[BetaAmyloid]

Weird... I was always under the impression that sulfuric acid had a pKa around hydrogen iodide.  Don't know where that misinformation came from.

Click pK_a Values Click

pK_a of hydroionic acid is -10 and sulfuric acid is -3.

Thanks Borek!

[researcher]

That works better than the bisulfate method I outlined above, lower temperatures needed.
Of course, conc. sulfuric and solid NaCl are needed.  Aqueous solutions give you nothing.

are you sure it doesn't work with aqueous solutions? I had read somewhere that the industrial method was with aqueous NaCl.

[408]

It may with concentrated solutions, followed by distilling out the aqueous azeotropic acid (~37%).  Dilute is likely useless for preparatory work(Unless industry has some odd method).  Using concentrated acid and solid NaCl is what I have seen in preparatory books for making solutions of HCl in various solvents.