[pure-silver] Re: Pyro in a Jobo Processor
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 18 Mar 2005 12:22:26 -0500
One of the problems is that the chelated metal can be even more
effective than the unchelated metal is causing oxidation. This is
particularly true of EDTA. I read somewhere (and wish I had written
down the citation) that asymmetric chelating agents are less prone to
this problem. I assume this is why we now see DTPA
(diethylenetriaminepentaacetic acid) and similar compounds being used
instead of EDTA in photo products.
I am curious about your statement "my developer at 5gm/L", what
developer are you using that has such a low concentration of sulfite.
This is usually the concentration that one sees in the working solution
of a one shot developer.
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of John Black
Sent: Friday, March 18, 2005 12:00 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Pyro in a Jobo Processor
> The main source of metal impurities would be the sodium sulfite itself
> rather than the water used to make the solution. Iron and copper are=20
> the metals usually implicated in the oxidation.
>
> A well stoppered bottle to keep the oxygen from the solution is=20
> probably the best solution
Good point... I have had no problems so far keeping it as a saturated
solution in glass bottles with white rubber lined phenolic caps. But
when in my developer at 5gm/L it degrades within about a month, even in
the presence of EDTA.
JB
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