[RabidTurkey]

Hello! Sorry if this is in the wrong place, I have put it here as it involves Methanol and Ethanol, but mods feel free to move it if I am stupid. Also it has been a few years since my chemistry classes, so I apologize in advance for sounding fairly inexperienced here!

I have a mixture that involves a small amount of solutes all of unknown concentration, including Water (H20), Methanol (possibly), Ethanol, and other minor materials (including sugar).

My questions are:

1) Is there any test that can be preformed to test for the presence of Methanol, without giving a false positive from ethanol? I assume I can boil off vapor and collect Methanol and Ethanol, and use that cooled back down to liquid form and preform a test, but any info on a test is good.

2) I am not concerned about the amount of methanol, merely I need to know that there is as little of it as possible. Therefore, just like boiling pure, distilled water to test if there is salt in it (which there should not be), I need a way to make sure that there is none. - - - I notice that Methanol has a Boiling point under standard conditions of 64.7 °C, and ethanol of 78.4 °C. While I am probably forgetting a rule or law regarding liquids and mixtures and Boiling Points, would it be possible to, say, boil this solution to 70°C, evaporate any Methanol but leave the Ethanol?

[nj_bartel]

I'm blanking out on the term.... but alcohols form complexes with water in a way that alters the boiling point of the overall solution.  I'm not sure what effect a mixture of 2 alcohols with water would have on the overall boiling point.

[agrobert]

How about 3A molecular sieves?

[macman104]

I'm blanking out on the term.... but alcohols form complexes with water in a way that alters the boiling point of the overall solution.  I'm not sure what effect a mixture of 2 alcohols with water would have on the overall boiling point.

Azeotrope

[nj_bartel]

Thank you!  Hate the tip-of-the-tongue feeling.

[Arkcon]

You may be able to fractionally distill a water-methanol-ethanol solution.  Yes, you will get azeotropes with these component.  But these azeotropes, and their compositions, and their boiling points are published, I'd send you to the CRC, but there may be other printed references.

I don't know if you can prove your composition adequately with fractional distillation.  It will depend on the volume of sample you have, and the volume you distillation rig can work with.

You can also use a gas chromatograph, it can give precise and accurate results for a water-ethanol-methanol mixture.  And many local labs have them.

[Arkcon]

A lady at work told me a story.  It seems her sister works for a small provicial government agency in mainland China.  The story goes that, deep in a rural area, after a wedding, a bunch of people died, and some others were sticken blind, with other neurological damage.  The obvious conclusion, the wine was spiked with methanol. 

So she begins to pack up her portable GC into an all terrain vehicle, for the conclusive proof.  Then the message comes, in the interim, they had a funeral for the dead, and, well, post funeral, more people died, and were blinded.  My colleague's sister then sputters, "Can they please stop celebrating just long enough for me to get there and check what batches they can and can't celebrate with?"

My major point in bringing this up is, no matter where in the world you are, there is a gas chromatograph, ready to analyze something for methanol-ethanol and other volatile solvent content.  No matter how remote the area, or poor the country.  (Yeah, China's hardly poor, or non-technical, but it is large, and rural areas can be quite remote.)

[7453K]

whats an azeotrope?