Ask A Scientist Chemistry Archive

name         Javier A.
status       educator
age          20s

Question -   Hi !!
Why does the Glacial Acetic Acid is called like that? (The GLACIAL terminology is the 
problem.)
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This is a quote from the referenced web site below.  It could be fact or fiction.  I do 
not know.  But I always wondered that too so here is our answer.  Everything in quotes 
below was a direct copy from the URL below:


"Synthesis:    Acetic acid is available as an OTC chemical in the form of vinegar, a 
dilute solution of acetic acid. Vinegar should be available from any grocery story in 
3%-5% concentrations or so. Acetic acid is a chemical that I consider to plentiful to 
bother synthesizing yourself since it is a cheap, abundant OTC chemical. It can be done, 
and it may be cheaper in the long run to make it on your own, but I do not have the 
information handy. A trip to the library, or a web search will yield much info on the 
topic. Acetic acid is more useful in concentrated, or glacial, form. Only acetic acid is 
referred to as glacial rather than concentrated acid. This is because the ancients liked 
how much frozen acetic acid looked, it reminded them of an ice glacier, so the term 
glacial stuck. Glacial acetic acid is very corrosive and slightly flammable."

http://roguesci.org/megalomania/synth/synthesis1.html

** Scroll down to 'acetic acid' **

Regards,
Darin Wagner
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Javier,

(Glacial) 99.8 % minimum acetic acid has a rather high freezing point ==> 16.6 C. When 
frozen, it looks quite like ice crystals. Thus, the term, "glacial."

Regards,
ProfHoff 692
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Javier,

Pure 100% acetic acid is sometimes called glacial acetic because when cold, it will 
solidify into layered crystals similar in appearance to a glacier.  I hope this answers 
your question.

Sincerely,

Bob Trach
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Good question, I do not really know.  But 100% acetic acid melts at 16.7 C = 62 F. I 
suspect that once upon a time when labs were not well heated that acetic acid crystallized 
when the temperature was low. Acetic anhydride melts at -73 C. Since the freezing point of 
water is 0 C. then slightly "wet" pure acetic acid would crystallize the pure acetic acid 
(i.e. "glacial" acetic)
leaving the water in the liquid phase or the acetic anhydride also in the liquid phase. If 
the crystallized acetic were separated from the liquid it would be purified. So I am 
guessing the tag "glacial" referred to acetic acid that had been purified of residual water 
or acetic anhydride.

Vince Calder
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