Phosphate minerals, origin

The iron formed in a blast furnace, called pig iron, contains impurities that make the metal brittle. These include phosphorus and silicon from silicate and phosphate minerals that contaminated the original ore, as well as carbon and sulfur from the coke. This iron is refined in a converter furnace. Here, a stream of O2 gas blows through molten impure iron. Oxygen reacts with the nonmetal impurities, converting them to oxides. As in the blast furnace, CaO is added to convert Si02 into liquid calcium silicate, in which the other oxides dissolve. The molten iron is analyzed at intervals until its impurities have been reduced to satisfactory levels. Then the liquid metal, now in the form called steel, is poured from the converter and allowed to solidify. 

In the sequence of presentation originally given, the last compound to be considered was phosphates. An outstanding example in this context is the chlorination of phosphate minerals of rare earths. The chlorination of monazite, for example, may be represented by the reactions ... 

The impurities in pig iron, the iron formed in a blast furnace, that make it brittle include four elements phosphorus and silicon, two elements that came from the silicate and phosphate minerals that contaminated the original ore, and carbon and sulfur that came from the coke. 

As is true today, most phosphate in the primordial crust must have been sequestered in nearly insoluble calcium phosphates and carbonates or in basalts, and only dissolved monomeric phosphate was produced by weathering. [201] However, the volatile polyphosphate P4O10 is known to be a component of volcanic gases. [205] This material originates from the polymerization of phosphate minerals in mag-... 

The content of phosphorus in the Earth s crust is about 0.1%, however P plays a very important role in the biosphere. This element was originated as a melted-out component of the crustal matter. Its further evolutionary history in the biosphere was complicated and in many details poorly understood. In basalts the P concentration is 0.14% and in granites twice as low. There are about 200 phosphorus-containing minerals. However, due to low crustal abundance of this element, they are not rockforming materials. The overall phosphorus mass in the granite layer of the lithosphere is 63300 X 10 tons. The most abundant phosphate mineral is apatite, which accounts for more than 95% of all P in the Earth s crust. The basic composition of this mineral is listed in Table 18. 

The overall natural and artificial cycles involving phosphorus may be represented approximately as in Figure 2.6. Unlike other essential life elements H, C, N, O, no appreciable amounts of gaseous phosphorus compounds are involved, and the P cycles are restricted to the lithosphere and the hydrosphere. Rainwater contains 0.001 ppm P. Originally, it can be supposed that sufficient phosphorus became available for life processes through the slow solubilisation of phosphate mineral deposits. The resulting distribution of the element on land and in the seas then enabled the initiation and development of life to take place. Subsequent death and decay of these organisms ensured a return of phosphorus to the system. 

Phosphorus occurs in various phosphate minerals, the most important belonging to the apatite family, which originate from the compressed remains of ancient organisms. Apatite has the general formula Ca5(P04)3X, where X can be OH" (hydroxyapatite), F (fluorapatite) or Cl" (chlorapatite). 

The solvent action of mineral oil base stocks can cause skin problems and prolonged exposure may have been the origin of a few skin cancers . The use of additives that might be in any way harmful to health, e.g. ortho-tricresyl phosphate (anti-wear) and sodium mercaptobenzothiazole (anticorrosion) has been discontinued where skin contact is likely. 

Phosphorite A hydrogenous mineral that forms in surficial sediments underlying surface waters of high biological productivity. It is composed primarily of calcium phosphate that is biogenic in origin. 

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