[pure-silver] Re: D-76 and variations
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Tue, 29 Nov 2005 14:06:46 -0500
I routinely use the contents of a plastic jar of Phenidone that is
probably 20 years old and still as active as ever. Phenidone solid is
quite stabile and in the same class as hydroquinone and Metol as opposed
to Amidol and Glycin.
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of John Black
Sent: Tuesday, November 29, 2005 1:58 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: D-76 and variations
> I found this article on the practical storage performance of various
> D76
> derivatives: http://www.udmercy.edu/crna/agm/phenvitc.htm
>
I generally agree with his findings but the work is at least 5 years old
and has some gaps in it. For instance, XTOL presently contains
dimezone-S not phenidone. The patent formula published for Xtol in A&T
lists dimezone-S I believe (where have I put that book...). The aqueous
longevity of dimezone-S is much longer than phenidone, even in heavy
sulfite solution. I cannot keep water stock solutions containing
phenidone for 6 months. Even with large amounts of sulfite, it rarely
lasts more than a few weeks. Phenidone solutions in glycols last quite
well for a year or more as long as water doesn't enter the picture until
right before use.
> It is well written and laid out, so we can make our own judgement on
> the experimental thoroughness and repeatability.
His inability to derive a straight line for dry phenidone activity may
indeed be due to his lack of precision in weighing. This would need to
be repeated with a better balance. His Xtol activity vrs time curve is
a bit erratic. Since it is made from the same stock solution each time,
it should be flatter. There was obviously another variable at work.
The most interesting data from his activity/time chart was the stability
of dry phenidone. I have read several sources (A&T for one) that
contends that phenidone in the dry state is quite unstable and should
not be more than 6-12 months old for use. I am still working on a
bottle of dry phenidone that is over 7 years old and still as active as
when new. It has been stored in amber glass, tightly stoppered at room
temperature.
>
> Interestingly, it throws suspicion on plastic containers wrt D76
> keeping qualities.
Some plastics are indeed quite gas permeable. I don't know which are
the best but PETG seems to be almost as good as glass. Glass is however
cheap, plentiful and reusable. I use glass and shall continue to do so.
JB
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