dcm methanol azeotrope???

[metalgirl]

methanol and dcm form an azeotrope, correct? Therefore, a somple distillation of some paint stripper will not seperate the two chemicals, correct?

anyway, a search on the subject has me confused

how can i seperate methanol and dcm?

[indole_amine]

A) several water washes

or

B) several fractional distillations (vigreux-column)


_{indole_amine}

[metalgirl]

water washes....of course......thanks amine
now i guess you need lots of water and lots of shaking

are there any rules of thumb about this?  how much water, shaking and or time is neccesarry to completely remove the methanol?

[hest]

Washing say 1L painstripper with ½L wather for 20sek 3 times will doo the tricek.

[claude]

Beware, certain sort of paint stripper can contain polymers, which are not removed with water washes. They are not a problem, depending what you want to do with your dcm. For a plant extraction for example, I think they will not disturb you, but for a performic oxydation, they could become a problem.

[metalgirl]

the dcm is for percolating the freebase frome a methanol extract of ephedra(dry based) so the methanol must go....talking of polymers, a tin of paint stripper was purchased and it had gone off....the tin was opened to reveal a gelatinous mass that had a smell more noxious than any solvent encountered by swim...felt real bad for an hour at least....so, what the fuck was that shit?
    the tip on polymers is appreciated...the break cleaner with dcm/tce is looking the better choice now....from memory this azeotrope has a nice low boiling point and contains no farting methanol...am off to search on obtaining pure dcm in australia(hint hint......anyone?)

[indole_amine]

I am unsure whether you have distillation equipment (but think so, since you say azeotrope?). But I know that if you do enough water washes (4-5x with equal volume of water), dry with epsom salt and then distill the crude DCM without heating too much, all polymers will stay behind in the distillation flask (usually they are very heavy and have high boiling points) and the receiving flask will contain pure DCM when finished (at least absolutely free from MeOH and polymeric stuff). Absolutely perfect for np Xtractions of dry based pfed, as long as you dry it thoroughly.
(or if you're unsure about possible other ingredoints of your paint stripper, you could also ask nOOdle about OTC DCM sources I think)

TCE is nasty stuff.

Oh, about OTC solvents "gone off": I once bought a bottle of den 95% EtOH that had way too much denaturant in it. Started to clean glassware with it. Just thought "strange, this time it stinks a bit!" at first - and had to quit work an hour later due to severe headache and colleagues complaining about the nasty pungent smell from my lab bench - and not before having disposed off the almost-full bottle as "hazardous organic solvent waste"...    

(never bought that brand again BTW   )


_{indole_amine}