<div dir="auto">Thank you Dirk, very helpful! </div><div style="line-height:1.5"><br><br>-------- Ursprüngliche Nachricht --------<br>Von: Dirk Neumann <d.neumann@leibniz-lib.de><br>Datum: Do., 17. Nov. 2022, 08:33<br>An: nhcoll-l@mailman.yale.edu<br>Betreff: Re: [Nhcoll-l] Bouin's formula<br><blockquote><div>
<div>Hi Tonya,</div>
<div><br />
</div>
<div>Simon's and Paul's recommendation are straight forward, and we have to assume that specimens in Bouin's are present in many collections. They are usually very easy to spot because of the intense and bright light yellow colour of
the fluid, which also stains the alcohol after the transfer of the specimens.</div>
<div><br />
</div>
<div>Often these specimens entered collections as research specimens after taking histological samples from those vouchers, therefore, they often are not stored in qualitatively high and especially tight closing jars we normally would
use for storage of specimens. Thus transferring them to better jars is an option to stabilise them, but if you know that you have Bouin-preserved specimens in your collection, it is useful to know where these jars are and to have a closer monitoring for those
jars in the collection. Often, the volume of the jars is less then 50 ml and thus these jars have a higher risk to dry up unnoticed.</div>
<div><br />
</div>
<div>Bouin's is a water-based acidic fixative, often leading to considerable shrinkage of tissues and of course loss of calcium carbonate from bones. If they are no longer needed or wanted for histology and should be transferred into
alcohol, you would like to avoid rinsing them in water and exposing them for too long in low concentrated alcohol. In Fact - at least for larger and specimens with a more stable tissue matrix - it might be better not to step but to transfer them into 50% EtOH
or even higher. A key factor here is the question how stable the tissues and tissue membranes are to withstand this sudden osmotic shock (as this more or less direct transfer extracts water from the cells, of course), or, vice versa, how damaged tissues and
membranes are after prolonged exposure in an highly acidic storage fluid.</div>
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<div>Usually, after the transfer into alcohol, more picric acid escapes from the specimens, which you can easily notice because of the vivid yellow staining of the alcohol. As we have to assume that this has an effect on the pH equilibrium
(without wanting to dive into the details of "measuring pH in alcohols" here), it is worth considering to exchange the alcohol after some time has lapsed again. Time intervals depend on common factors as 'number of specimens', 'volume of the container', 'osmotic
pressure', etc. My rule of thumb was if I could notice a considerable yellow stain after transfer, I would exchange the alcohol again.
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<div>Again and as often, not a clear cut answer, but hopefully somewhat useful.</div>
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<div>With best wishes</div>
<div>Dirk<br />
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<div>Am 17.11.2022 um 01:58 schrieb Simon Moore:<br />
</div>
<blockquote>
<pre>Hi Tonya,
I used to deal with Bouin’s fluid back in my histology days. The only slight risk is if the picric acid content has dried to yellow crystals and you have screw top jars. The picric acid is a tri-nitrate so yes, it’s unstable and might spark a bit in this situation. If this is so, then immerse the jars in cold water so that the picric acid goes back into solution and is then quite safe. I have had dry picric acid situations like this before and this method has always worked well and no fireworks!
With all good wishes, Simon
Simon Moore MIScT, RSci, FLS, ACR
Conservator of Natural Sciences and Cutlery Historian,
<a href="http://www.natural-history-conservation.com">www.natural-history-conservation.com</a>
</pre>
<blockquote>
<pre>On 16 Nov 2022, at 23:31, Haff, Tonya (NCMI, Crace) <a href="mailto:Tonya.Haff@csiro.au"><Tonya.Haff@csiro.au></a> wrote:
Hello all,
We have quite a few specimens (mostly macropod pouch young, turtle embryos and turtle organs) that have been preserved in Bouin’s formula, which contains picric acid. I know that picric acid is explosive on impact, and so we are wary of the potential risk that the jars of those specimens may pose. However, I don’t have any real understanding of what the actual risk of explosion might be… should these specimens and their jars be disposed of because opening them poses too much of a risk, or are the levels of picric acid so insignificant as to not pose a risk? Or is there some halfway point, but a way of safely opening the jars without calling the bomb squad? If any of you have thoughts or experience with this I would really appreciate it!
Cheers,
Tonya
-------------------------------------------------
Dr. Tonya M. Haff
Collection Manager
Australian National Wildlife Collection
CSIRO
+61(0)419569109
<a href="https://www.csiro.au/en/about/facilities-collections/collections/anwc">https://www.csiro.au/en/about/facilities-collections/collections/anwc</a>
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NHCOLL-L is brought to you by the Society for the Preservation of
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