Aluminum fluoride refers to inorganic compounds with the formula AlF 3 x H 2 O. They are all colorless solids. Anhydrous AlF 3 is used in the production of aluminum metal. Many occur in the form of minerals.
| virtue | |
|---|---|
| chemical formula | ALF 3 |
| molar mass | 83.977 g/mol (anhydrous) 101.992 g/mol (monohydrate) 138.023 (trihydrate) |
| appearance | white, crystalline solid odorless |
| density | 3.10 g/cm3 ( anhydrous) 2.17 g/cm3 ( monohydrate) 1.914 g/cm3 ( trihydrate ) |
| Melting point | 1,290 °C (2,350 °F; 1,560 K)(anhydrous) (sublime) |
| Solubility in water | 5.6 g/l (0 °C) 6.7 g/l (20 °C) 17.2 g/l (100 °C) |
| magnetic susceptibility (χ) | −13.4 × 10 −6 cm 3 /mol |
| refractive index ( nd ) | 1.3767 (visible limit) |
event and production
In addition to the anhydrous AlF 3 , several hydrates are known. With the formula AlF 3 X H 2 O, these compounds include a monohydrate ( X = 1), two polymorphs of the trihydrate ( X = 3), a hexahydrate ( X = 6) and a nonhydrate ( X = 9). [10]
The majority of aluminum fluoride is produced by treating alumina with hydrogen fluoride at 700 °C: [4] fluorosilicic acid can also be used to make aluminum fluoride.
H 2 Cif 6 + Al 2 O 3 + 3 H 2 O → 2 Alf 3 + Co 2 + 4 H 2 O
Alternatively, it is produced by the thermal decomposition of ammonium hexafluoroaluminate. [12] For small-scale laboratory preparation, AlF 3 can also be prepared by treating aluminums hydroxide or aluminums metal with hydrogen fluoride.
Aluminum fluoride trihydrate is a rare mineral found in nature as rosenbergite. The anhydrous form appears as the relatively recently (as of 2020) recognized mineral óskarssonite. [13] [14] A related, extremely rare mineral, zarchikhite, is Al(OH) 2F .
structure
According to X-ray crystallography, anhydrous AlF adopts the rhenium trioxide motif, with distorted AlF 6 octahedra . Each fluoride is attached to two Al centers. Due to its three-dimensional polymer structure, AlF 3 has a high melting point. Other trihalides of aluminum differ from those in the solid state, AlCl 3 having a single layer structure and AlBr 3 and AlI 3 being molecular dimers. Also they have low melting points and easily evaporate to give dimers. aluminum fluoride D3H in the gas phaseThe symmetry of triangular molecules exists in the form. The Al-F bond length of this gaseous molecule is 163 pm.
Application
Aluminum fluoride is an important additive for the production of aluminum by electrolysis. [4] Together with cryolite, it lowers the melting point below 1000 °C and increases the conductivity of the solution. It is in this molten salt that aluminum oxide is dissolved and then electrolyzed to give the bulk Al metal. [12]
Aluminum fluoride complexes are used in biology to study the mechanistic aspects of phosphoryl transfer reactions, which are of fundamental importance to cells, as most of the reactions involved in phosphoric acid anhydride metabolism, growth, and differentiation, such as ATP and GTP, are controlled. control. [19] The observation that aluminum fluoride can bind to and activate heterotrimeric G proteins has led to the study of G protein activation in vivo, to the elucidation of the three-dimensional structures of many GTPases, and to understanding the biochemical mechanisms. has proved useful. GTP hydrolysis, including the role of GTPase-activated proteins. [20]
Got used
Along with zirconium fluoride, aluminum fluoride is an ingredient for the production of fluoroaluminate glass.
It is also used to stop fermentation.
Like magnesium fluoride it is used as a low-index optical thin film, especially when far UV transparency is required. Its deposition by physical vapor deposition, especially by evaporation, is favourable.
Security
The reported oral animal lethal dose (LD50) of aluminum fluoride is 0.1 g/kg. [21] Frequent or prolonged inhalation can lead to asthma, and can affect the bone and nervous system, resulting in bone changes (fluorosis), and nervous system damage.
Many of the neurotoxic effects of fluoride are due to the formation of aluminum fluoride complexes, which mimic the chemical structure of a phosphate and affect the activity of ATP phosphohydrolases and phospholipase D. Making aluminum fluoride requires only micromolar concentrations of aluminum.
Human exposure to aluminum fluoride can occur in an industrial setting, such as emissions from aluminum reduction processes, [24] or when a person is exposed to a fluoride source (eg, fluoride in drinking water or fluoride-based pesticide residues) and a Aluminum swallows both. Source; Sources of human exposure to aluminum include drinking water, tea, food residues, infant formula, aluminum-containing antacids or medicines, deodorants, cosmetics and glassware. [23] Fluoridation chemicals may also contain aluminum fluoride. [25] There is limited data on the potential neurotoxic effects of long-term exposure to aluminum species present in water.
