Re: Tanning theory of dichromated colloids (was gelatin

From: Katharine Thayer ^lt;[email protected]>
Date: 05/17/04-10:38:09 AM Z
Message-id: <>

MARTINM wrote:
> "So in this case they knew they already had Cr(III) but the EDTA inhibited
> the crosslinking?"
> I am not sure if this applies to Cr(III) specifically but certainly to
> "dichromate". If the quantity of EDTA (actually the dichromate/EDTA ratio)
> reaches a certain threshold, it will impair any crosslinking to take place.
> In former dye sensitized DCG systems EDTA used to be added as an electron
> donor for the dye.

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.

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? Thanks,
Received on Mon May 17 17:34:28 2004

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