Re: Chrome Alum Gelatin hardener

From: Suzu Sn <bromideshi@yahoo.co.jp>
Subject: Re: Chrome Alum Gelatin hardener
Date: Wed, 11 Feb 2004 15:19:34 +0900 (JST)

> You said formaldehyde bonds are easily broken by
> weak acids and heat.

What I said is that glutaraldehyde forms crosslinking that is
different in structure and more stronger than those formed by
formaldehyde or glyoxal in terms of resistance against acid and high
temperature attack.

> I said I did not recall getting the interpretation from
> the literature that formaldehyde bonds were so weak and I
> was curious as to why you did.

See James 4th edition as I mentioned before. All these things are
explained in detail. If you want, I can give you page numbers but if
you use the index it's easy to find.

> So Ryuji, can you tell me from what part of "The melting
> point of such* a layer will be higher than 100 (degrees)
> C." convinces you that formaldehyde bonds are, to quote
> you "... not very stable, and they can be broken with weak
> acid or high temperature." ?

The thermal stability of cross linking, which concerns about strength
of an individual cross link, is a different story from the "melting
point" which is a gross property as the whole gelatin. Anyway, you are
mixing the property (and the terminology) of single crosslink mixed up
with the macroscopic property and terminology. Do you get that?

> You mentioned cyclic linkages... (they were in fact at
> that time conjecture...) however in the same James'
> paragraph it also states that those links do not seem to
> account for the great stability of collagen -
> gluaraldehyde cross-links.

Conjecture? There were results using multiple techniques in 1970's and
forward. What are you referring to? Older edition of James? (which
was mostly conjectures, as you say, about the hardening mechanism of
glutaraldehyde. For this particular issue, you really need 4th
edition.)

> If another book told you something different, why don't
> you quote that information?

I'm just illustrating how the hardener research shifted over time. I
also pick up literature on gelatin capsule in pharmaceutical world as
well as publications by polymer community and industrial people like
Knox. I don't see anything contradictory as to hardening by
glutaraldehyde. Even in very recent patents of various inkjet and
other non-darkroom printing papers, whenever gelatin sizing is used,
glutaraldehyde is preferred over other aldehyde hardeners. This is
nothing to do with silver gelatin, needless to say.

> Easily done. All on my shelves.
> On what page does it say formaldehyde linkages are "...
> not very stable, and they can be broken with weak acid or
> high temperature."?

I said neither Duffin nor Zelikman and Levi talks about mechanism of
glutaraldehyde hardening, because they didn't have the data that
became available only later. But if you see James 4th edition, it's
very clearly there.

> Ryuji, all I am asking is for you to back up what you
> claim, and back down when you can not provide supporting
> refs. or personal experience of a relavent nature.

Almost all of what I said is very clearly stated in James 4th edition,
specifically in the chapter by Burness and Pouradier, as I said
before. Did you read that?

> Is that too much to ask?

Yes, because I already asked you to refer to Burness and Pouradier's
chapter. If you have difficult time understanding what they say, I can
help you but I don't feel like translating that article here.

--
Ryuji Suzuki
"Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)