dichromated colloids (Sasaki et al)

From: Katharine Thayer ^lt;[email protected]>
Date: 06/27/04-04:52:09 AM Z
Message-id: <40DEA6CD.16BE@pacifier.com>

I think this is the right subject line, but I can't locate the original
discussion that this goes with.

At any rate, this refers back to an article that was recommended to me
in my search to understand the chemistry of the gum process:

Sasaki, Masako; Honda, Ken-Ichi; and Kikuchi, Shin-Ichi. "Studies on
Photosensitive Dichromated Materials." Report of the Institute of
Industrial Science, The University of Tokyo. (the date is blurred on my
copy, but if I remember right this was from 1977 or 1978)

This was by far the most useful paper that I've found as far as
dichromated PVA, and I thank Martin Mueller for pointing it out to me
and going to some trouble to get it to me, but it contains errors that I
wanted to point out to anyone who might be interested in consulting this
paper. Knowing this may save you the days I spent scratching my head
over the stoichiometry of the model they propose for the crosslinking. I
thought it must be because my chemistry is 25 years behind me and I was
forgetting something important that I couldn't follow their
calculations, but on finally swallowing my pride and turning to an
expert to tell me what I was doing wrong, it turns out it's not me;
there are errors in the numbers and in the calculations. So this is how
I'm told on good authority it should be:

On Page 34, middle of the page, the equation PVA:Cr(VI) =
the answer should be 1: 0.252 rather than 1:0.52.

and a bit farther down, they say that they assume the degree of
polymerization of the PVA to be 1400 and the molecular weight to be
6000. Given their assumptions, the molecular weight of the PVA must be
60,000, not 6,000. Since their model is based on PVA: Cr(VI)=1:0.52 and
molecular weight of 6,000, their model may not be a useful model.

And on page 35, "In case of the photoreduction of dichromated gelatin
solution of 5 ml containing etc etc etc: this should be 50 ml, not 5
ml, otherwise the following calculations don't make sense.
Katharine Thayer
Received on Sun Jun 27 11:48:22 2004

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