On 18 May 2010 at 13:43, germeten wrote:
> Another post mentioned it; dilute hydrofluoric acid added to mixes or
> as a wash, should strengthen and harden lime & gypsum cretes quite a
> bit, because fluoric acid will bind with calcium to form fluorite
> crystals, the same kind that strengthen your teeth & bones.
No, you got it wrong. The mineral in teeth and bones is hydroxyapatite, not fluorite. Fluoride
does turn hydroxyapatite on the surface of the teeth into fluorapatite, which is harder, but
more importantly, more acid resistant. Fluoride has practically no other biological role.
As a chemist I would strongly discourage the use of hyrdofluoric acid on a building site.
Niel
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