petertohen - 12-10-2017 at 20:09
There was a thread on this topic from like 2011, but I figured I would start up a new thread anyway.
So I am purifying 70% ethanol from the drugstore. I first did a simple distillation to collect a distillate of about 90% ethanol (determined by
measuring density), with the balance being acetone and water. I then dried the mixture with MgSO4 to remove the water, and setup for fractional
distillation to remove the acetone.
Since acetone is a denaturant, it was probably only 5% of the solution.
My fractionating column is just a plain-old tube, so I added steel wool to allow sites for fractionation to occur. On my first distillation, I used
way too much wool and it basically became a reflux condenser (no distillate came over).
On my second try, I used a lot less wool and did get a distillate, but it came over at 46 Celsius!!
Of course, ethanol boils at 78.4 and acetone boils at 56. An ethanol-water azeotrope (which shouldn't form anyway since it was dried prior to
distilling) boils at 78.2, and no azeotrope exists between acetone and water OR between acetone and ethanol (correct me if I'm wrong).
The thermometer was in the right position. About 2-3 degrees can be explained by a drop of liquid condensing on the thermometer, and another 3-4
degrees can be explained by the innacuracy of the thermometer (an EtOH-water azeotrope on my first distillation came over at 82 deg. instead of the
expected 78 deg.).
But still, 10 degrees off of the boiling point of acetone (which should be what came over) does seem a little outrageous.
I stopped the distillation short (today I will run it and see if the vapor temp ever rises above 46 celsius).
I have yet to test the 46 degree distillate with dichromate to see if it contains any ethanol.
Has anyone ever had a similar thermometer problem like this? Can the 10 degree error be accredited to the sources I mentioned above, or is there
something really wrong with my procedure?
Thanks for any input!
http://www.sciencemadness.org/smwiki/index.php/Main_Page
Vosoryx - 12-10-2017 at 20:44
What type of thermometer?
If you were using a chemical thermometer like an alcohol or mercury one, that seems a bit strange. If you were using a thermocouple, there could be
issues with the probe/reader.
I don't know enough about the chemistry to tell you what other compounds could exist in your mixture, but I think you're right about the azeotropes.
wg48 - 13-10-2017 at 00:38
Why not check the thermometer’s calibration by distilling water and preferably also with a pure ice and water mixture for a two-point calibration?
Also correct for air pressure (boiling point) for better accuracy?
Why do you think condensation on the thermometer produces errors? The set up should be actively refluxing so there should be condensation on the
thermometer.
Here is a link to a procedure: http://immaculatebrewery.com/temperature-calibration/
[Edited on 13-10-2017 by wg48]
XeonTheMGPony - 13-10-2017 at 03:36
All so check your altitude as higher up you are the colder some thing will boil.
AvBaeyer - 13-10-2017 at 19:24
I had a problem where a distillate was coming over well below the expected boiling point. It turned out that I was not paying attention and the
thermometer was not inserted deep enough into the still head. Make sure the bulb of your thermometer is below the point where the vapor enters the
condenser.
AvB
Melgar - 16-10-2017 at 06:27
They never list all the ingredients on denatured alcohol. There are always at least three that are neither on the label nor in the MSDS, and they're
always selected based on the likelihood that they'll make your life more difficult. What does it smell like? Just acetone? If so, the mystery
component may be n-hexane, which forms an azeotrope with acetone at 49C.
[Edited on 10/16/17 by Melgar]
zed - 4-11-2017 at 14:42
Ummm. This denatured Ethanol mixture was formulated to be difficult to refine.
Start with something else.
I personally, am offended at paying recreational beverage prices for Ethanol, which I intend to use for industrial purposes. But, the U.S.
Government is adamant about collecting the beverage tax. AND, most of the guys that sell anhydrous, won't sell to you, unless you have the tax-free
permit; they don't want the burden of collecting the tax. When you obtain the tax free permit, it comes with a supervising ATF agent. A situation,
which of course, you want to avoid.
Everclear is about 10-15 bucks a liter hereabouts, and it contains only Ethanol 95% and H2O. The beverage tax, is included in the price. The tax
stamp should be on the bottle. Since the tax has already been paid, the possibility of later legal difficulties is avoided.