[Histonet] alcoholic formalin

lpwenk <@t> sbcglobal.net lpwenk <@t> sbcglobal.net
Fri Oct 1 17:25:12 CDT 2004

Depending upon the who's procedure you are using, the final alcohol percent
is somewhere between 60-80%. The final formalin percent is 10% (= 4%

We make ours up in a discarded plastic one gallon container. One quart is
about 0.95 L. So 1 gallon = 4 quarts = 3.8 L = 3800 mL.

Figuring it out mathematically, and rounding amounts up or down to make it
slightly easier to measure (so our "measurements" are accurate to within
about 2.5 mL, but the solution still does it's job):

- 2700 mL of 95% alcohol
- 905 mL of d. water
- 95 mL of 40% formaldehyde (conc)

We use the same gallon jug(s) over and over. The easy way to make the
alcoholic formalin is to:
- measure the 2700 mL of 95% alcohol, pour into gallon container, and mark a
line on the container with a black permanent marker, and label this line
"95% alcohol"
- then measure and add the 905 mL of d. water, and again mark and label the
line for "d. water".
- finally measure and add the 95 mL of 40% formaldehyde, and again mark and
label the line as "40% formaldehyde".

After that, when the jug is empty, grab the jug, and fill up each solution
to the marked line, eye-balling it. No more graduated cylinders needed. Fast
and easy, and though not as accurate, it will be off by only a couple of mL,
which may change the percents a fractional amount. Still within good working

One word of warning - make certain it is concentrated 40% formaldehyde. If
you start with 10% formalin (4% formaldehyde), and then dilute it another
10%, you will end up with 1% formalin (0.4% formaldehyde), which is next to
worthless for fixing in our rush-rush lab environment.

Also, use unbuffered. If there are buffering salts, the salts will
precipitate out in the alcohol (been there, done that once - whoops).

One other thought - why not use it on both stages of the tissue processor?
Fixes and starts to dehydrate at the same time. Something else to play
around with.

Peggy A. Wenk, HTL(ASCP)SLS
William Beaumont Hospital
Royal Oak, MI 48073

----- Original Message -----
From: <Dorothy.L.Webb <@t> HealthPartners.Com>
To: <histonet <@t> lists.utsouthwestern.edu>
Sent: Friday, October 01, 2004 3:11 PM
Subject: [Histonet] alcoholic formalin

> Would someone please give me the recipe for alcoholic formalin to be used
> the second station of a tissue processor, I believe a 70% mixture?  I
> like to do some experiments with it on one of my processors and I am not
> certain if there are any additives besides formaldehyde and alcohol and to
> what proportions each.  Thanks much!
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