Name: Jennifer J.
I teach 8th grade science, and many experiments in the
book call for the use of ethanol. Can rubbing alcohol be used? If not,
where can I get ethanol?
Pure ethanol is wonderfully versatile: you can use it for
flame heating, cleaning and degreasing, sterilizing, drying out wet things,
dissolving some chemicals water cannot, boiling at a lower temperature
and more other things than I can think up right now.
That is probably why they featured it in your textbook. One simple,
low-toxicity reagent to use for so many things.
You can get it as technical-grade or reagent-grade 100% ethanol from
I'm not sure of the rules, but your being a teacher may make them willing
to send it to you.
Any given thing ethanol does can be substituted by something.
But there are a few different somethings, for different uses.
Learning a little about solvent properties, you can probably pick the
right ones for each experiment.
For burning, standard rubbing alcohol is very marginal, because it's 30%
water, only 70% isopropanol.
You can find 91% isopropanol rubbing alcohol, and that will burn well and
be adequate for some other things.
It's still 9% water, so it won't dry wet things as well as 100% of some
solvent: (ethanol or isopropanol or acetone).
The vapor flammability hazards of 91% isopropyl are a bit less than those
of 100% ethyl alcohol, because the vapor pressure is lower.
70% isopropyl, much lower.
Isopropanol has a higher boiling-point / lower vapor-pressure than
ethanol, methanol, or acetone
so it might not work well in a "drinking bird" thermal apparatus. But you
could try it.
It also does not cool things as aggressively when it evaporates.
You can find denatured ethanols and/or 100% isopropanol in solvent cans at
some paint or hardware stores.
It's 100% solvent and should burn great and extract water thoroughly.
Denaturant additives (~10% concentration) are often like acetone, which
can dissolve many plastics.
There are many plastic things you will not want to wipe down with them or
store them in.
It can ruin a shiny finish, or gradually weaken some plastic containers.
The fumes are a little more unpleasant, too. The flammability risk is a
The price/volume is low in gallon cans.
Anything mixed might not have a single, simple boiling point.
70% rubbing alcohol does. It is an azeotrope: the right percentage
mixture so the water and alcohol boil together at the same time.
So you cannot distill them apart, which is why 70% is the standard
It's a whole 'nuther job for the manufacturer to go to higher percentage.
There is only one azeotropic mix for each pair of solvents,
so the 91% grade of rubbing alcohol will not have a single boiling point.
Instead it will try to evaporate isopropanol vapors and leave 70/30 liquid
behind in the vessel.
30% water is substantial for solvent solubility properties.
There are some greases or waxes that will not dissolve as well in rubbing
alcohol as in pure ethanol.
And it can take a little longer for rubbing alcohol to dry than pure ethanol.
People do use ultra-distilled vodka (ethanol with as little as 10% water)
for some things.
More often, I use rubbing alcohol, 70% or 91% as needed.
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Update: June 2012