Fixatives and their names

Miller, Mark A. (mamiller@wista.wistar.upenn.edu)
Wed, 15 Jan 1997 11:25:28 -0500

Isn't formalin just the 37% aqueous solution of
formaldehyde? Formaldehyde is a gas, H2C=O.
Paraformaldehyde is a solid, sparingly soluable
in water. Paraformaldehyde is a polymeric form
of formaldehyde, (H2C0)N.

If you are stirring a powder into water ovenight
(or a shorter time in warm aqueous NaOH)
to make your fixative, you are making a solution
of paraformaldehyde (probably 1 or 2% w/v).

If your fixative comes out of a big plastic jug
from Sigma (etc.), it is formalin.

Mark Miller
mamiller@wista.wistar.upenn.edu