There is news media story current here in Australia that hydrogen peroxide
is about to be, or has been, placed on the controlled chemicals list because
of its potential in terrorist bomb manufacture. This has the hair-dressing
industry in a quandry. Maybe the pcb homebrewer should join that debate?
Bill
----- Original Message -----
From: "Len Warner" <yahoo@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, October 09, 2006 10:30 PM
Subject: [Homebrew_PCBs] Re:Removing ferric chloride stains
> At 9:52 am (PDT) Sun Oct 8, 2006, adriano-sar wrote:
>>At 5:44 am (PDT) Tue Oct 3, 2006 leon_heller wrote:
>> > I was curious about the stuff sold for removing ferric chloride
>> > stains...oxalic acid crystals and rubbing with rhubarb leaves
>> > should work just as well, they contain oxalic acid.
>> > Its quite poisonous, BTW.
>>
>>use the muriatic acid with hydrogen peroxide and does not remain
>>residual, once used it is neutralized with of common bicarbonate
>
> Fisio, if you look back in the message archive you will see that
> this thread is for people who already have ferric stains and would
> like to be rid of them.
>
> They have already been advised that there are cleaner etchants.
>
> If you really mean to recommend HCl+HOOH as a stain remover,
> isn't this just a little bit aggressive for the task? (It will attack
> natural fibres and most common metals.)
>
> I would endorse the use of oxalic acid.
>
> Apart from its toxicity by ingestion, it is a relatively harmless
> fruit acid. As such, it is easily mistaken for ordinary culinary
> ingredients such as citric acid or cream of tartar [potassium
> hydrogen tartrate]. If you buy in bulk make sure it is labelled
> clearly and not stored near foodstuffs.
>
> It is the active ingredient in the "Stain Devil" rust stain remover,
> which comes in safety packaging.
>
> The toxicity is because calcium oxalate is not very soluble.
> Once the oxalic acid has been absorbed from the gut it
> combines with calcium ions in the blood to form a precipitate
> which clogs the kidneys, leading to kidney failure. Hence
> the occasional poisonings of the ignorant or starving by
> rhubarb leaves. The stems contain much less oxalic
> acid and are delicious and safe to eat. Even so, I prefer
> to eat mine with evaporated milk, just to be sure the residual
> oxalic acid is bound in my gut rather than my bloodstream.
>
> As a stain remover, rhubarb leaves seem a good way of
> replacing ferric stains with chlorophyll stains ;-)
> (NB: chlorophyll dissolves in alcohol or bio-detergents.)
>
> Oxalic acid acts as a mild reducing agent and converts the
> brown ferric ion to pale green ferrous. I'm guessing the
> ferrous ion is more water-soluble than ferric.
>
> Other common chemicals which _might_ work are:-
> ∗ citric acid [lemon juice], (nowadays used in preference to chromic
> acid to pickle new stainless steel to remove surface free iron);
> ∗ cream of tartar + glucose, (the kind of slow reducing agent used
> to deposit silver mirrors); or
> ∗ acetic acid [vinegar], (acetates are often very soluble).
> None is specially toxic and they might already be in your kitchen.
>
> Perhaps Mycroft would care to comment on these suggestions?
>
>
> Regards, LenW
>
>
>
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