Calcium metal is a British chemist David and the Swedish chemist 柏齐利乌斯 obtained in 1809. Calcium is a silvery white metal, than lithium, sodium, potassium, the hard, heavy; melting at 815 ℃. Chemical properties of calcium metal is very lively. In air, calcium will soon be oxidized, covered with a layer oxide film. When heated, calcium will burn, emitting a beautiful brick red light. The role of calcium and cold water slowly, heated in hot water, a chemical reaction occurs, releasing hydrogen (lithium, sodium, potassium, even in cold water, also violent chemical reaction). Calcium is also very easy with a halogen, sulfur, nitrogen compounds.
Use of calcium:
Currently in the steel industry, metal calcium (calcium alloy) are mainly used for processing into metal calcium tablets, then made into pure calcium calcium and iron wire or cable, and ultimately for steel refining, its role is desulfurization, oxygen, increase the flow of molten steel, and promote the rapid inclusions in molten steel float, generally used for the production of high quality steel; used as a dehydrating agent, manufactured ethanol; in the oil industry, as a desulfurization agent in the metallurgical industry, sulfur phenylephrine or go with it. However, the calcium compound, but has a very wide range of applications, especially in the construction industry.
Still talking about it from the marble. Marble is a very expensive building materials; because of the rich in the name of Dali County, also produces other places, but also called "marble." Marble is a limestone. The chemical composition of limestone calcium carbonate. Limestone is mostly gray, hard, very brittle. In nature, often a large area composed of limestone formations are composed. Limestone is used to repair reservoirs, paving, building bridges. Such as Henan Linxian famous "canal", is to use locally produced limestone Toru into.
Limestone in the lime kiln, and coke combustion are mixed together to produce quicklime (Figure 40). The chemical composition of quicklime CaO. Lime is a white stone, it is very interesting, an intense water will occur chemical reaction into a white powder - slaked lime, and release a lot of heat (Figure 41). On the building site, and you can often see people adding water to quicklime. At this time, if put inside eggs, enough to put it cooked. The chemical composition of slaked lime is calcium hydroxide can be dissolved in water. Lime is calcium hydroxide solution, lime brush on the wall, at first, not how white, after a while children, but it will be more white. This is an interesting cycle: slaked lime and the role of carbon dioxide in the air, once again became a calcium carbonate; However, people in the lime kiln, but it is of limestone (calcium carbonate) to firing lime. When burned, the carbon dioxide released limestone into calcium oxide.
Calcium sulfate, calcium is also important compounds, the common name of gypsum, slightly soluble in water. In industry, people use various models made of plaster to cast gold, silver, aluminum, magnesium, copper, and alloys of these non-ferrous metals. Gypsum is also used to manufacture a large variety of plaster elephant. However, natural gypsum is not dense snow-white solid, as the wax appearance touches, which is an aqueous crystalline. Gypsum burning before becoming mature plaster.
Natural water, such as rivers, lakes, river, often contain some soluble calcium compounds such as calcium bicarbonate. This water is called hard water. Hard water to bring a lot of trouble, and use it to boil water, the original calcium bicarbonate dissolved in water heating will be converted into insoluble calcium carbonate, precipitated into boiler scale. Factory boiler scale boiler if too thick, not only a waste of fuel, or even cause an explosion due to uneven heating; using it clothes, soap and calcium bicarbonate chemical reaction, to precipitate out calcium stearate, wasted soaps. In order to overcome these disadvantages of hard water, people often take water softening, such as adding soda (sodium carbonate), you can make into a calcium carbonate precipitate out calcium bicarbonate, filtered out. The method also makes some with boiling water softening.
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