Ammonium hydrogen difluoride

Structural formula
General
Surname	Ammonium hydrogen difluoride
other names	Ammonium bifluoride; Ambi;
Molecular formula	NH 4 HF 2
Brief description	colorless solid
External identifiers / databases
EC number	215-676-4
ECHA InfoCard	100.014.252
PubChem	14935
ChemSpider	21241205
Wikidata	Q473546
properties
Molar mass	57.04 g · mol -1
Physical state	firmly
density	1.5 g cm −3
Melting point	124.6 ° C
boiling point	230 ° C (decomposition)
solubility	good in water (630 g l −1 at 20 ° C)
safety instructions
H and P phrases	H: 301-314
	P: 260-280-301 + 330 + 331 + 310-303 + 361 + 353-304 + 340 + 310-305 + 351 + 338
MAK	1 mg m −3
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Ammonium hydrogen difluoride is an acidic ammonium salt of hydrofluoric acid .

properties

Ammonium hydrogen difluoride forms colorless, easily deliquescent crystals that are easily soluble in water. It etches glass and is also used in industry for stain removal and in the petroleum industry to work through granite layers. The species attacking the silicon dioxide is the HF ₂^- anion. It is the active component of various etching mixtures for the selective etching of silicon dioxide layers in the semiconductor industry .

Reactions

When heated strongly, it breaks down into ammonia and hydrogen fluoride.

${\ displaystyle \ mathrm {NH_ {4} HF_ {2} (s) \ rightarrow NH_ {3} (g) +2 \ HF (g)}}$

synthesis

Ammonium hydrogen difluoride is prepared by reacting aqueous ammonia solution with hydrofluoric acid in a molar ratio of 1: 2 and then crystallizing from water.

${\ displaystyle \ mathrm {NH_ {3} (aq) + \ 2 \ HF (aq) \ rightarrow \ NH_ {4} HF_ {2} (aq)}}$

Precautions

Ammonium hydrogen difluoride is corrosive and toxic. Avoid contact with skin and eyes. Do not swallow.

disposal

Precipitate dissolved fluoride as calcium fluoride .

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Entry on ammonium hydrogen difluoride in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
↑ Entry on ammonium hydrogendifluoride in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
^ The Electrochemical Society: Cleaning Technology in Semiconductor Device Manufacturing. The Electrochemical Society, 2000, ISBN 978-1-566-77259-4 , p. 248 ( limited preview in Google book search).
^ Tadahiro Ohmi: Scientific Wet Process Technology for Innovative LSI / FPD Manufacturing. CRC Press, 2016, ISBN 978-1-420-02686-3 , p. 178 ( limited preview in Google book search).
↑ Alain Tressaud: Functionalized Inorganic Fluorides Synthesis, Characterization and Properties of Nanostructured Solids . John Wiley & Sons, 2010, ISBN 0-470-66075-9 , pp. 210 ( limited preview in Google Book search).

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Entry on ammonium hydrogen difluoride in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

[CLP_100.014.252-2] Entry on ammonium hydrogendifluoride in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[books--2cGOyJz7TEC-248-3] The Electrochemical Society: Cleaning Technology in Semiconductor Device Manufacturing. The Electrochemical Society, 2000, ISBN 978-1-566-77259-4 , p. 248 ( limited preview in Google book search).

[books-_u7KBQAAQBAJ-178-4] Tadahiro Ohmi: Scientific Wet Process Technology for Innovative LSI / FPD Manufacturing. CRC Press, 2016, ISBN 978-1-420-02686-3 , p. 178 ( limited preview in Google book search).

[Alain_Tressaud-5] Alain Tressaud: Functionalized Inorganic Fluorides Synthesis, Characterization and Properties of Nanostructured Solids . John Wiley & Sons, 2010, ISBN 0-470-66075-9 , pp. 210 ( limited preview in Google Book search).