# Does fluoroantimonic acid dissolve noble metals?

Hello,
Does fluoroantimonic acid dissolve noble metals? Nernst equation suggests that platinum would require pH ≈ −20.1 to be dissolved, using Hammett acidity function as an extension of pH scale it seems that it should dissolve in fluoroantimonic acid. On the other hand possiblility of dissolving gold depends on the exact value of acidity function as it would require pH ≈ −25.7 to be dissolved (fluoroantimonic is sometimes stated to have H0 = −31.3). However wikipedia says that Hammett acidity function of fluoroantimonic acid is in range: −21 > H0 > −23.

Calculations:

Reaction                    Standard electrode potential "pH" required to dissolve
$$Pt^{2+}+2e^-\rightarrow Pt$$ $$E^0=1.188V$$ $$pH=-\frac{1.188}{0.05916}\approx-20.1$$
$$Au^{3+}+3e^-\rightarrow Au$$ $$E^0=1.52V$$ $$pH=-\frac{1.52}{0.05916}\approx-25.7$$

Sources:

1. https://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)
2. https://en.wikipedia.org/wiki/Nernst_equation
3. https://en.wikipedia.org/wiki/Hammett_acidity_function
• I, for one, would not use potentials in aqueous solutions to predict redox thermodynamics in what is clearly a nonaqueous system (presumably HF solvent). Nov 21 at 2:12
• One of the components of fluoroantimonic acid, antimony pentafluoride ($\ce{SbF5 }$) is itself quite a strong oxidiser, and may end up being what causes the dissolution to occur, if any. Nov 21 at 6:25

Also see this video: THE STRONGEST ACID IN THE WORLD Fluoroantimonic acid (shows the reaction of $$\ce{HSbF6}$$ with magnesium, sodium and potassium)