Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine.
Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, granular, or massive, depending on the method of formation.
Crystals of calcite, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
Coke is a fuel with few impurities and a high carbon content, usually made from coal. It is the carbonaceous material derived from destructive distillation of low-ash. Cokes made from coal are grey and porous, while coke can be formed naturally, the commonly used form is man-made. The form known as coke, or pet coke, is derived from oil refinery coker units or other cracking processes. Coke is used in preparation of producer gas which is a mixture of carbon monoxide, producer gas is produced by passing air over red-hot coke. Coke is used to water gas. Historical sources dating to the 4th century describe the production of coke in ancient China, the Chinese first used coke for heating and cooking no than the ninth century. By the first decades of the century, Chinese ironworkers in the Yellow River valley began to fuel their furnaces with coke. In 1589 a patent was granted to Thomas Proctor and William Peterson for making iron and steel and melting lead with earth-coal, sea-coal, the patent contains a distinct allusion to the preparation of coal by cooking.
In 1590 a patent was granted to the Dean of York to purify pit-coal, in 1620 a patent was granted to a company composed of William St. John, Robert Follensbee and other knights, mentioning the use of coke in smelting ores and manufacturing metals. In 1627 a patent was granted to Sir John Hacket and Octavius de Strada for a method of rendering sea-coal and pit-coal as useful as charcoal for burning in houses, without offense by smell or smoke. In 1603 Hugh Plat suggested that coal might be charred in an analogous to the way charcoal is produced from wood. In 1709 Abraham Darby I established a coke-fired blast furnace to produce cast iron, cokes superior crushing strength allowed blast furnaces to become taller and larger. The ensuing availability of iron was one of the factors leading to the Industrial Revolution. Before this time, iron-making used large quantities of charcoal, produced by burning wood, in the late 18th century, brick beehive ovens were developed, which allowed more control over the burning process.
In 1768 John Wilkinson built a more practical oven for converting coal into coke, with greater skill in the firing and quenching of the heaps, yields were increased from about 33 per cent to 65 per cent by the middle of the 19th century. The Scottish iron industry expanded rapidly in the second quarter of the 19th century. In 1802 a battery of beehives was set up near Sheffield, by 1870, there were 14,000 beehive ovens in operation on the West Durham coalfields, capable of producing 4.2 million tons of coke
Jack Lynch Tunnel
The Jack Lynch Tunnel is an immersed tube tunnel and an integral part of the N40 southern ring road of Cork in Ireland. It is named after former Taoiseach, Jack Lynch, a native of Cork and it takes the road under the River Lee. North of the tunnel, the ring-road joins the M8 motorway to Dublin and N8 road to the city centre, the tunnel was completed in May 1999, and carried nearly 40,000 vehicles per day as of 2005. Traffic in 2015 is 63,000 vehicles a day up from 59,000 in 2013, the tunnel has two cells, each with two traffic lanes and two footpaths, and a central bore for use in an emergency only. Pedestrians and cyclists are expressly forbidden from using the tunnel, Corks suburbs were expanding and traffic was rising as car ownership increased, but the city centres street plan, laid out in the late Middle Ages, was ill equipped to cope. The engineers reasoned that the congestion in the city centre and its radial routes was quickly reaching intolerable levels. They pushed through Corks LUTS – Land Use and Transportation Study – plan, to lay down a twenty five-year plan for the growth of transport.
The transportation proposals combined construction of elements of a road, a downstream crossing. The location and type of crossing was not established by the LUTS plan, no road development in Ireland prior to that date had required such a large investment, and therefore the plan met with some opposition on the grounds of cost. A team led by J. D. Shinkwin, Director of DeLeuw Chadwick O’hEocha, the first stage of the report established that the crossing should be located in Dunkettle, rather than at Tivoli, closer to the city centre. The second stage endorsed an immersed tube tunnel as the preferred scheme versus a bridge, the primary reasons were that a tunnel would have a lower construction cost relative to its utility, shorter approach gradients, lower environmental impact and no effect on shipping once built. The other alternative considered by the Steering Committee was an opening span bridge, while this solution would avoid the ramp problem of a high-level bridge, traffic would halt whenever the bridge had to open.
Shipping volumes into Corks port area was rising steadily in the 1980s, a sworn Public Inquiry into Cork Corporations application for a bridge order providing for a two-lane tunnel was held in October 1985. The required inspectors report was submitted in January 1987 to the Minister of the Environment, at that point, the report remained on the ministers desk for some time. In this context the operational programme for roads … includes the proposal for the commencement of the crossing during the programme period 1989–1993. In 1989, the government recommended a further feasibility study to consider the need for a crossing, the study confirmed the findings of the original Feasibility Study. A further Public Inquiry was held, with hearings in July and December 1990, in 1992, the Minister approved a Bridge Order for a four lane immersed tube tunnel. In the intervening time, the Irish government had established the National Roads Authority to advance the long term development of the national roads network
Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical and decorative usage in, for example, window panes and optoelectronics. The most familiar, and historically the oldest, types of glass are silicate glasses based on the chemical compound silica, the primary constituent of sand. The term glass, in usage, is often used to refer only to this type of material. Many applications of silicate glasses derive from their optical transparency, giving rise to their use as window panes. Glass can be coloured by adding metallic salts, and can be painted and printed with vitreous enamels and these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures, because glass can be formed or moulded into any shape, it has been traditionally used for vessels, vases, bottles and drinking glasses.
In its most solid forms it has used for paperweights, marbles. Some objects historically were so commonly made of glass that they are simply called by the name of the material, such as drinking glasses. Porcelains and many polymer thermoplastics familiar from everyday use are glasses and these sorts of glasses can be made of quite different kinds of materials than silica, metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass, silica is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, fused quartz is a glass made from chemically-pure SiO2. It has excellent resistance to shock, being able to survive immersion in water while red hot. However, its high melting-temperature and viscosity make it difficult to work with, other substances are added to simplify processing. One is sodium carbonate, which lowers the transition temperature.
The soda makes the glass water-soluble, which is undesirable, so lime, some magnesium oxide. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass, soda-lime glasses account for about 90% of manufactured glass. Most common glass contains other ingredients to change its properties, lead glass or flint glass is more brilliant because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium increases the refractive index, iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs UV wavelengths
Singapore, officially the Republic of Singapore, sometimes referred to as the Lion City or the Little Red Dot, is a sovereign city-state in Southeast Asia. It lies one degree north of the equator, at the tip of peninsular Malaysia. Singapores territory consists of one island along with 62 other islets. Since independence, extensive land reclamation has increased its size by 23%. During the Second World War, Singapore was occupied by Japan, after early years of turbulence, and despite lacking natural resources and a hinterland, the nation developed rapidly as an Asian Tiger economy, based on external trade and its workforce. Singapore is a global commerce and transport hub, the country has been identified as a tax haven. Singapore ranks 5th internationally and first in Asia on the UN Human Development Index and it is ranked highly in education, life expectancy, quality of life, personal safety, and housing, but does not fare well on the Democracy index. Although income inequality is high, 90% of homes are owner-occupied, 38% of Singapores 5.6 million residents are permanent residents and other foreign nationals.
There are four languages on the island, Mandarin, Tamil. English is its language, most Singaporeans are bilingual. Singapore is a multiparty parliamentary republic, with a Westminster system of unicameral parliamentary government. The Peoples Action Party has won every election since self-government in 1959, however, it is unlikely that lions ever lived on the island, Sang Nila Utama, the Srivijayan prince said to have founded and named the island Singapura, perhaps saw a Malayan tiger. There are however other suggestions for the origin of the name, the central island has been called Pulau Ujong as far back as the third century CE, literally island at the end in Malay. In 1299, according to the Malay Annals, the Kingdom of Singapura was founded on the island by Sang Nila Utama and these Indianized Kingdoms, a term coined by George Cœdès were characterized by surprising resilience, political integrity and administrative stability. In 1613, Portuguese raiders burned down the settlement, which by was part of the Johor Sultanate.
The wider maritime region and much trade was under Dutch control for the following period, in 1824 the entire island, as well as the Temenggong, became a British possession after a further treaty with the Sultan. In 1826, Singapore became part of the Straits Settlements, under the jurisdiction of British India, prior to Raffles arrival, there were only about a thousand people living on the island, mostly indigenous Malays along with a handful of Chinese. By 1860 the population had swelled to over 80,000, many of these early immigrants came to work on the pepper and gambier plantations
Wollastonite is a calcium inosilicate mineral that may contain small amounts of iron and manganese substituting for calcium. It forms when impure limestone or dolostone is subjected to temperature and pressure sometimes in the presence of silica-bearing fluids as in skarns or contact metamorphic rocks. Associated minerals include garnets, diopside, epidote, plagioclase feldspar, pyroxene and it is named after the English chemist and mineralogist William Hyde Wollaston. Some of the properties that make wollastonite so useful are its high brightness and whiteness, low moisture and oil absorption, Wollastonite is used primarily in ceramics, friction products, paint filler, and plastics. World production data for wollastonite is not available for many countries, estimated world production of crude wollastonite ore was in the range of 530,000 to 550,000 tonnes in 2010. World reserves of wollastonite were estimated to exceed 90 million tonnes, many large deposits have not been surveyed yet. In 2010, the producers were China, United States, Mexico.
Finland has long been a major European supplier of wollastonite, in the United States, wollastonite is mined in Willsboro, New York and Gouverneur, New York. Deposits have been mined commercially in North Western Mexico, in plastics, wollastonite improves tensile and flexural strength, reduces resin consumption, and improves thermal and dimensional stability at elevated temperatures. Surface treatments are used to improve the adhesion between the wollastonite and the polymers to which it is added, in some industries, it is used in different percentages of impurities, such as its use as a fabricator of mineral wool insulation, or as an ornamental building material. Ceramic applications probably account for 30% to 40% of wollastonite sales worldwide, followed by polymers with 30% to 35% of sales, the remaining sales were for construction, friction products, and metallurgical applications. The price of raw wollastonite varied in 2008 between US$80 and US$500 per tonne depending on the country and size and shape of the powder particles, in ceramics, wollastonite competes with carbonates, feldspar and silica as a source of calcium and silicon.
Its use in ceramics depends on the formulation of the ceramic body, in a pure CaSiO3, each component forms nearly half of the mineral by weight,48. 3% of CaO and 51. 7% of SiO2. In some cases, small amounts of iron, and manganese, Wollastonite can form a series of solid solutions in the system CaSiO3-FeSiO3, or hydrothermal synthesis of phases in the system MnSiO3-CaSiO3. Wollastonite crystallizes triclinically in space group P1 with the constants a =7.94 Å, b =7.32 Å, c =7.07 Å, α =90, 03°, β =95, 37°, γ =103, 43°. Wollastonite was once classed structurally among the group, because both of these groups have a ratio of Si, O =1,3. In 1931, Warren and Biscoe showed that the structure of wollastonite differs from minerals of the pyroxene group. It has been shown that the chains are more kinked than those of pyroxene group
In engineering, abutment refers to the substructure at the ends of a bridge span or dam whereon the structures superstructure rests or contacts. Multi-span bridges require piers to support ends of spans unsupported by abutments, Dam abutments are generally either side of a valley or gorge but may be artificial in order to support arch dams such as Kurobe Dam in Japan. The term may refer to the structure supporting one side of an arch. Also the impost or abacus of a column in classical architecture may serve as an abutment to an arch, the word derives from the verb abut, meaning to touch by means of a mutual border. An abutment may be used for the following, To transfer loads from a superstructure to its foundation elements, to resist and/or transfer self weight, lateral loads and wind loads. To support one end of an approach. Every time I drive down the road I wanna’ jerk the wheel into a Goddamn bridge abutment, in the film The Big Lebowski The Dudes car was stolen and located by the police.
The officer who found it told The Dude It was discovered last night in Van Nuys lodged against an abutment, to which The Dude responded Oh man, lodged where. Ohio Department of Transportation Fixed Bridge Abutments
In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time and they are used in both extractive metallurgy and metal joining. Some of the earliest known fluxes were carbonate of soda, charcoal, borax, lead sulfide, iron ore was used as a flux in the smelting of copper. As cleaning agents, fluxes facilitate soldering and welding by removing oxidation from the metals to be joined, the slag is a liquid mixture of ash and other impurities. This reduction of slag viscosity with temperature, increasing the flow of slag in smelting, is the origin of the word flux in metallurgy. Fluxes are used in foundries for removing impurities from molten nonferrous metals such as aluminium, in high-temperature metal joining processes, the primary purpose of flux is to prevent oxidation of the base and filler materials. Tin-lead solder attaches very well to copper, but poorly to the oxides of copper. Flux is a substance which is inert at room temperature.
Additionally, flux allows solder to flow easily on the piece rather than forming beads as it would otherwise. In some applications molten flux serves as a heat transfer medium, fluxes for soft soldering are typically of organic nature, though inorganic fluxes, usually based on halogenides and/or acids, are used in non-electronics applications. Fluxes for brazing operate at higher temperatures and are therefore mostly inorganic. Organic fluxes typically consist of four components, Activators - chemicals disrupting/dissolving the metal oxides. Their role is to expose unoxidized, easily wettable metal surface and aid soldering by other means, highly active fluxes contain chemicals that are corrosive at room temperature. The compounds used include metal halides, hydrochloric acid, phosphoric acid, Salts of mineral acids with amines are used as aggressive activators. Aggressive fluxes typically facilitate corrosion, require careful removal, and are unsuitable for finer work, Activators for fluxes for soldering and brazing aluminium often contain fluorides.
Milder activators begin to react with oxides only at elevated temperature, typical compounds used are carboxylic acids and sometimes amino acids. Some milder fluxes contain halides or organohalides, vehicles - high-temperature tolerant chemicals in the form of non-volatile liquids or solids with suitable melting point, they are generally liquid at soldering temperatures. Solid vehicles tend to be based on natural or modified rosin or natural or synthetic resins, water-soluble organic fluxes tend to contain vehicles based on high-boiling polyols - glycols, diethylene glycol and higher polyglycols, polyglycol-based surfactants and glycerol
Types of concrete
There are many types of concrete, designed to suit a variety or purposes coupled with a range of compositions and performance characteristics. Modern concrete mix designs can be complex, the choice of a concrete mix depends on the need of the project both in terms of strength and appearance and in relation to local legislation and building codes. The design begins by determining the requirements of the concrete and these requirements take into consideration the weather conditions that the concrete will be exposed to in service, and the required design strength. The compressive strength of a concrete is determined by taking standard molded, standard-cured cylinder samples, many factors need to be taken into account, from the cost of the various additives and aggregates, to the trade offs between the slump for easy mixing and placement and ultimate performance. A mix is designed using cement and fine aggregates, water. The method of mixing will be specified, as well as conditions that it may be used in and this allows a user of the concrete to be confident that the structure will perform properly.
Various types of concrete have been developed for specialist application and have known by these names. Concrete mixes can be designed using software programs, such software provides the user an opportunity to select their preferred method of mix design and enter the material data to arrive at proper mix designs. Concrete has been used since ancient times, Regular Roman concrete for example was made from volcanic ash, and hydrated lime. Roman concrete was superior to other concrete recipes used by other nations, besides volcanic ash for making regular Roman concrete, brick dust can be utilized. Besides regular Roman concrete, the Romans invented hydraulic concrete, the ingredients in any particular mix depends on the nature of the application. Regular concrete can typically withstand a pressure from about 10 MPa to 40 MPa, many types of pre-mixed concrete are available which include powdered cement mixed with an aggregate, needing only water. Typically, a batch of concrete can be made by using 1 part Portland cement,2 parts dry sand,3 parts dry stone, the parts are in terms of weight – not volume.
For example, 1-cubic-foot of concrete would be made using 22 lb cement,10 lb water,41 lb dry sand,70 lb dry stone and this would make 1-cubic-foot of concrete and would weigh about 143 lb. The sand should be mortar or brick sand and the stone should be washed if possible, organic materials should be removed from the sand and stone to ensure the highest strength. High-strength concrete has a strength greater than 40 MPa. In the UK, BS EN 206-1 defines High strength concrete as concrete with a compressive strength class higher than C50/60, high-strength concrete is made by lowering the water-cement ratio to 0.35 or lower. Often silica fume is added to prevent the formation of calcium hydroxide crystals in the cement matrix
Calcium carbonate is a chemical compound with the formula CaCO3. It is a substance found in rocks as the minerals calcite and aragonite and is the main component of pearls and the shells of marine organisms, snails. Calcium carbonate is the ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a supplement or as an antacid. Calcium carbonate shares the properties of other carbonates. CaCO3 + CO2 + H2O → Ca2 This reaction is important in the erosion of rock, forming caverns. An unusual form of calcium carbonate is the hexahydrate, ikaite is stable only below 6 °C. The vast majority of calcium used in industry is extracted by mining or quarrying. Pure calcium carbonate, can be produced from a quarried source. Alternatively, calcium carbonate is prepared from calcium oxide, other forms can be prepared, the denser, orthorhombic λ-CaCO3 and μ-CaCO3, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures above 85 °C, calcite contains calcium atoms coordinated by 6 oxygen atoms, in aragonite they are coordinated by 9 oxygen atoms.
The vaterite structure is not fully understood, magnesium carbonate MgCO3 has the calcite structure, whereas strontium and barium carbonate adopt the aragonite structure, reflecting their larger ionic radii. Calcite and vaterite are pure calcium carbonate minerals, industrially important source rocks which are predominantly calcium carbonate include limestone, chalk and travertine. Eggshells, snail shells and most seashells are predominantly calcium carbonate, oyster shells have enjoyed recent recognition as a source of dietary calcium, but are a practical industrial source. While not practical as a source, dark green vegetables such as broccoli. Beyond Earth, strong evidence suggests the presence of Calcium carbonate on Mars, signs of Calcium Carbonate have been detected at more than one location. This provides some evidence for the past presence of liquid water, Carbonate is found frequently in geologic settings and constitute an enormous carbon reservoir. Calcium carbonate occurs as aragonite and dolomite, the carbonate minerals form the rock types, chalk, travertine and others
Portland cement is the most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar and most non-speciality grout. It was developed from other types of lime in England in the mid 19th century. It is a fine powder produced by heating materials in a kiln to form what is called clinker, grinding the clinker, and adding small amounts of other materials. Several types of Portland cement are available, with the most common being called ordinary Portland cement which is grey in color, Portland cement is caustic, so it can cause chemical burns. The powder can cause irritation or, with exposure, lung cancer and can contain some hazardous components such as crystalline silica. Concrete produced from Portland cement is one of the most versatile construction materials available in the world, Portland cement was developed from natural cements made in Britain beginning in the middle of the 18th century. Its name is derived from its similarity to Portland stone, a type of building stone quarried on the Isle of Portland in Dorset, England.
In the late 18th century, Roman cement was developed and patented in 1796 by James Parker, Roman cement quickly became popular, in 1811 James Frost produced a cement he called British cement. James Frost is reported to have erected a manufactory for making of an artificial cement in 1826, in 1843, Aspdins son William improved their cement, which was initially called Patent Portland cement, although he had no patent. In 1818, French engineer Louis Vicat invented a hydraulic lime considered the principal forerunner of Portland cement. Edgar Dobbs of Southwark patented a cement of this kind in 1811, Portland cement was used by Joseph Aspdin in his cement patent in 1824 because of the cements resemblance to Portland stone. The name Portland cement is recorded in a directory published in 1823 being associated with a William Lockwood, a Dave Stewart, Aspdins cement was nothing like modern Portland cement but was a first step in the development of modern Portland cement, called a proto-Portland cement.
William Aspdin had left his fathers company and in his cement manufacturing apparently accidentally produced calcium silicates in the 1840s, in 1848, William Aspdin further improved his cement, in 1853, he moved to Germany, where he was involved in cement making. William Aspdin made what could be called meso-Portland cement, isaac Charles Johnson further refined the production of meso-Portland cement and claimed to be the real father of Portland cement. John Grant of the Metropolitan Board of Works in 1859 set out requirements for cement to be used in the London sewer project and this became a specification for Portland cement. The Hoffman endless kiln which gave control over combustion was tested in 1860. This cement was made at the Portland Cementfabrik Stern at Stettin and it is thought that the first modern Portland cement was made there. The Association of German Cement Manufacturers issued a standard on Portland cement in 1878, by the early 20th century American-made Portland cement had displaced most of the imported Portland cement
Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron.
Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, muscles, bone marrow, blood proteins, ferritin and transport in plasma.
The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have been studied extensively