Re: Is there a way of testing the strength of 10% formalin?

From:Mark Ray <>

Dear Annette,

Allowing formaldehyde to chill below the recommended storage of  ~10C will
result in the polymerization of some or all of it to paraformaldehyde.  This
will be evident as a white precipitate in the bottom of the bottle.  Warming
precipitated bottles to room temperature will not restore the formaldehyde
concentration.  It's possible that heating at 60C until the precipitate
disappears may restore it, but this may not be a practical solution for you.
The simplest procedure for accurately determining formaldehyde concentration
is a titration.  I can provide the procedure if you like.

At any event, discontinue using bottles which show  evidence of
precipitation;  their formaldehyde concentration will probably have been be
reduced to a level which will not produce suitable fixative when diluted

Hope this helps,
Mark Ray
EK Industries
----- Original Message -----
From: <>
To: <>
Sent: Tuesday, March 06, 2001 11:52 AM
Subject: Is there a way of testing the strength of 10% formalin?

> Hello histonetters,
> At our hospital laboratory the staff have been making up 10% formal saline
> for 40 years. An odd time one would come across a dud bottle of 38-40%
> formaldehyde and discard.
> Recently however there has been a lot of dud bottles and I'm wondering is
> it the unseasonally cold spell of weather. The temperature in the Chemical
> store in the yard may have dropped well below (-7min.) the recommended
> 10-25C some nights and I'm wondering would this result in weak formalin.
> There also is an uncharacteristic clear red tinge to blood stained
> specimens  as if it had a higher than usual alcohol content. (We decided
> not to change over to NBF years ago as it works fine for most Immunos. We
> are in the UKNeqas ICC and doing OK.
> I thought even if the temp. dropped below 10C and subsequently was brought
> up to room temperature and diluted to make 10% formal saline then it would
> be fine. Does anyone have any experience of this kind of thing???
> Any thoughts ?? I have asked the supplier for a "certificate of
> conformity" for this batch and the date of manufacture and it is pending.
> There is a use by date on it of Oct 2001. Is there a way of testing the
> strength of the formaldehyde or would a low pH indicate a deteriorating
> solution.
> Annette Ryan
> Medical Laboratory Technologist
> Histology Laboratory
> Our Lady of Lourdes Hospital
> Drogheda
> Co Louth

<< Previous Message | Next Message >>