[Rockhounds] concrete/cement - phosphoric acid

[J Bryan Kramer]

It may be slightly corrosive in the concentrated form, but it isn't toxic.
And as mineral acids go, it isn't especially strong with a PKa of +2, Citric
acid has a PKa of +3 but a strong acid like Hydrochloric has a PKa of -4. So
it is slightly stronger than Citric but 6 orders of magnitude weaker than
HCl. The lower the PKa, which is logarithmic, the stronger the acid.

If you look on many soft drink labels you'll see phosphoric acid is an
ingredient, approved by the US FDA for human consumption.

BK

On 10/23/07, Armando Afonso <armandoafonso at oniduo.pt> wrote:
>
> A sugestion: Phosphoric acid is used to clean sewage pipes of cement
> residues.
> Try it, with care. It is toxic!
>
>
>


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