Sciencemadness Discussion Board - having trouble seperating ether from starting fluid

having trouble seperating ether from starting fluid

LD5050 - 26-3-2017 at 14:09

I'm trying to separate ether from starting fluid. MSDS ingredients say Heptane and Ethyl ether. I tried fractionally distilling I even connected two fractionating columns but I'm not hitting ether bp. The temp stays 18-21c and then goes way over eventually...I can control heat sort of by adjusting hot plate but I cant hit ether bp of 34c... whats going on here?? heptane has a much higher bp but I have heard they are herd to separate from some reason.

Magpie - 26-3-2017 at 14:18

Do the contents include propane and/or CO2?

LD5050 - 26-3-2017 at 15:39

Co2 but isn't that gone once the pressure is relieved from the can?

A Halogenated Substance - 26-3-2017 at 16:03

Quote: Originally posted by LD5050

I have heard they are herd to separate from some reason.

That's because they form an azeotrope.

https://en.wikipedia.org/wiki/Azeotrope
https://en.wikipedia.org/wiki/Azeotrope_tables

The CO₂ shouldn't be a problem unless you don't have adequate cooling upon releasing the ether. The initial release from the can aerosolizes the ether so it can easily escape into the air. (Please correct me if I'm wrong about carbon dioxide's contribution to the problem.)

Magpie - 26-3-2017 at 19:45

I've recovered ether from starting fluid containing CO2 and from SF with propane as the propellant.

It seems that my yields were less with CO2 type as it likely carried off a lot of ether as the CO2 outgassed. But the propane caused low bps when fractionating. It tends to want to stay with the ether distillate. But I got decent yields with both types of SF.

I agree the CO2 should be gone for you. You need a good column (I used a Hempel packed with broken glass) and you need to take it slow, say about 1d/s distillate collection rate.

Make sure your thermometer bulb is correctly positioned in the stillhead.

[Edited on 27-3-2017 by Magpie]

XeonTheMGPony - 27-3-2017 at 05:11

Wrapping cloth loosely over the discharge tube of the ether can helps to coalesce the spray to keep the fine misting down, cotton ball would work well for this.

Putting the collection flask and the can in the freezer over night will greatly help as well (With butane and a deep freezer you can simply cut open the can and pour it in!)

CO2 will dissolve into the into the liquids a bit, but good precooling and slow temp rise will get this out with minimal losses.

Colder you start with and slower you go the better the results, so it really is a test of your patience and self control!

macckone - 27-3-2017 at 09:05

Hints. Put the can in the freezer for an hour before starting.
Same with the collection flask.
Cooling with dry ice can eliminate loss but makes it hard to get out of the can.
Use the vacuum cooling method to distill.
In a sealed system with two flasks, the collection side is cooled with ice water.
The other side does not need heat. If this is done correctly,
You will get ether over but not the other compounds.
Vacuum generally eliminates the azetrope as they exist at specific temp and pressure.
If the source flask is heated before the system is sealed, it
Will flush the air and provide a greater vacuum.

Elemental Phosphorus - 27-3-2017 at 09:07

Does anyone know of a decent way to verify that the ether and heptane fractions of starter fluid are separated?

[Edited on 27-3-2017 by Elemental Phosphorus]

LD5050 - 27-3-2017 at 09:19

I got good results from performing a simple distillation first and collected everything up to 60c then I took everything I collected and fractionally distilled that and got a almost perfect bp of 34c.

Amos - 27-3-2017 at 09:25

Quote: Originally posted by Elemental Phosphorus

Does anyone know of a decent way toverify that the ether and heptane fractions of starter fluid are separated?

The two smells are completely different IMO, but if you're asking for a more scientific way, I don't have much for you. Very small amounts of heptane in your ether shouldn't be a terrible problem though, as it's very unreactive towards just about anything you'd trust ether to solvate. Perhaps someone will tell me I'm wrong and heptane ruins the formation of some complexes or decreases the functionality of a reagent, though.

Texium - 27-3-2017 at 09:49

Quote: Originally posted by macckone

Cooling with dry ice can eliminate loss but makes it hard to get out of the can.

If you cool the can of starting fluid with dry ice, would it then be possible to simply cut open the top of the can since it would no longer be pressurized, and pour out the ether/heptane/CO2 solution into the boiling flask?

Magpie - 27-3-2017 at 11:55

For collection I use len1's method in Prepublication. It works well.

Glad to hear your isolation of the ether worked well. Add some BHT or equivalent if you plan to store it. You can also test it with starch-iodide for peroxide.

Amos - 27-3-2017 at 12:07

Quote: Originally posted by A Halogenated Substance

Quote: Originally posted by LD5050

I have heard they are herd to separate from some reason.

Did anyone else notice that there's no references anywhere to heptane and diethyl ether having an azeotrope?

LD5050 - 28-3-2017 at 15:57

Yes I looked quickly but couldn't find it.

Its strange tho how when I first tried the fractional distillation I couldn't hit ether's bp and I was collecting something mostly at 18c but when I set up for simple distillation and collected every thing up to 60c ( temp instantly went straight to 60c once it started boiling) and fractionally distilled what I collected the first fraction I got was ether's perfect bp..

Texium - 28-3-2017 at 17:46

What most likely happened was that because you were doing a simple distillation, the ether vapor was superheated as it passed over the thermometer due to proximity to the hotplate. Bubbles from under the surface are at a higher pressure and thus a higher temperature even after they break the surface. However, in a fractional distillation since the distillate repeatedly condenses and re-boils as it goes up the column, the vapor passing over the thermometer is right at the actual boiling point.

Not sure if I explained that the best way, but that's the gist of it.

Edit: I usually distill starting fluid directly using a fractional setup and the boiling points are right on.

[Edited on 3-29-2017 by zts16]

macckone - 28-3-2017 at 18:10

Ether will disolve carbon dioxide.
That could account for the low temp.
Bad thermometer placement could also cause issues.
As for dry ice, yes you could cut it open but
Metal can, flammable liquid = potentially dangerous
As for ether azetropes, pentane lowers the bp by 2C
Otherwise, I am not aware of anything at 18C.

Texium - 28-3-2017 at 18:20

Quote: Originally posted by macckone

As for dry ice, yes you could cut it open but
Metal can, flammable liquid = potentially dangerous

Oh right... I guess if you had tin snips or pipe cutters that could cut the can without risk of sparks that could work, but you certainly wouldn't want to use any kind of saw.

macckone - 28-3-2017 at 18:30

They make non-sparking saw blades. But I don't know where to get one.

LD5050 - 29-3-2017 at 06:52

I just hold the can upside down and press the button to release all the pressure or most of it. Then I take something like a sharp screw driver and poke a hole in the top of can which releases the rest of the Co2 and then Ill poke another hole on the top and pour it directly into my boiling flask.

XeonTheMGPony - 29-3-2017 at 11:06

When I was working butane I just punched a hole in the top and a hole in the bottom, gravity does the rest wonderfuly! or some times pipe cutters and remove the top.

Depended on mood.

Tsjerk - 29-3-2017 at 11:46

I think macckone is right about the dissolved CO2 making ether's boiling point lower than expected in the first distillation. This would explain the problem not arising in the second distillation.

Melgar - 29-3-2017 at 14:40

Quote: Originally posted by LD5050

I just hold the can upside down and press the button to release all the pressure or most of it. Then I take something like a sharp screw driver and poke a hole in the top of can which releases the rest of the Co2 and then Ill poke another hole on the top and pour it directly into my boiling flask.

Great minds think alike... or perhaps just lazy ones.