Re: Tanning theory of dichromated colloids (was gelatin

From: Katharine Thayer <kthayer@pacifier.com>
Subject: Re: Tanning theory of dichromated colloids (was gelatin
Date: Mon, 17 May 2004 16:38:09 +0000

> But I have the same question about this as about the statement in
> Duncalf & Dunn. If you put the EDTA with Cr(VI) and it keeps the
> crosslinking from happening, how do you know where the inhibition
> occurs? The other observation, which shows that EDTA can dissolve
> hardened PVA, is more compelling to me, but is still indirect.

EDTA makes stable complex with hexacoordinate Cr(II) and Cr(III) but
chromium of higher oxidation states form compounds like oxides, mixed
metal oxides, halides, etc. but not the form similar to EDTA complex
with Cr(III).

> And this dye sensitization I think is the same thing that is referred to
> in Kosar as "optical sensitization" which is what I asked someone to
> explain to me a while back and got no answer. Can you explain quickly
> how this works?

Why don't you find out who used that term and read the original work?

There are many different kinds of sensitization known in imaging
technology and that term "optical sensitization" is too general.

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)