[Nhcoll-l] Mixing EtOH

[Callomon,Paul]

We cut 95% ethanol to 80% in 25-liter carboys, rolling them on their sides to mix. I regularly test the fluid during use, and it holds steady at 80-81% (I just tested the remains of a batch mixed in March; 80.6 originally, 81.0 now in a sample drawn through the spigot; presumably slightly lower at the surface). I haven't, therefore, seen major re-separation, though I'm aware (thanks to John's work!) of the properties of binary azeotropes. Could it be, I wonder, that the slightly higher concentration we use helps avoid this problem? We switched from 70% to 80% about 20 years ago.


Paul Callomon
Collection Manager, Malacology and General Invertebrates
________________________________
Academy of Natural Sciences of Drexel University
1900 Benjamin Franklin Parkway, Philadelphia PA 19103-1195, USA
prc44 at drexel.edu<mailto:prc44 at drexel.edu> Tel 215-405-5096 - Fax 215-299-1170



From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of Haff, Tonya (NCMI, Crace)
Sent: Tuesday, September 6, 2022 9:40 PM
To: nhcoll-l at mailman.yale.edu
Subject: [Nhcoll-l] Mixing EtOH


External.
Hello all,

I have a question about mixing storage strength (70%) undenatured EtOH. Typically we add the correct proportions of 95% EtOH and water to a container and paddle or invert the container repeatedly to mix the liquids, and allow it to sit for ~24+ hrs. The containers we like best to use for dispensing 70% EtOH are 20L plastic water containers with a tap at the bottom. Recently we used our digital alcohol meter to test the alcohol concentration from the top and bottom (tap) of one of these containers and found the alcohol concentrations wildly different  - ~80% at the top and ~60% at the bottom - despite having been mixed more than 24 hours earlier. This makes me really concerned that we could be regularly using concentrations that are much above 70% with specimens. I wonder if any of you have had a similar problem, or if anyone can suggest a solution? Is there a better way of mixing or of ensuring the solution is properly combined? Any thoughts appreciated.


Thank you!

Cheers,

Tonya
-------------------------------------------------
Dr. Tonya M. Haff
Collection Manager
Australian National Wildlife Collection
CSIRO
+61(0)419569109
https://www.csiro.au/en/about/facilities-collections/collections/anwc<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.csiro.au%2Fen%2Fabout%2Ffacilities-collections%2Fcollections%2Fanwc&data=05%7C01%7Cprc44%40drexel.edu%7Cd03592d84dd74241473408da9071dc8a%7C3664e6fa47bd45a696708c4f080f8ca6%7C0%7C0%7C637981115973263441%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=K%2F95ao2%2FCHvq5tt%2FfPjFqZ0ORcgpA8z54x3HB1fI284%3D&reserved=0>

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