Ammonium fluoride is a crystalline, noncombustible inorganic compound represented by the chemical formula NH₄F or FH₄N ^{[1, 2]}. It is a fluoride salt with ammonium as the counterion and is corrosive to cement, glass, and most metals, including aluminum ^{[1, 2]}.

Ammonium Fluoride Identification
CAS Number	12125-01-8 [1]
PubChem CID	25516 [1]
ChemSpider ID	23806 [3]
UN Number	2505 [1]
UNII	4QT928IM0A [1]
EC Number	235-185-9 [1]
RTECS Number	BQ6300000 [1]
InChI Key	LDDQLRUQCUTJBB-UHFFFAOYSA-N [1]

How is Ammonium Fluoride Prepared

It is synthesized by the addition of ammonia gas to cold hydrofluoric acid at a temperature of about 10 °C represented by the reaction ^[4]:

NH₃ + HF → NH₄F

It can be prepared by using silicon tetrafluoride gas (SiF₄) and high purity ammonia (NH₃) as reactants, which is given in the following equations ^[4]:

3SiF₄ + 2H₂O → 2H₂SiF₆ + SiO₂

H₂SiF₆ + 2NH₃ → (NH₄)₂SiF₆

(NH₄)₂SiF₆ + 4NH₃ + 2H₂O → SiO₂ + 6NH₄F

Reactions with Other Compounds

Ammonium Fluoride and Water

When NH₄F reacts with water, it produces hydrofluoric acid and ammonium hydroxide, as represented by the following equation ^[2]:

NH₄F + H₂O → NH₄OH + HF

Calcium Nitrate and Ammonium Fluoride

Ammonium fluoride reacts with calcium nitrate to form calcium fluoride, dinitrogen oxide, and water:

Ca(NO₃)₂ + 2NH₄F → CaF₂ + 2N₂O + 4H₂O

Ammonium Fluoride and Iodine

When ammonium fluoride and iodine are used as reactants, they undergo a single displacement reaction to form ammonium iodide and fluorine:

NH₄F + I₂ → NH₄I₂ + F

Properties and Characteristics of Ammonium Fluoride

General Properties
Molar Mass/Molecular Weight	37.037 g/mol [1]
Physical Properties
Color and Appearance	White or colorless crystalline powder [1]
Melting Point	238 °C, 460.4 °F [1]
Boiling Point	N/A
Density	1.01 g cm-3, 1.32 at 77 °F [1]
pH	Aqueous NH4F is acidic [1]
State of matter at room temperature	Dry powder or liquid [1]
Solubility	Insoluble in liquid NH3, slightly soluble in alcohol [1]
Solubility in Water	83.5 g/100 g at 25 °C [1]
Magnetic Susceptibility (χ)	-23.0 X 10-6 cm3/mol
Atomic Properties
Crystal Structure	Hexagonal wurtzite

Uses

• For etching glass, polishing metal surfaces, extracting rare metals, and disinfection and preservation in the brewing industry ^[5]
• As masking agents, preservatives, and reagents for analysis ^[5]
• For wood preservation, complexometric titration of aluminum, spot analysis of zirconium, and glass engraving ^[5]

Is It Safe

NH₄F causes acute toxicity when it is swallowed, inhaled, or comes in contact with skin ^[1]. Its inhalation may result in irritation of the respiratory tract and ingestion of small quantities of soluble fluorides can also be fatal ^[1]. Its contact with skin causes burns, and exposure through eye contact can irritate the mucous membrane ^[1].

References
1. Ammonium Fluoride – Pubchem.ncbi.nlm.nih.gov
2. Ammonium Fluoride – Cameochemicals.noaa.gov
3. Ammonium Fluoride – Chemspider.com
4. Synthesis of Ammonium Fluoride: A Literature Review – Repository.up.ac.za
5. Ammonium Fluoride – Chemicalbook.com