Re: dichromated colloids

"Mytych, P., Karocki, A., Stasicka, Z. 2003. Mechanism of
photochemical reduction of chromium (VI) by alcohols and its
environmental aspects. J. Photochem. Photobiol., Ser. A., vol 160, pp
163--170.

Their motivation is to understand a potential mechanism to reduce one
of the "priority pollutant," that is, chromium (VI) such as
dichromate. They tried a range of alcohols and pH, with oxygenation or
with deoxygenation. It seems that lower pH is preferred in the case
of Cr(VI) likely because HCrO4- is more active in the reactions
involved."

That's very interesting. Thanks a lot, Ryuji.

"There is another piece of puzzle in alcohols. Reports coming from
Lafond's or Mannivanan's groups using PVA keep mentioning that they do
not find Cr(III)-PVA complex. THis is very different from what Grimm
et al found with a PVA model system 2,4-pentanediol. I am running out
of time but I'll come back to this later. That paper above gave me
some idea."

Looking forward to hearing about that.
Searching for further information about Cr hardening, I run into a mail I
received some time ago:
"...Cr VI has got to be reduced before it can harden and that
process is carried out with the help of violet light enabling the Cr VI to
grab electrons from the most oxidizeable bits of gelatin like -CHO
aldehyde bits to make Cr III. I am not clear if this oxidation greatly
hardens the gelatin on its own I suppose it may contribute."

Do you see how those "-CHO aldehyde bits" contribute to Cr(III) formation?

Martin

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, May 20, 2004 12:28 AM
Subject: dichromated colloids

> From: MARTINM <martinm@SoftHome.net>
> Subject: Re: Tanning theory of dichromated colloids
> Date: Sun, 09 May 2004 12:16:43 +0200
>
> > "...Incidentally, primary alcohols, alkenes and alkynes can also be
> > oxidized to carboxylic acid with strong oxidizing agents like
> > permanganate or chromium (VI)."
> >
> > That has been interesting me for quite a while. Do you know what kind of
> > condition (pH/temperature/time) is required to initiate that reaction?
>
> Just found this paper:
>
> Mytych, P., Karocki, A., Stasicka, Z. 2003. Mechanism of
> photochemical reduction of chromium (VI) by alcohols and its
> environmental aspects. J. Photochem. Photobiol., Ser. A., vol 160, pp
> 163--170.
>
> Their motivation is to understand a potential mechanism to reduce one
> of the "priority pollutant," that is, chromium (VI) such as
> dichromate. They tried a range of alcohols and pH, with oxygenation or
> with deoxygenation. It seems that lower pH is preferred in the case
> of Cr(VI) likely because HCrO4- is more active in the reactions
> involved.
>
>
> There is another piece of puzzle in alcohols. Reports coming from
> Lafond's or Mannivanan's groups using PVA keep mentioning that they do
> not find Cr(III)-PVA complex. THis is very different from what Grimm
> et al found with a PVA model system 2,4-pentanediol. I am running out
> of time but I'll come back to this later. That paper above gave me
> some idea.
>
> --
> 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)
Received on Thu May 20 02:04:07 2004