I always liked the post where the pcb maker was going to "distill'
the H2O2 to make it stronger.
;)
Myc
--- In Homebrew_PCBs@yahoogroups.com, Len Warner <novost@...> wrote:
>
> At 4:16 am ((PST)), Sat Jan 20, 2007 Stefan Trethan wrote:
>
> >The BBC just had a piece about the trial of those would-be bombers.
> >[snip]
>
> Moral: remember to ask for a discount on quantity ;-)
>
> >It may still be possible to buy small quantities of H2O2 for PCB
etching
> >at those shops, especially if one is not afraid of questions and
some
> >interest.
>
> On Friday last I went into our local chemists and checked with the
> pharmacist whether she stocked hydrochloric acid (which I had
> bought from her some long time ago) and hydrogen peroxide.
>
> The answer was yes in both cases, though she called the HCl
> "Spirits of Salts" - which is how it is labelled. The H2O2 was
> stocked in 2 strengths: 6% (20vol) & 9% (30vol). A bit weak
> for regenerating CuCl, but perfectly adequate for HCl-H2O2
> etching.
>
> I wasn't asked "Would you like acetone with that?" ;-)
>
> I did this research in delayed response to someone's
> claims of not being able to buy chemicals in the UK,
> which he has repeated despite my reply pointing out
> that one can (and yes, IPA is still available from Maplin,
> too, shelf stock last time I looked).
>
> Might I also urge people to identify the active ingredient
> and its _concentration_. Most of us easily can look up the
> etymology of "muriatic acid" and such like common names,
> but we can't read the label on _your_ bottle of chemical to
> know the concentration - you have to tell us.
>
> [A recent recommendation to prepare PCB with a 30sec
> pre-etch in HCl-H2O2, which could have stripped most
> of the copper at the strengths some have available. ;-)
> Please remember that people using your advice may not
> have the benefit of your experience.
>
> Another post identified soda ash with washing soda -
> although both are sodium carbonate, IIIRC those pretty
> crystals of washing soda contain ten molecules of water
> of crystallization - so a 1% solution of washing soda
> is a lot weaker than a 1% solution of sodium carbonate.]
>
> Whereas hydrochloric acid seems usually to be supplied in
> the mid-30% range near or at its maximum concentration,
> H2O2 is usually diluted. Pharmacy shelf strength as a
> general bleach, disinfectant and and sterilizer is 3, 6 or 9%,
> beauty parlour strength seems to be around 30% and
> anything more is industrial going on rocket fuel strength
> - and could incinerate you.
>
> Also remember that H2O2 is de-stabilized by metal ions
> and other particulate matter, so (a) it isn't a good idea
> to store it in another bottle than it was supplied in and
> (b) don't expect to part-used HCl-H2O2 to have any
> shelf life at all.
>