Re: Drierite revisited

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From:Tim Morken <>
Content-Type:text/plain; format=flowed

Gayle wrote:
<I wonder if it is really that important to have absolute 100% alcohol in 
the last station [of the tissue processor].>

Xylene is compatible with one percent water in the alcohol so punctilious 
ETOH is not necessary for processing, although you will have to start with 
that because absolute alcohol is hydroscopic and will absorb water up to 5 
percent if left exposed to the air. The time period it takes to absorb that 
much water is dependent on ambient humidity, temperature, airflow, etc. The 
only way to determine that is to do time period tests with a hydrometer in 
your own lab. For most labs the routine of rotating alcohols every few days 
will ensure adequate "100 percent" alcohol is on the processor.

For drying alcohol in the processor, if you determine it is necessary, 
ceramic molecular sieves are best the job, not Drierite. There was a thread 
on this a few monts ago and a serach of the Histonet Archive would bring 
that up. See:

Tim Morken, B.A., EMT(MSA), HTL(ASCP)
Infectious Disease Pathology
Centers for Disease Control
1600 Clifton Rd.
Atlanta, GA 30333


Phone: (404) 639-3964
FAX:  (404)639-3043

----Original Message Follows----
Subject: Re: Drierite revisited
Date: Wed, 01 Mar 2000 09:11:19 -0500

I was not able to get outside messages for a couple of days, but I did catch
Gayles' response to a question today in regards to Drierite.  Not to go into 
lengthy discussion,  I cut and pasted  a blurp from the previous discussion 
drying agents in tissue processors.

There is no advantage to keeping drierite or any other drying agent in a
processor, Drierite will only hold just so much water and than it becomes
exhausted.  Therefore, there is not any advantage to this practice.

If a problem is occurring in processing, I would suggest changing all 
weekly and bumping the reagents in the middle of the week (this would 
the paraffin baths).

Rande Kline, HT (ASCP)
Technical Services
EM Science/BDH

Gayle Callis <> on 02/25/2000 11:26:07 AM

cc:    (bcc: Rande Kline/EMI/Merck)
Subject:  Drierite

What I have noticed about Dierite is - it tends to crumble into minute
pieces, making a fine dust that I dislike anywhere around my tissues or
tissue sections.
Bet that is a not good for the processor, plus carrys over into all the
rest of the solvents, creating another set of problems, fine grit.

I wonder if it is really that important to have absolute 100% alcohol in
the last station.  I think there has been some recent discussion about
this, and it never seemed to affect my tissues or the way they sectioned
when I used run of the mill 100% ethanol, which is not pure 100% anyway,
more like 98%??? or thereabouts.

Gayle Callis
Veterinary Molecular Biology
Montana State University
Bozeman MT 59717-3610
406 994-4705
406 994-4303

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