Re: insolubilisation

Peter Marshall (petermarshall@cix.compulink.co.uk)
Mon, 26 Feb 96 18:00 GMT

> Peter
>
> Thanks for the Tetris information. The addiction, not mine, is still with
> the original.
>
> I suggested to Keith Dugdale that he might ask you for an article.
>
> And now to our muttons. I had assumed that when ions are transferred from
> dichromate molecules to polymers to effect insolubilisation when the dichromate
> molecule is affected by the light, those ions were oxygen ions. You said
that
> it is probably a secondary rather than a redox (reduction and oxidation)
> reaction and you gave the reaction between chrome alum and gelatine as an
> analogy. I am sorry if I have misquoted you

It would probably help others on the list if you kept matters such as Tetris
out of it - already there will be some thinking it is some new trick that
you have for producing gums. What is tetris and where can we buy it?.... Judy
will be fomenting over yet another brit conspiracy.

Keith may get something from me at some time - whether he wants it or no.
I have one or two points to sort out on something I wrote at Christmas.

To dichromate/colloid reactions. First the redox must involve something
other than the chromium compound - this gets reduced so something must get
oxidised. Dichromate is not too fussy about what it chews up, and this is
likely to be part of the colloid. The likely fate of most of the oxygen in
the dichromate is as water. I don't have any books that deal with
these reactions in detail, but assume that the gum becomes insoluble
through the presence of the chromium(III) ions (as in hardening using chrome
alum) rather than by the oxidation reaction.

I think I have read something about the chemistry involved in this hardening
on this list.

A Ph.D in Chemistry only evidences that one has spent 3 years or so scratting head
down in a peculiar corner of the backyard (I speak from experience). I think I
blinked while colloid chemistry was being dealt with in my undergrad course.

Of course we chemists (or ex-chemists in my case) are generally in favour of a quiet
life and are likely to nod politely when confronted with chemical ignorance on a
grand (or even king-like) scale:-) I'm sure that I or even others more qualified
would be willing to suitably doctor anything chemical you care to write on the
subject.

Peter
petermarshall@cix.compulink.co.uk

PS. To save _further_ unnecessary comments: Tetris is a game. Netris is an even
smoother version of it, suitable for multiple players on a single Windows PC or over
a network. Inetris lets you play it against others over the Internet. If really
desperate, got to:
http://www.dur.ac.uk/~d405ua/ * fiction, art, links and...
>> s0ftware f0rge programs * entertainment : MIDI utilities * Win 3.1/95
>> latest feature * iNETRiS 2.0 internet tetris release! * req. Win 3.1+