Ammonium bifluoride
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Names | |||
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IUPAC name Ammonium bifluoride | |||
Other names
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Identifiers | |||
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3D model (JSmol) |
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ChemSpider |
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ECHA InfoCard | 100.014.252 | ||
EC Number |
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PubChem CID |
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UNII |
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UN number | 1727 | ||
CompTox Dashboard (EPA) |
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InChI
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Properties | |||
Chemical formula | [NH4][HF2] | ||
Molar mass | 57.044 g·mol−1 | ||
Appearance | Colourless crystals | ||
Density | 1.50 g cm−3 | ||
Melting point | 126 °C (259 °F; 399 K) | ||
Boiling point | 240 °C (464 °F; 513 K)(decomposes) | ||
Solubility in water | 63g/(100 ml) (20 °C) | ||
Solubility in alcohol | slightly soluble | ||
Refractive index (nD) | 1.390 | ||
Structure | |||
Crystal structure | Cubic, related to the CsCl structure | ||
[NH4]+ cation: tetrahedral [HF2]− anion: linear | |||
Hazards | |||
GHS labelling: | |||
[1] | |||
H301, H314[1] | |||
P280, P301+P310, P305+P351+P338, P310[1] | |||
NFPA 704 (fire diamond) | 3 0 0 | ||
Related compounds | |||
Other cations | potassium bifluoride | ||
Related compounds | ammonium fluoride | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references |
Ammonium bifluoride is the inorganic compound with the formula [NH4][HF2] or [NH4]F·HF. It is produced from ammonia and hydrogen fluoride. This colourless salt is a glass-etchant and an intermediate in a once-contemplated route to hydrofluoric acid.
Structure
Ammonium bifluoride, as its name indicates, contains an ammonium cation ([NH4]+), and a bifluoride or hydrogen(difluoride) anion ([HF2]−). The centrosymmetric triatomic bifluoride anion features the strongest known hydrogen bond, with a F−H length of 114 pm.[2] and a bond energy greater than 155 kJ/mol.[3]
In solid [NH4][HF2], each ammonium cation is surrounded by four fluoride centers in a tetrahedron, with hydrogen-fluorine hydrogen bonds present between the hydrogen atoms of the ammonium ion and the fluorine atoms.[4][5] Solutions contain tetrahedral [NH4]+ cations and linear [HF2]− anions.
Production and applications
Ammonium bifluoride is a component of some etchants. It attacks silica component of glass:
- SiO2 + 4 [NH4][HF2] → SiF4 + 4 [NH4]F + 2 H2O
Potassium bifluoride is a related more commonly used etchant.
Ammonium bifluoride has been considered as an intermediate in the production of hydrofluoric acid from hexafluorosilicic acid. Thus, hexafluorosilicic acid is hydrolyzed to give ammonium fluoride, which thermally decomposes to give the bifluoride:
- H2[SiF6] + 6 NH3 + 2 H2O → SiO2 + 6 [NH4]F
- 2 [NH4]F → NH3 + [NH4][HF2]
The resulting ammonium bifluoride is converted to sodium bifluoride, which thermally decomposes to release HF.[6]
Ammonium bifluoride is also used as an additive in tin-nickel plating processes as the fluoride ion acts as a complexing agent with the tin, allowing for greater control over the resulting composition and finish.
Toxicity
Ammonium bifluoride is toxic to consume and a skin corrosion agent. Upon exposure to skin, rinsing with water followed by a treatment of calcium gluconate is required.[1] In water, ammonium bifluoride exists in chemical equilibrium with hydrofluoric acid and heating releases hydrogen fluoride gas.[7] Consequently, there is an equivalent toxicological risk as is present with hydrofluoric acid, and the same safety precautions apply.[8][7]
Ammonium bifluoride is used in some automotive wheel cleaning products. Many injuries have resulted in users not being aware of the risks posed by the products.[9] Ammonium bifluoride based products are often considered a safer alternative to hydrofluoric acid, yet still pose clear risks to the handler.[8] Ammonium bifluoride, ammonium fluoride, and hydrofluoric acid have been described as "too dangerous for any use in a car wash environment" by Professional Car Washing and Detailing magazine,[10] advice that accords with a 2015 report from the U.S. Centers for Disease Control and Prevention.[11]
References
- ^ a b c d Sigma-Aldrich Co., Ammonium bifluoride. Retrieved on 2013-07-20.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ Emsley, J. (1980) Very Strong Hydrogen Bonds, Chemical Society Reviews, 9, 91–124. doi:10.1039/CS9800900091
- ^ McDonald, T. R. R. (1960). "The electron-density distribution in ammonium bifluoride". Acta Crystallogr. 13 (2): 113–124. Bibcode:1960AcCry..13..113M. doi:10.1107/S0365110X60000261.
- ^ "ICSD Entry: 14140". Cambridge Structural Database: Access Structures. Cambridge Crystallographic Data Centre. Retrieved 2022-06-25.
- ^ Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307. ISBN 3527306730.
- ^ a b National Industrial Chemicals Notification and Assessment Scheme (April 17, 2020). "Bifluorides: Human health tier II assessment" (PDF). Department of Health (Australia). Retrieved February 8, 2023.
- ^ a b Genuino, Homer C.; Opembe, Naftali N.; Njagi, Eric C.; McClain, Skye; Suib, Steven L. (2012). "A review of hydrofluoric acid and its use in the car wash industry". Journal of Industrial and Engineering Chemistry. 18 (5): 1529–1539. doi:10.1016/j.jiec.2012.03.001. ISSN 1226-086X.
- ^ Gormley, James (May 29, 2001). "The truth about ammonium bifluoride". Professional Car Washing and Detailing. Archived from the original on 2001-05-29.
- ^ Cook, Ryan (October 9, 2013). "The Five Factors of Clean: Chemistry, Part 1". Professional Car Washing and Detailing. Retrieved February 8, 2023.
- ^ Woodie, Maria (December 1, 2015). "OSHA gives employees the right to know". Professional Car Washing and Detailing. Retrieved February 8, 2023.
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HF | He | |||||||||||||||||
LiF | BeF2 | BF BF3 B2F4 | CF4 CxFy | NF3 N2F4 | OF OF2 O2F2 O2F | F− | Ne | |||||||||||
NaF | MgF2 | AlF AlF3 | SiF4 | P2F4 PF3 PF5 | S2F2 SF2 S2F4 SF4 S2F10 SF6 | ClF ClF3 ClF5 | HArF ArF2 | |||||||||||
KF | CaF2 | ScF3 | TiF3 TiF4 | VF2 VF3 VF4 VF5 | CrF2 CrF3 CrF4 CrF5 CrF6 | MnF2 MnF3 MnF4 | FeF2 FeF3 | CoF2 CoF3 | NiF2 NiF3 | CuF CuF2 | ZnF2 | GaF3 | GeF4 | AsF3 AsF5 | SeF4 SeF6 | BrF BrF3 BrF5 | KrF2 KrF4 KrF6 | |
RbF | SrF2 | YF3 | ZrF4 | NbF4 NbF5 | MoF4 MoF5 MoF6 | TcF6 | RuF3 RuF4 RuF5 RuF6 | RhF3 RhF5 RhF6 | PdF2 Pd[PdF6] PdF4 PdF6 | AgF AgF2 AgF3 Ag2F | CdF2 | InF3 | SnF2 SnF4 | SbF3 SbF5 | TeF4 TeF6 | IF IF3 IF5 IF7 | XeF2 XeF4 XeF6 XeF8 | |
CsF | BaF2 | * | LuF3 | HfF4 | TaF5 | WF4 WF6 | ReF6 ReF7 | OsF4 OsF5 OsF6 OsF 7 OsF8 | IrF3 IrF5 IrF6 | PtF2 Pt[PtF6] PtF4 PtF5 PtF6 | AuF AuF3 Au2F10 AuF5·F2 | HgF2 Hg2F2 HgF4 | TlF TlF3 | PbF2 PbF4 | BiF3 BiF5 | PoF4 PoF6 | At | RnF2 RnF6 |
Fr | RaF2 | ** | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
↓ | ||||||||||||||||||
* | LaF3 | CeF3 CeF4 | PrF3 PrF4 | NdF3 | PmF3 | SmF2 SmF3 | EuF2 EuF3 | GdF3 | TbF3 TbF4 | DyF3 | HoF3 | ErF3 | TmF2 TmF3 | YbF2 YbF3 | ||||
** | AcF3 | ThF4 | PaF4 PaF5 | UF3 UF4 UF5 UF6 | NpF3 NpF4 NpF5 NpF6 | PuF3 PuF4 PuF5 PuF6 | AmF3 AmF4 AmF6 | CmF3 | Bk | Cf | Es | Fm | Md | No |
- AgPF6
- KAsF6
- LiAsF6
- NaAsF6
- HPF6
- HSbF6
- NH4PF6
- LiSbF6
- KPF6
- KSbF6
- LiPF6
- NaPF6
- NaSbF6
- TlPF6
- Cs2AlF5
- Li3AlF6
- K3AlF6
- Na3AlF6
and pseudohalogenides
- BaSiF6
- BaGeF6
- (NH4)2SiF6
- Na2[SiF6]
- K2[SiF6]
- Li2GeF6
- Li2SiF6
- CBrF3
- CBr2F2
- CBr3F
- CClF3
- CCl2F2
- CCl3F
- CF2O
- CF3I
- CHF3
- CH2F2
- CH3F
- C2Cl3F3
- C2H3F
- C6H5F
- C7H5F3
- C15F33N
- C3H5F
- C6H11F
lanthanide, actinide, ammonium
- VOF3
- CrOF4
- CrF2O2
- NH4F
- (NH4)2ZrF6
- CsXeF7
- Li2SnF6
- Li2TiF6
- Li2ZrF6
- K2TiF6
- Rb2TiF6
- Na2TiF6
- Na2ZrF6
- K2NbF7
- K2TaF7
- K2ZrF6
- UO2F2
- FNO
- FNO2
- FNO3
- KHF2
- NaHF2
- NH4HF2
and iodosyl
- F2OS
- F3OP
- PSF3
- IOF3
- IO3F
- IOF5
- IO2F
- IO2F3