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Aluminium fluoride is an important additive for the production of aluminium by electrolysis. [4] Together with cryolite, it lowers the melting point to below 1000 °C and increases the conductivity of the solution. It is into this molten salt that aluminium oxide is dissolved and then electrolyzed to give bulk Al metal. [12]
The Hall–Héroult process is the major industrial process for smelting aluminium.It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite and electrolyzing the molten salt bath, typically in a purpose-built cell.
The carbon–fluorine bond of the smaller molecules is formed in three principal ways: Fluorine replaces a halogen or hydrogen, or adds across a multiple bond. The direct reaction of hydrocarbons with fluorine gas can be dangerously reactive, so the temperature may need to be lowered even to −150 °C (−240 °F). [115] "
Reactions of elemental fluorine with metals require varying conditions. Alkali metals cause explosions and alkaline earth metals display vigorous activity in bulk; to prevent passivation from the formation of metal fluoride layers, most other metals such as aluminium and iron must be powdered, [ 21 ] and noble metals require pure fluorine gas ...
Aluminium: Solid Al 0 Aluminium chloride: Solid AlCl 3: −705.63 Aluminium oxide: Solid Al 2 O 3: −1675.5 Aluminium hydroxide: Solid Al(OH) 3: −1277 Aluminium sulphate: Solid Al 2 (SO 4) 3: −3440 Barium chloride: Solid BaCl 2: −858.6 Barium carbonate: Solid BaCO 3: −1216 Barium hydroxide: Solid Ba(OH) 2: −944.7 Barium oxide: Solid ...
The difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s). Pure cryolite itself melts at 1012 °C (1285 K), and it can dissolve the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis. Substantial energy is still ...
In physical chemistry and engineering, passivation is coating a material so that it becomes "passive", that is, less readily affected or corroded by the environment. . Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material, or allowed to build by spontaneous oxidation
The electrowinning of aluminium relies on the electrolysis of aluminium fluoride in molten cryolite. Several kilograms of HF are consumed per ton of Al produced. Other metal fluorides are produced using HF, including uranium tetrafluoride. [14] HF is the precursor to elemental fluorine, F 2, by electrolysis of a solution of HF and potassium ...
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