Re: Tanning theory of dichromated colloids (was gelatin

From: Katharine Thayer <kthayer@pacifier.com>
Subject: Re: Tanning theory of dichromated colloids (was gelatin
Date: Fri, 07 May 2004 10:13:27 +0000

> I answered this question cryptically, assuming that you know very
> well yourself the similarities and differences between gelatin and
> collagen.

I found nothing cryptic because you didn't mention this and switched
the issue to gum.

Comparing gelatin sol and leather is absurd. In sol state gelatin is
dispersed in water and can react well with water soluble hardening
agents like aldehydes. Leather is a completely different
problem. Besides it's not degraded to gelatin form, and it contains a
lot of other stuff that is not a part of gelatin, there are a lot of
other factors getting in the way: osmolarity of the tissue, the rate
of penetration of the crossliniking agent to the tissue (especially
because the surface gets hardened first with fast acting agents and
further hardening must penetrate through this), etc. In case of
leather, hydrophilicity of tanned leather and acceptability of
leather-conditioning agents is another problem. Also, you missed to
point out that glutaraldehyde is much superior leather tanning agent
than formaldehyde. Formaldehyde is much cheaper and more readily
available so it gets used whenever its performance is comparable to
glutaraldehyde.

> But on further reflection (I'm mopping floors so have lots of free
> mental space to reflect with) it occurs to me that by evoking the
> hardening of gelatin with chrome alum to explain the chemistry of gum,
> you are in effect buying into the "tanning" theory of dichromated
> colloids, whether you realize it or not.

I think what you are doing is playing with words. Look at the chemical
building blocks and what are acting on them under what condition.

From: Katharine Thayer <kthayer@pacifier.com>
Subject: Tanning theory of dichromated colloids (was gelatin
Date: Fri, 07 May 2004 08:14:05 +0000

> My goal is to show that the "tanning" model is not at all useful to
> explain the chemistry of dichromated gum.

What an anti-scientific mind it is. You already have your conclusion
and you are simply looking for whatever pieces you can use.

--
Ryuji Suzuki
"All the truth in the world adds up to one big lie." (Bob Dylan 2000)