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At almost 300°C, $\ce{CaF2}$ reacts with sulfuric acid and this reaction produces $\ce{HF}$. Is there any way to make a relatively dilute (10-20%) hydrofluoric acid with $\ce{CaF2}$ as the source of fluoride ions without that much amount of heat?

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  • $\begingroup$ CaF2 is already source of F- anions. $\endgroup$ – Mithoron Jan 31 '18 at 17:59
  • $\begingroup$ But the synthesis described above is too dangerous to be safe to do in my lab. Of course I know that $CaF_{2}$ is a source of $F^{-}$ ions. $\endgroup$ – L.Gyula Jan 31 '18 at 18:06
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    $\begingroup$ Well, if you really need acid, then better buy it. $\endgroup$ – Mithoron Jan 31 '18 at 18:11
  • $\begingroup$ But I do not need even 100ml of a 5% solution of it and I do not want to store that much of such a nasty chemical which I won't need anymore $\endgroup$ – L.Gyula Jan 31 '18 at 18:17
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    $\begingroup$ HF is pretty nasty stuff... can you substitute something such as ammonium acid fluoride, NH4HF2 (which is almost as bad, admittedly)? $\endgroup$ – DrMoishe Pippik Feb 1 '18 at 1:58
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In desperation, for some unknown reason, I need 15% aqueous $\ce{HF}$. What do I really need? A weak solution of $\ce{H+}$, say about pH 2. And a solution of fluoride ions to wreak havoc on some unsuspecting metal or glass(Ooops, I may have given away the secret).

My subconscious suggests that I could get them from two different sources, like $\ce{NaF}$ and $\ce{HCl}$. Yeah, that'll work.

Maybe. Maybe even with $\ce{CaF2}$(The use of $\ce{H2SO4}$ with the calcium salt suggests the reason was to precipitate the $\ce{CaSO4}$ and flash off the $\ce{HF}$, thereby separating, not just generating, the $\ce{HF}$).

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