Re: Glutaraldehyde: a different kind of cautionary tale

  Lots of snipping...
> of the more prevalent sugars (18% of total sugar content)
in the gum.
>
>
> I was thinking this might explain why chrome alum didn't
work very well
> when I was doing my gum-hardening experiments for
painting, because of
> the relatively low proportion of carboxyl groups in the
gum (relative to
> gelatin). But how to explain why glyoxal worked very well
to harden gum,
> when there are even way fewer amine groups available in
gum than
> carboxyl groups? Either glyoxal links to something other
than amine
> groups in crosslinking gum, or..... it makes a great lot
out of a very
> few amine groups, or.......something.
>
> I didn't (and probably won't, given my history with this
substance) try
> hardening gum with glutaraldehyde. It would be interesting
to see
> whether it works as well as glyoxal. Since there are very
few amino
> groups, (and of those little and none is lysine and
hydroxylysine which
> are said to be the two amino acids that link in
glutaraldehyde hardening
> of gelatin)-- if glutaraldehyde works for gum, it must
work by an
> entirely different mechanism, or...... something.
>
> I think all this shows is that the chemistry of gum
crosslinking is
> probably quite different from the chemistry of gelatin
crosslinking,
> which I already knew, and I wish to goodness people would
stop telling
> me that if I would only read this or that about gelatin
hardening, I
> would know all I need to know about the chemistry of the
gum process.
> Sorry, I don't THINK so!
>
> Katharine Thayer

 Was there also a large difference in pH? That might have
an effect. Chrome alum likes to work in an acid environment,
glutaraldehyde in alkaline.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com