Homebrew PCBs

On 03/08/13 04:12, Kerry Koppert wrote:
> Sodium Percarbonate (aka solid hydrogen peroxide) is a mixture of sodium 
> carbonate and hydrogen peroxide Na2CO3.5H2O2. When dissolved in water it 
> forms an aqueous solution of Sodium Carbonate and Hydrogen Peroxide. Mix 
> that with Hydrochloric acid and you get an aqueous solution of Salt, 
> hydrogen peroxide and gaseous carbon dioxide.

My concern would be the effect it has on the pH of the solution. The
Na2CO3 is going to react with the HCl and pretty much eliminate it if
you add it straight to the etch bath. Then you have to do the titration
steps from Kasten's book (or Adam Seychell's writeup) and adjust the
acid level appropriately.

Mixing with HCl separately might be another option, then freeze it to
get rid of some of the water and reduce it to H2O2. Although that might
not be possible if the salt content is too high...

(Begin brain-dump - ob disclaimer: I'm not a chemist, this looks
plausible but peer review would be gratefully received!)

Na2CO3 + 2xHCl => (2x NaCl) + H2O + CO2

If that's right, there's twice as much salt generated as water... we're
not using pure solutions so that water and salt will be dissolved into
the water already present in the acid. The question is, how much will
the salt content shift the freezing point, and can a domestic freezer
get cold enough to separate out enough H2O2 to make this worthwhile?

In any case, I'm fairly certain Oxyclean or something like it could be
obtained from the local supermarket or hardware store...

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/