[pure-silver] Re: Adding Pot Bromife to PC-TEA
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Tue, 11 Jan 2005 14:30:30 -0500 (EST)
From: Jordan Wosnick <jwosnick@xxxxxxxxxxx>
Subject: [pure-silver] Re: Adding Pot Bromife to PC-TEA
Date: Tue, 11 Jan 2005 12:24:50 -0500
> Your hypothesis seems very reasonable. I was recently reading that
> one of the major organic chemistry 'discoveries' of 2004 (a
> palladium-catalyst-free microwave-induced Suzuki reaction,
> ironically :) has been retracted -- it turns out that a nearly
> undetectable amount of palladium salt contaminating a batch of
> reagent grade sodium carbonate was the real catalyst.
>
> It seems like ascorbate developers are particularly susceptible to
> this. Water quality is probably an issue too -- iron everywhere!
Well, palladium is known to be a useful dopant to incorporate into AgX
crystals for some purposes. So are many other metals.
Since XTOL contains a large amount of DTPA yet has some problems, I
suspect that the problem is related to species whose catalysis cannot
be poisoned by that type of ligands. My strong suspicion goes to iron,
which is also used as a dopant in films, but also present in photo
grade chemical stocks.
I suspect 2,2'-bipyridine, 1,10-phenanthroline or their derivatives
would cure this problem but these are not as safe chemicals as other
ingredients of my ascorbate developers, and so I didn't use them.
(Plus, making emulsions is a lot more interesting and direct to the
photographic effects than developers, so my time goes to that
direction.)
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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