Sciencemadness Discussion Board - Antifreeze in Heating Bath

Antifreeze in Heating Bath

DFliyerz - 21-4-2015 at 06:54

I was thinking about what I could use in a heating/oil bath for distillation, and realized that I have a 10-year-old bottle of antifreeze in my garage. Would it be too dangerous to use due to the methanol content, or could I boil off the methanol and then use the remaining propylene glycol as a high-boiling heating bath medium?

macckone - 21-4-2015 at 10:14

I have used ethylene glycol before (BP 197C). It reeks but it works. Better is corn oil (smoke point 230C) or peanut oil (smoke point 230C). Safflower oil is the highest smoke point food oil (265C).

http://www.seriouseats.com/2014/05/cooking-fats-101-whats-a-...

silicone based dot 5 brake fluid is BP 260C but it smells badly too.

subsecret - 21-4-2015 at 10:19

It would make a nice substitute for an ice bath.

DFliyerz - 21-4-2015 at 12:24

Quote: Originally posted by macckone

I have used ethylene glycol before (BP 197C). It reeks but it works. Better is corn oil (smoke point 230C) or peanut oil (smoke point 230C). Safflower oil is the highest smoke point food oil (265C).

http://www.seriouseats.com/2014/05/cooking-fats-101-whats-a-...

silicone based dot 5 brake fluid is BP 260C but it smells badly too.

Really? I'd think that using ethylene glycol would be odorless, since it's normally odorless.

BromicAcid - 21-4-2015 at 14:38

Never really thought ethylene glycol was odorless, smells sweet to me. The more you heat it, the higher the vapor pressure, the more it is going to smell. On the plus side if you drip water in it, it's not going to spatter at you, on the negative you could readily boil it and ethylene glycol is toxic no matter which route you're taking it in.

DFliyerz - 21-4-2015 at 15:00

Quote: Originally posted by BromicAcid

Never really thought ethylene glycol was odorless, smells sweet to me. The more you heat it, the higher the vapor pressure, the more it is going to smell. On the plus side if you drip water in it, it's not going to spatter at you, on the negative you could readily boil it and ethylene glycol is toxic no matter which route you're taking it in.

Eh, I'll probably just use water for my first distillation, since the compound I'm distilling is volatile.

DFliyerz - 22-4-2015 at 08:16

I just thought I'd post this here because it's somewhat related: I'm planning to distill dichloromethane, but none of the gloves I have nor the funnels I have are resistant to it (funnels are polypropylene and gloves are PVC and nitrile.) How worried should I be about distilling it? And will it destroy the rubber ring on the thermometer attachment of my still head?

Note: I actually have some Teflon tape (I had no idea that plumber's tape was PTFE!), so how should I wrap the still head?

[Edited on 4-22-2015 by DFliyerz]

macckone - 23-4-2015 at 08:08

Unless what you are distilling has some other low boiling point volatiles, you can usually skip the thermometer. DCM will eat up rubber in nothing flat. And it isn't even friendly to viton although viton is good resistance it is effected and will eventually destroy it. One method that is useful is to set
the mixture that contains DCM in a flask in a water bath with the water temperature set half way between DCM and the next most volatile compound (often this is acetone so 16C separation). It will be slow but you can get really good separation and you don't have to worry about the DCM eating through o-rings. For acetone you can bring the temp up to just below acetone's bp. As for a funnel, get a metal one. Most solvent mixtures don't mess up metal. Lacking a source for a good metal funnel, use some aluminum foil. Most cooking stores have stainless steel measurers and funnels.

Thick gloves are going to work best and try not to get any of the solvent on them. Some hardware stores have 'solvent resistant' gloves but they aren't usually very solvent resistant.

Also do this outside as the vapors are mildly hazardous. Not going to kill you immediately and not super carcinogenic but definitely not the best thing to be breathing. Also the smell tends to linger.

PS. If you are boiling gunky mixtures with dissolved solids to extract DCM, use the boil in the can method, then clean up the liquid in glass later.

DFliyerz - 23-4-2015 at 09:34

Quote: Originally posted by macckone

Unless what you are distilling has some other low boiling point volatiles, you can usually skip the thermometer. DCM will eat up rubber in nothing flat. And it isn't even friendly to viton although viton is good resistance it is effected and will eventually destroy it. One method that is useful is to set
the mixture that contains DCM in a flask in a water bath with the water temperature set half way between DCM and the next most volatile compound (often this is acetone so 16C separation). It will be slow but you can get really good separation and you don't have to worry about the DCM eating through o-rings. For acetone you can bring the temp up to just below acetone's bp. As for a funnel, get a metal one. Most solvent mixtures don't mess up metal. Lacking a source for a good metal funnel, use some aluminum foil. Most cooking stores have stainless steel measurers and funnels.

Thick gloves are going to work best and try not to get any of the solvent on them. Some hardware stores have 'solvent resistant' gloves but they aren't usually very solvent resistant.

Also do this outside as the vapors are mildly hazardous. Not going to kill you immediately and not super carcinogenic but definitely not the best thing to be breathing. Also the smell tends to linger.

PS. If you are boiling gunky mixtures with dissolved solids to extract DCM, use the boil in the can method, then clean up the liquid in glass later.

One problem is that my only neck that can connect from a boiling flask to the condenser is a thermometer neck...

macckone - 23-4-2015 at 11:32

See my note about using the boil in the can method.
For the second distillation you could use glass.
If you use the glass, then plug the unused neck.
Aluminum foil will work but will probably also be leaky.
Teflon plumbers tape will also work and if done properly
is less likely to leak. One trick is to find a bolt that fits
fairly closely but not touching your joint. Then wrap the
bolt with teflon tape to seal it so it doesn't come in contact
with your distillate. Finally create multiple layers of teflon
tape to size it to the joint. This uses a lot of teflon tape.
The same trick can be used to mate an undersized joint
into a larger joint. It isn't as efficient as just buying
an adapter but sometimes you need it right now.

Also the plumbers tape may contain lubricants and
other impurities. Baking it in an electric oven at 400F
will help drive those off. Teflon will soften a little at
about 450F and becomes unusable at 500F.

Lambda-Eyde - 25-4-2015 at 02:21

Quote: Originally posted by DFliyerz

One problem is that my only neck that can connect from a boiling flask to the condenser is a thermometer neck...

What do you mean? Can't you just put a glass stopper there? Or do you have a 75 degree distillation adapter with a thermometer adapter at the top instead of a small joint? If so, this is the exact reason you don't buy stuff like that.

Also, buy some glass funnels. That's mandatory equipment in a chemistry lab, IMO. I have 50, 75 and 100 mm standard funnels as well as an 80 mm powder funnel. This selection fulfills most of my needs. The only thing I'm missing is a funnel with a male ground glass joint.

Magpie - 29-1-2016 at 16:59

Quote: Originally posted by macckone

This post made me curious enough to buy a bottle of safflower oil and determine its smoke point. I heated it up to 280°C and it still was not smoking!

My DOT 5 brake fluid silicone oil was smoking at 180°C.

I will continue to use the silicone oil at temperatures below its smoke point due to its inflamability, however.