[Rockhounds] concrete/cement - phosphoric acid

[Axel Emmermann]

Household (kitchen) cleaning gels often have 1% or so phosphoric acid in
them.
Great for cleaning pyrite and even calcite. 
Brings great luster to shiny specimens.
Don't let the calcite soak too long though! ;-)))

Axel

> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com 
> [mailto:rockhounds-bounces at lists.drizzle.com] Namens J Bryan Kramer
> Verzonden: dinsdag 23 oktober 2007 13:48
> Aan: Rockhounds at drizzle.com: A mailing list for rock and gem 
> collectors
> Onderwerp: Re: [Rockhounds] concrete/cement - phosphoric acid
> 
> 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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