Alternatives to Formalin/Formaldehyde?

J. A. Kiernan jkiernan at
Mon Mar 27 09:50:23 EST 1995

In article <eeeD61327.GyB at> eee at (Mark Thorson) writes:
>From: eee at (Mark Thorson)
>Subject: Re: Alternatives to Formalin/Formaldehyde?
>Date: Sun, 26 Mar 1995 03:30:07 GMT

>What's the difference between formalin and formaldehyde?  I've read
>that formalin is commonly used for chemical sterilization of food
>processing equipment.

    Formaldehyde = HCHO (a gas)
    Formalin     = 37-40% w/w HCHO in water. Actually consists
                   largely of methylene hydrate and low polymers.
                   Some methanol is added in manufacture, to
                   reduce polymerization.
    Paraformaldehyde = solid high polymer of HCHO. Depolymerizes as it
                   dissolves (typically in a physiological buffer; won't
                   dissolve in pure water) at 60C.  Used as a source of
                   methanol-free formaldehyde (methylene hydrate),
                   especially in fixatives for electron microscopy.

                                     John A. Kiernan
                                     Department of Anatomy
                                     Univ. of Western Ontario
                                     LONDON, Canada  N6A 5C1
                                     e-mail: jkiernan at

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