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Author: Subject: dcm / methanol /ammonium hydroxide
itsafineday
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[*] posted on 17-12-2019 at 14:29
dcm / methanol /ammonium hydroxide


I am making a solvent with 90% dcm 9% methanol and 1% ammonium hydroxide. I am using dcm from paint stripper. It also contains methanol. I am under the impression that the ammonium and methanol should be mixed before adding to the dcm but I don't know for certain. I currently have azeotropic dcm/methanol.

Can I just mix up the ammonium and the required methanol to bring the dcm/methanol azeotrope to the 90%-9%-1% mix that I am seeking?




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Ubya
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[*] posted on 17-12-2019 at 15:50


sure, do you have 100% ammonium hydroxide?
nope you don't.
are you sure you don't need an ammonia/methanol solution?

ammonium hydroxide is the name given to the acqueous solution of ammonia gas (and it can't be 100%), if your mixture doesn't contain water, you can't use ammonium hydroxide solution, maybe you meant ammonia in methanol





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[*] posted on 17-12-2019 at 16:27


I'm sure the OP is referring to concentrated aqueous ammonia when he says "ammonium hydroxide". It's technically wrong, but even the chemical suppliers call it that.

If you're making 100 mL of this, I'd add 1 mL of aqueous ammonia to 95 mL of you DCM/methanol mixture, and then add more methanol until the solution is homogeneous.

What is the solvent mixture for? Extracting alkaloids from plants?




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itsafineday
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[*] posted on 18-12-2019 at 05:46


Thanks for the clarification, Ubya. I need to check to see if the mixture can contain water.

DA, yeah the solvent mixture is intended to extract amides from plants. It's mainly an exercise to learn some chemistry, though. Thanks for the information. I made the ammonium hydroxide by hydrolizing urea. I followed the Nurdrage video but did two runs on the same water . I had kept the solution very cold and as it warmed it started to boil out the ammonia gas. It noticeably domed the mason jar it was in. I double bagged it and stuck it in the freezer. It was a real eye opener about how easy it can be to underestimate chemicals. I was also very pleased with the effectiveness of my home made fume hood (patting self on back:D).

Would the solution be better if I saturated methanol with ammonia gas for the mixture? I had thought about this but I wasn't sure it was safe and I've been hesitant to ask some questions for worry of being accused of seeking to be spoon fed .




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[*] posted on 18-12-2019 at 08:23


Yes you can make a saturated methanolic ammonia solution and use that in your solvent




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[*] posted on 18-12-2019 at 09:15


The DCM is there to dissolve the plant alkaloids.
The aqueous ammonia is there to make sure that the alkaloids are in their neutral, non-protonated form.
The methanol is there so that the aqueous ammonia mixes with the rest of the solvent mixture, and to make the sure water of the plant juices doesn't separate out into a separate phase.

Using aqueous ammonia is perfectly fine for this extraction. There is no need to muck about trying to make a solution of ammonia in dry methanol.




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[*] posted on 18-12-2019 at 17:23


Yeah, strong aqueous ammonia is what I've seen used for this too.

Some people grind magnesium oxide with the plant material instead of using a basic solvent mixture, but that sounds like a pain to me.

For seeds thorough de-fatting first avoids some nasty emulsions, and if the target material is light sensitive those red bulbs are a good idea if you're not well equipped with tinted glassware.







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