artemov - 15-6-2020 at 23:30
I might be able to get a small amount of ammonium bifluoride and I'm thinking of converting it to the safer sodium fluoride (hopefully more stable as
well) for storage. I have no use for fluoride at the moment.
I have in mind using either NaOH (high solubility) or Na2CO3/NaHCO3 (lower solubility)
NH4HF2 + 2NaOH -> 2NaF + NH4OH + H2O
? NH4HF2 + 2NaHCO3 -> 2NaF + NH4HCO3 + CO2 + H2O
?? NH4HF2 + Na2CO3 -> ???
Not sure about the last 2 reactions ... I am also hoping no free ammonia will be released.
NaF has low solubility at 0 C compared to the ammonium salts, so I should be able to ppt out the NaF with some loss ...
Which would be a better method? Any comment or advice, with regards to safety as well? Cheers.
Boffis - 16-6-2020 at 00:31
Sodium fluoride is very sparingly soluble so simply dissolve your ammonium fluoride in water (very soluble) and add equi molar amounts of sodium
hydroxide and sodium chloride. Stand for a while and filter of the sodium fluoride and wash with water. Or you can use pure sodium hydroxide (2 moles)
and get som e ammonia gas to boot 
But ammonium bifluoride is much more useful than NaF. when molten it dissolves all sorts of refractory metal oxides. Its also quite stable if stored
in a tightly closed polythene/ polypropylene jar.