Adam- thanks very much for the information and link.
What kind of indicator do you use? My chem student friend seemed to
think that Bromphenol Blue was some kind of throwback to the dark ages
and very difficult to find.
Grant
--- In Homebrew_PCBs@y..., Adam Seychell <adam_seychell@y...> wrote:
>
>
> grantfair2001 wrote:
>
> >A chem student tells me the pH of the solution outlined in:
> >
> >http://www.dnai.com/~rexa/Projects/CuCl_ech.html
> >
> >would be just as good an indicator of needed chemical additons as the
> >lengthy lab methods in the above article. A pH probe is more
> >convenient and much cheaper than the lab equipment the article says is
> >necessary. For example, Corning sells a pH probe for $40.
> >
> >Does anyone know if the student is right? What pH level would be
> >optimum, and what would variations mean need to be added to the brew?
> >
> >Grant
> >
> >
>
> pH isn't a good indication for HCl concentration of this etchant. pH
will be very insensitive to acid concentration because HCl is a strong
acid. (almost all HCl goes to H3O+ and Cl-). i.e pH will always be
very very low, even for a small amounts of acid. Acid/bace titration
is the only reliable method.
>
> However the article below mentions that a very sensitive
conductivity meter is often used to automate HCl addition on
commercial etching equipment. My guess this isn't so straight forward.
At the very least the probe would require careful calibration across
temperature and HCl concentration.
>
> http://www.pcbfab.com/iepart3.html
>
> I have the glassware to do acid/bass titrations and it isn't that
difficult or expensive as it may sound (class-B 50 ml burette AUD$55).
One good thing about this equipment is it will last you forever and
doesn't require maintenance unlike pH probes. The most difficult part
would be making up your standard solutions of sodium hydroxide. Best
bet would be to visit your local university chemistry department and
ask for some.
>
> I made the mistake buying some cheap glass/plastic equipment from a
school science supply. It was total rubbish, errors greater than 10%
and wasn't even that much cheaper than the proper German made stuff
that I later got from a laboratory supplier.
>
> good luck