorbing radiation and are used in fluorescent light bulbs and television sets. Calcium phosphate (phosphate rock), mostly mined in Florida and North Africa, can be heated to 1,200–1,500 °C with sand, which is mostly SiO2, and coke (impure carbon) to produce vaporized P4. The product is subsequently condensed into a white powder under water to prevent oxidation by air. Even under water, white phosphorus is slowly converted to the more stable red phosphorus allotrope. The chemical equation for this process when starting with fluoroapatite, a common phosphate mineral, is: 4 Ca5(PO4)3F + 18 SiO2 + 30 C → 3 P4 + 30 CO + 18 CaSiO3 + 2 CaF2 The worst incident in recent times was an environmental one in 1968 when the sea became contaminated due to spillages and/or inadequately treated sewage from a white phosphorus plant at Placentia Bay, Newfoundland. Another process by which elemental phosphorus is extracted includes applying at high temperatures 1500 °C 2 Ca3(PO4)2 + 6 SiO2 + 10 C → 6CaSiO3 + 10 CO + P4
1.2. Driving Question My driving question is “how chemical properties of elements relate to their role as essential dietary minerals?” - Vitamins and minerals are essential nutrients because they perform hundreds of roles in the body.