Calcium fluoride is an inorganic compound with the chemical formula CaFtwoIt is colorless crystal or white powder.Insoluble in water, slightly soluble inInorganic acid, and thermalconcentrated sulfuric acidAction generationhydrofluoric acid。Generally, calcium fluoride is prepared by the reaction of calcium carbonate with hydrofluoric acid or by repeatedly treating fluorite powder with concentrated hydrochloric acid or hydrofluoric acid.The calcium fluoride minerals in nature arefluoriteOr fluorspar, often gray, yellow, green, purple and other colors, sometimes colorless, transparent, glassy, brittle, with significant fluorescence.Very pure fluorspar is used to make special lenses.Fluorite is mainly used as a flux for smelting metals;When the drinking water contains 1-1.5 ppm calcium fluoride, it can prevent and cure dental diseases.[1]
Crystal structure: GenusIsometric, in the form of a cube, octahedron, or dodecahedron.Colorless crystal or white powder, containing impurities in natural ores, slightly green or purple.Glow when heated.Density 3.18g/cmthree, melting point 1402 ℃, boiling point 2500 ℃, refractive index 1.434.Low toxicity.Extremely insoluble in water.Soluble in hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid and ammonium salt solution, insoluble in acetone.When dissolved in aluminum salt and iron salt solution, it forms a complex and reacts with hot concentrated sulfuric acid to generate hydrofluoric acid.Calcium fluoride reacts with concentrated sulfuric acid in a lead container to produce hydrogen fluoride.It can form eutectic with various metal oxides.
preparation
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takecalcium carbonateorcalcium hydroxideDissolve the solution with hydrofluoric acid, concentrate the solution, or add fluoride ions to the calcium salt solution to obtain colloidal precipitation of calcium fluoride, which can be obtained through refining.Calcium carbonate andhydrofluoric acidThe calcium fluoride is prepared by repeatedly treating fluorite powder with concentrated hydrochloric acid and hydrofluoric acid.
existence
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The calcium fluoride mineral in nature is fluorite or fluorite, which is gray, yellow, green, purple and other colors due to different impurities. Sometimes it is colorless, transparent, glassy, brittle, with a relative density of 3.01~3.25, and has a significant fluorescence phenomenon.The synthetic pure calcium fluoride crystal is also colorless and transparent.Very pure fluorspar is used to make special lenses.Fluorite is mainly used as a flux for smelting metals.
purpose
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executive summary
The use of calcium fluoride is very extensive. With the progress of science and technology, the application prospect is more and more broad.It is mainly used in metallurgy, chemical industry and building materials, followed by light industry, optics, sculpture and national defense industry.Therefore, according to the use requirements, China's fluorite mineral products mainly have four series of varieties, namely fluorite block ore, fluorite (fluorite) concentrate, fluorite powder ore and optical and carving fluorite.
metallurgical industry
Fluorite can reduce the melting point of refractory materials, promote slag flow, and make slag and metal well separateddesulphurization、dephosphorizationIt can enhance the calcinability and tensile strength of metal.Therefore, it acts asFluxIt is widely used in iron and steel smelting, ferroalloy production, iron melting process and non-ferrous metal smelting.
chemical industry
Another important use of fluorite is the production of hydrofluoric acid.Hydrofluoric acid is produced by the reaction of acid grade fluorite (fluorite concentrate) with sulfuric acid in the heating furnace or tank. It is divided into anhydrous hydrofluoric acid and aqueous hydrofluoric acid. They are colorless liquids, volatile, with strong pungent smell and strong corrosiveness.It is the key raw material for the production of various organic and inorganic fluorides and fluorine elements.
Building materials industry
Fluorite is also widely used in glass, ceramics, cement and other building materials industries, and its consumption ranks second in China.
In the glass industry, fluorite is used as a fluxSunscreenWhen added, it can promote the melting of glass raw materials;In cement production, fluorite is used asMineralizerJoin.Fluorite can reduce the sintering temperature of furnace charge, reduce fuel consumption, and enhance the liquid viscosity of clinker during sinteringTricalcium silicateFormation of;In the ceramic industry, fluorite is mainly used as porcelain glaze, which can play a role in assisting color and melting in the production process of porcelain glaze;Fluorite is also used in enamel industry and cast stone production.
Other uses
With the improvement of people's living standards, the demand for ornaments and handicrafts is increasing.Fluorite has dense structure, bright and diverse colors, and is valued by people as the raw material of craft carving.
national standard
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Calcium Fluoride (GB/T 27804-2011) came into force on June 1, 2012.
