[Nhcoll-l] 70% ETOH in volume?

[Robert Waller]

I wish to bring attention to an unfortunate misunderstanding that has crept into our field, or at least onto this discussion list. That is, thinking that alcohol solutions inevitably separate if left undisturbed.
By definition, true solutions are in their lowest free energy state and cannot spontaneously separate.
This is true for any two substances that remain mutually soluble over any range of temperatures and pressures they might be  exposed to. This is certainly true of ethanol and isopropanol at any combination of temperature and pressure, at least certainly at any human-survivable combination of temperature and pressure.

I suspect most ethanol suppliers would be willing to formulate to any desired percentage and could provide expected specifications for trace constituents of the resulting solution based on analyses of the components. It should not be hard to get cost quotations for that and compare those with in-house mixing costs.
Best,
Rob


From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of Bentley, Andrew Charles
Sent: Wednesday, September 21, 2022 10:10 AM
To: Haff, Tonya (NCMI, Crace) <Tonya.Haff at csiro.au>; nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] 70% ETOH in volume?

Tonya

This is very US centric but I am unaware of any vendor that sells 70% ethanol in large quantities like the 55 gallon drums of 95% ethanol we currently purchase.  Most are molecular grade solutions that are very expensive ($400-1000 for 5 gallons).  I must admit that I have not looked extensively but I would also be leery of pH, additives etc. of any solution that is purchased already mixed.  Solutions like this would inevitably separate if left in storage for any length of time also and would still need to be thoroughly mixed before using I would suspect.

Andy
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Andy Bentley
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From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu>> On Behalf Of Haff, Tonya (NCMI, Crace)
Sent: Tuesday, September 20, 2022 10:01 PM
To: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Subject: [Nhcoll-l] 70% ETOH in volume?

Hello everyone,

Following on our conversation about mixing 70% EtOH, I am wondering if anyone purchases pre-mixed 70% instead of diluting it in-house? We are going through a lot of ethanol right now, and it would ease our work flow if we could cut the in-house mixing stage and just decant 70% straight out of a pre-mixed drum... but I suspect this may come at a cost (and perhaps not only financia?). I would love to hear your thoughts and perspectives on this.

Thanks!

Tonya

-------------------------------------------------
Dr. Tonya M. Haff
Collection Manager
Australian National Wildlife Collection
CSIRO
+61(0)419569109
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