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Grain Alcohol
What Is Grain Alcohol and How Is It Used
in Spirits?
by Anne Marie
Helmenstine, Ph.D.
Grain alcohol is a purified form of ethyl alcohol (ethanol) made
from the distillation of fermented grain.
The ethanol is produced via fermentation of sugars in the
grain by yeast prior to repeated distillation or rectification.
The term "grain alcohol" may be used to refer to any ethanol
produced from grain or another agricultural origin (as in beer or vodka) or it
may be reserved to describe alcohol that is at least 90% pure (e.g.,
Everclear).
Grain alcohol is a colorless liquid with the chemical formula C2H5OH or C2H6O.
Grain alcohol is considered a "neutral spirit," meaning it
has no added flavor.
Most people would say purified alcohol has a medicinal flavor and a
slightly chemical odor. It is flammable and volatile.
Grain alcohol is a central nervous system depressant and
neurotoxin.
Ethanol is the type of alcohol found in alcoholic
beverages and used as a recreational drug, but it is also used as a solvent,
antiseptic, fuel, and in various industrial applications.
Also Known As: Everclear (brand name), Century (brand name), Gem Clear
(brand name), pure alcohol, absolute alcohol, EtOH, pure grain alcohol (PGA),
pure neutral spirits (PNS), rectified spirit, rectified alcohol
Why Grain Alcohol Isn't 100 Percent Pure
Grain alcohol is commonly bottled at 151-proof (75.5 percent alcohol
by volume or ABV) and 190-proof (95 percent ABV or about 92.4 percent ethanol
by weight).
The 190-proof version is prohibited in many U.S. states and other
locations because it's considered too easy for people to get alcohol poisoning
using the product.
There is no 200-proof (100 percent ABV) grain alcohol for human consumption
because of azeotropic effects during the distillation process.
Fractional distillation can only concentrate ethanol at a ratio of 96
alcohol to 4 water, by weight.
To further purify ethanol from grain alcohol or another source, it's
necessary to add an entraining agent, such as benzene, heptane, or cyclohexane.
The addition forms a new azeotrope that has a lower boiling point and
is made of ethyl alcohol, water, and the entraining agent.
Water-free ethanol may be obtained by removing the lower-boiling
azeotrope, but contamination by the entraining agent makes the alcohol unfit
for human consumption (not to mention, pure alcohol is of itself highly toxic).
At lower pressures (less than 70 torr or 9.3 kPa), there isn't an
azeotrope and it's possible to distill absolute alcohol from an ethanol-water
mixture.
However, this procedure (vacuum distillation) is not presently
economically viable.
Of course, grain alcohol may be further purified by simply adding
a desiccant or using a molecular sieve to
remove the water.
Grain Alcohol and Gluten
There is some disagreement about whether or not grain alcohol, under
any definition, causes problems for people with celiac disease or gluten
sensitivity.
From a chemical standpoint, whiskey (usually made from rye), vodka
(usually made with wheat), and Everclear (typically made from corn) do not
contain gluten because of the distillation process.
Yet, there are reports of people experiencing problems.
When a reaction occurs, it could result from contamination at the
processing facility or because a grain product was added back into the product.
The gluten zein in corn is typically well-tolerated by people with
celiac disease, so grain alcohol from that source should be fine.
Alcohol from another source, such as grapes or potatoes, presents
another option.
Anne Marie Helmenstine, Ph.D.
Ph.D. in biomedical sciences from the
University of Tennessee at Knoxville - Oak Ridge National Laboratory.
Science educator with experience
teaching chemistry, biology, astronomy, and physics at the high school,
college, and graduate levels.
ThoughtCo and About Education chemistry
expert since 2001.
Widely-published graphic artist, responsible
for printable periodic tables and other illustrations used in science.
Experience
Anne Helmenstine, Ph.D. has covered
chemistry for ThoughtCo and About Education since 2001, and other sciences
since 2013. She taught chemistry, biology, astronomy, and physics at the high
school, college, and graduate levels. She has worked as a research
scientist and also abstracting and indexing diverse scientific literature for
the Department of Energy.
In addition to her work as a science writer,
Dr. Helmenstine currently serves as a scientific consultant, specializing in
problems requiring an interdisciplinary approach. Previously, she worked
as a research scientist and college professor.
Education
Dr. Helmenstine holds a Ph.D. in biomedical
sciences from the University of Tennessee at Knoxville and a B.A.
in physics and mathematics with a minor in chemistry from Hastings
College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive
chemical detection and medical diagnostic tests.
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