Aluminium fluoride

Aside from anhydrous , several hydrates are known. With the formula , these compounds include monohydrate (x = 1), two polymorphs of the trihydrate (x = 3), a hexahydrate (x = 6), and a nonahydrate (x = 9). The majority of aluminium fluoride is produced by treating alumina with hydrogen fluoride at 700 °C: Hexafluorosilicic acid may also be used make aluminium fluoride. : Alternatively, it is manufactured by thermal decomposition of ammonium hexafluoroaluminate. For small scale laboratory preparations, can also be prepared by treating aluminium hydroxide or aluminium with hydrogen fluoride. Aluminium fluoride trihydrate is found in nature as the rare mineral rosenbergite. The anhydrous form appears as the relatively recently (as of 2020) recognized mineral óskarssonite. A related, exceedingly rare mineral, is zharchikhite, . ==Structure==

According to X-ray crystallography, anhydrous adopts the rhenium trioxide motif, featuring distorted octahedra. Each fluoride is connected to two Al centers. Because of its three-dimensional polymeric structure, has a high melting point. The other trihalides of aluminium in the solid state differ, Aluminium chloride| has a layer structure and aluminium bromide| and aluminium iodide|, are molecular dimers. Also they have low melting points and evaporate readily to give dimers. In the gas phase aluminium fluoride exists as trigonal molecules of D3h symmetry. The Al–F bond lengths of this gaseous molecule are 163 pm. ==Applications==

Aluminium fluoride is an important additive for the production of aluminium by electrolysis. The observation that aluminium fluoride can bind to and activate heterotrimeric G proteins has proven to be useful for the study of G protein activation in vivo, for the elucidation of three-dimensional structures of several GTPases, and for understanding the biochemical mechanism of GTP hydrolysis, including the role of GTPase-activating proteins. Niche uses Together with zirconium fluoride, aluminium fluoride is an ingredient for the production of fluoroaluminate glasses. It is also used to inhibit fermentation. Like magnesium fluoride it is used as a low-index optical thin film, particularly when far UV transparency is required. Its deposition by physical vapor deposition, particularly by evaporation, is favorable. ==Safety==

The reported oral animal lethal dose (LD50) of aluminium fluoride is 100 mg/kg. Repeated or prolonged inhalation exposure may cause asthma, and may have effects on the bone and nervous system, resulting in bone alterations (fluorosis), and nervous system impairment. Many of the neurotoxic effects of fluoride are due to the formation of aluminium fluoride complexes, which mimic the chemical structure of a phosphate and influence the activity of ATP phosphohydrolases and phospholipase D. Only micromolar concentrations of aluminium are needed to form aluminium fluoride. Human exposure to aluminium fluoride can occur in an industrial setting, such as emissions from aluminium reduction processes, or when a person ingests both a fluoride source (e.g., fluoride in drinking water or residue of fluoride-based pesticides) and an aluminium source; sources of human exposure to aluminium include drinking water, tea, food residues, infant formula, aluminium-containing antacids or medications, deodorants, cosmetics, and glassware. Data on the potential neurotoxic effects of chronic exposure to the aluminium species existing in water are limited. ==See also==