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Ammonium Fluoride

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]

Ammonium Fluoride Formula

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

Ammonium Fluoride Crystals

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

Ammonium Fluoride Structure

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

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