From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-02-11 14:07:00
--- In buildcheapeeg_at_yahoogroups.com, "Joerg Hansmann" <info_at_jhansmann.de> wrote:
> A possible source where the DC offset comes from is the
> input stage bias current that charges the electrode surface
> by electrochemically altering it. If this mechanism can be
> confirmed there are several approaches to avoid this charging:
>
[snip]
Add this to the list:
6) Add a layer of AgCl. :-) Remember that gold or steel electrodes
have high offsets, so pure silver is probably not an exception.
>
>
> > Please try
> > chloridizing the electrodes too ...
>
> At first I thought: No problem, but when I read an old "elektor"
> article (german edition, no. 196, p 68, april 1987) about
chloridizing
> silver electrodes some questions arose:
>
> What purity should the NaCl have ? Will normal houshold quality be
enough ?
I'm not sure. You can probably get medical grade salt at the
pharmacy, but there's no harm in trying regular salt first.
> Do I really have to use destilled water for the saline ?
I think so. Our drinking water contains a lot of different salts and
pollutants as well as small amounts of chlorine and flouride that are
added at the treatment-plant. I think you can buy distilled water in
most grocery stores or supermarkets.
> Is the recommended 0.9% concentration referred to volume or to
weight ?
I don't think that is important if the concentration only affects the
speed of the process, not the outcome. Anyway, my guess is by weight,
because it is much more straightforward to calculate and measure.
> Do I really have to sacrifice a silver electrode for the Kathode
> (The electrodes to be chloridized are attached to the Anode (+)),
> or would graphite also be OK ? (I do not see any reason why the Na+
> ions should be replaced with Ag+ ions ...)
Yes. I've read that you might want to reverse the current for a few
minutes to strip the electrodes of any residue chlorides before
starting the chloriding process. I've all but forgotten my (junior-)
high-school chemistry, but I think that if you use a graphite
electrode you will produce chloride gas at that point. And that's bad
for your health you know. :-)
Regards,
Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:38 BST