Research Notes:
Isopropyl vs Ethyl alcohol
The highest proof alcohol you can buy is Everclear, at 190 proof. That’s nothing! Let’s get together and make an alcohol that’s 200 proof! Except we can’t possibly do that. There’s a physical limit to how pure alcohol can actually get, and we’ll tell you why.
Ethanol, the business molecule of alcohol, is more volatile than water. Given any set of conditions, it will be more likely to fly away than water molecules. This includes higher temperatures. Heat up a mix of ethanol and water, and more of the ethanol will go away. This proved a bane to liquor makers, until someone stumbled on the secret of distillation. Heat up a mixture of ethanol and water to a point where the alcohol boils but the water (except for the stray molecule or two) does not, and you can make a liquid that’s pure water and collect a steam that’s pure ethanol.
Few people actually wanted pure ethanol, though. Though a little extra kick was good, only the hardcore drinkers demanded pure alcohol — and they weren’t going to be repeat customers. So it took a relatively long time for people to realize that no one could make pure alcohol or pure water from ethanol and water.
This is because ethanol is not an ordinary mixture, it’s an azeotrope. Instead of boiling purely and separately at two different temperatures, its vapor will form a certain proportion. Steam from alcohol is 95.57 percent alcohol. Get a pot of 95.57 percent ethanol boiling and the steam will be 95.57 percent ethanol right down until the last drop evaporates. That’s the limit.
It seems like it should be enough. (There is, reportedly a Bolivian beverage,
Cocoroco, that’s 96 percent ethanol. It’s not legal, but it does exist.) However, leave it to people to try and change it. Someone found a solution. Benzene, when added to a mixture of water and ethanol, will allow more alcohol to steam upwards. What a disappointment that benzene was found to be carcinogenic. Well, we still can dream.
[Source:
Solvent Recycling,
Proof: The Science of Booze by Adam Rogers.]
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I was reading that ethanol can only be purified up to something like 95% by distillation and further purification calls for CaO. Why is this? Is CaO a drying agent? Why is it that you can't separate water completely from ethanol? Is it just not feasible without CaO, like the tiny amount of water is nearly impossible to remove due to their being so much ethanol around it. Their structures are similar, they both are polar with the OH group and there are few carbons on the ethanol so they are pretty miscible (sp?). So I guess I can see how water would have trouble breaking free of its bond to ethanol in solution, at such a low concentration. I can see it, but is it right?
At the concentration of 95% ethanol, water and ethanol form what is known as an azeotrope. This is a mixture in which the azeotrope distills off before the desired liquie (ethanol). Citing from my memory, ethanol boils at 78.3C and the azeotrope of 95% ethanol/water boils off at 78.15C. So you really neevr can get 100% ethanol from distillation because the azeotrope has a lower boiling point and so you have to use a dehydrating salt (CaO).
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Isopropyl vs Ethyl alcohol facts:
Ethyl alcohol consists of 2 carbon atoms while
isopropyl alcohol has 3 carbon atoms.
Ethyl alcohol is produced when ethene is hydrated or when sugar is fermented by yeast cells. ...
Ethyl alcohol is suitable for drinking while
isopropyl is toxic when ingested. Both can be used as a cleaning agent
Isopropyl alcohol, often called IPA or
isopropanol, is similar in function and structure to
ethanol. It evaporates at a similar rate and destroys bacterial and viral cells by the same mechanism. However, it is not as effective at dehydrating living tissue and so is a
better solution for disinfecting skin
than ethanol
Fuel grade
ethanol may contain dangerous impurities and should never be consumed.
Ethanol (C2H6O), the alcohol in alcohol beverages, sometimes just called “alcohol.” ... However, it is toxic to
drink. Methanol (CH3OH), sometimes called “wood alcohol,” is highly toxic.
Ethanol, or
ethyl alcohol, is the only type of
alcohol that you can
drink without seriously harming yourself, and then only if it hasn't been denatured or doesn't contain toxic impurities.
Ethanol is sometimes called grain
alcohol because it is the main type of
alcohol produced by grain fermentation.
If as little as 10 ml of pure
methanol is ingested, for example, it
can break down into formic acid, which
can cause permanent blindness by destruction of the optic nerve, and 30 ml is potentially fatal, although the median lethal dose is typically 100 ml (3.4 fl oz) (i.e. 1–2 ml/kg body weight of pure
methanol).
EFFECTS OF SHORT-TERM (LESS THAN 8-HOURS) EXPOSURE:
Methanol's toxicity is due to its metabolic products. The by-products of
methanol metabolism
cause an accumulation of acid in the blood (metabolic acidosis),
blindness, and death.
Source
https://www.physicsforums.com/threads/the-problems-with-100-pure-ethanol.12847/
I hope this helps someone else improve their understanding of the differences. These articles have certainly given me something to think about and seriously consider. Before all i had were myths; these seem based on solid science. Science that I can live with.