Re: Help with what I believe is a hardening issue

OHHHH, Tom, my very very bad! Thanks for clarifying.

Question, though: for our purposes of hardening gelatin, does
paraformaldehyde not work?? Could we not mix up a solution of the powder in
water at time of use and throw? Or will it not harden the gelatin?? And,
if we can mix up a solution of it that can do the job of formaldehyde, is
there a percentage you would suggest?
Chris
----- Original Message -----
From: "T. E. Andersen" <postlister@microscopica.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, November 10, 2004 9:43 AM
Subject: Re: Help with what I believe is a hardening issue

> Christina Z. Anderson wrote:
>
>> Candace,
>> I feel for you...
>> Formaldehyde is 37% solution of paraformaldehyde powder. You can get
>> it from Tri Ess Sciences in Burbank CA (800-274-6910) and mix your own
>> solution.
>
>
> This is not the case!
>
> Formaldehyde is a gas. Formalin is an aqueous solution of about 37%
> formaldehyde, with the addition of up to 15% methanol, and sometimes other
> additives as well.
>
> A pure solution of paraformaldehyde is very unstable. It will suffer
> quickly from oxidation (see Ryujis and my posting on that). After a fairly
> short time it will also start to polymerize, due to the lowered pH
> following the formation of formic acid.
>
> I use it for histology, and it is made fresh for each use. Depending on
> the application, it will keep from a day or two, up to a week. It is NOT
> RECOMMENDED to make the solution at home. It requires heating to 70*C,
> while adding sodium hydroxide. I can testify that the fumes from hot
> formaldehyde solution are vicious! Unless you have the proper equipment
> and skills, DON'T DO IT!
>
>
> Best regards,
>
> Tom Einar
>
>
Received on Wed Nov 10 08:56:48 2004