Ammonium fluoride
| |||
 | |||
 | |||
| Names | |||
|---|---|---|---|
| IUPAC name
Ammonium fluoride | |||
| Other names
Neutral ammonium fluoride | |||
| Identifiers | |||
12125-01-8  | |||
| ChemSpider | 23806 | ||
| EC Number | 235-185-9 | ||
| Jmol 3D model | Interactive image | ||
| RTECS number | BQ6300000 | ||
| UN number | 2505 | ||
| |||
| |||
| Properties | |||
| NH4F | |||
| Molar mass | 37.037 g/mol | ||
| Appearance | White crystalline solid hygroscopic | ||
| Density | 1.009 g/cm3 | ||
| Melting point | 100 °C (212 °F; 373 K) (decomposes) | ||
| 45.3 g/100 ml (25 °C) | |||
| Solubility | slightly soluble in alcohol, insoluble in liquid ammonia | ||
| Structure | |||
| Wurtzite structure (hexagonal) | |||
| Hazards | |||
| Safety data sheet | ICSC 1223 | ||
| EU classification (DSD) |
Toxic (T) | ||
| R-phrases | R23/24/25 | ||
| S-phrases | (S1/2), S26, S45 | ||
| NFPA 704 | |||
| Flash point | Non-flammable | ||
| Related compounds | |||
| Other anions |
Ammonium chloride Ammonium bromide Ammonium iodide | ||
| Other cations |
Sodium fluoride Potassium fluoride | ||
| Related compounds |
Ammonium bifluoride | ||
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
verify (what is  ?) | |||
| Infobox references | |||
Ammonium fluoride is the inorganic compound with the formula NH4F. It crystallizes as small colourless prisms, having a sharp saline taste, and is exceedingly soluble in water.
Crystal structure
Ammonium fluoride adopts the wurtzite crystal structure, in which both the ammonium cations and the fluoride anions are stacked in ABABAB... layers, each being tetrahedrally surrounded by four of the other. There are NH...F hydrogen bonds between the anions and cations.[1] This structure is very similar to ice, and ammonium fluoride is the only substance which can form mixed crystals with water.[2]
Reactions
On passing hydrogen fluoride gas (in excess) through the salt, ammonium fluoride absorbs the gas to form the addition compound ammonium bifluoride. The reaction occurring is:
- NH4F + HF → NH4HF2
It sublimes when heated—a property common among ammonium salts. In the sublimation, the salt decomposes to ammonia and hydrogen fluoride, and the two gases can recombine to give ammonium fluoride, i.e. the reaction is reversible:
- [NH4]F ⇌ NH3 + HF
Uses
This substance is commonly called "commercial ammonium fluoride". The word "neutral" is sometimes added to "ammonium fluoride" to represent the neutral salt—[NH4]F vs. the "acid salt" (NH4HF2). The acid salt is usually used in preference to the neutral salt in the etching of glass and related silicates. This property is shared among all soluble fluorides. For this reason it cannot be handled in glass test tubes or apparatus during laboratory work.
It is also used for preserving wood, as a mothproofing agent, in printing and dying textiles, and as an antiseptic in breweries.[3]
References
- ↑ A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
- ↑ Brill, R.; Zaromb, S. "Mixed Crystals of Ice and Ammonium Fluoride". Nature 173 (4398): 316–317. doi:10.1038/173316a0.
- ↑ Aigueperse, Jean; Paul Mollard; Didier Devilliers; Marius Chemla; Robert Faron; Renée Romano; Jean Pierre Cuer (2005). "Fluorine Compounds, Inorganic". In Ullmann. Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307.