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Author: Subject: Methylamine/Ammonia, how to tell them apart?
stoichiometric_steve
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[*] posted on 8-10-2008 at 12:10
Methylamine/Ammonia, how to tell them apart?


i recently bought a bottle of commercial 40% Methylamine solution in Methanol. Now after opening, it struck me that what i may have here is in fact a solution of Ammonia in Methanol, because the smell is so much different than the rotten pussy stench i was used to from the aqueous solutions of methylamine.

is there a quick qualitative test to discern between ammonia and methylamine that could be used to determine if the supplier delivered a mislabeled bottle?




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panziandi
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[*] posted on 8-10-2008 at 12:21


boiling point? methylamine b.p -6*C ammonia b.p -33*C ... should be easy to tell if you pass the vapours through a cold trap whether it is one or the other if you know the temperature of the cold trap would only allow methylamine to condense.



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Klute
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[*] posted on 8-10-2008 at 12:30


Mayeb you could try acidifying an small aliquot, evaporate the methanol, and test the solubility in IPA?



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[*] posted on 8-10-2008 at 14:22


Flame test; methylamine is much easier to ignite than ammonia (it has lower and wider flammability limits). If you want to get tricky pass combustion product through milk of lime to test for CO2 which ammonia of course will not produce.



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[*] posted on 8-10-2008 at 16:52


Quote:
Originally posted by stoichiometric_steve
i recently bought a bottle of commercial 40% Methylamine solution in Methanol. Now after opening, it struck me that what i may have here is in fact a solution of Ammonia in Methanol, because the smell is so much different than the rotten pussy stench i was used to from the aqueous solutions of methylamine.

is there a quick qualitative test to discern between ammonia and methylamine that could be used to determine if the supplier delivered a mislabeled bottle?


Just run it past the g/f!
Does this smell like rotten pussy?
Reckon on a substantial loss of china and glass plus cases being packed and a decampment to her mother's for a few weeks :(
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JohnWW
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[*] posted on 8-10-2008 at 17:31


CH3-NH2 would have a C-N bond, with the C and N bonded only to Hs, unlike CH3OH and NH3. So, if you have a scanning infrared spectrometer, a C-N absorption band would show up if any CH3NH2 is present, and the wavelength would be at the short end of the IR absorption of C-N bonds.
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not_important
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[*] posted on 8-10-2008 at 20:01


How about sacrificing a few cc to make the hydrochloride, then evaporate to dryness. From The British Pharmaceutical Codex

Quote:
METHYLAMINE HYDROCHLORIDUM.
METHYLAMINE HYDROCHLORIDE.
CH6NCl = 67-508.

Methylamine hydrochloride, CH3NH2,HCl, is prepared by neutralising an aqueous solution of methylamine with hydrochloric acid, and evaporating to dryness. The residue dissolves readily in boiling alcohol, which, on cooling, deposits the salt in crystals. These crystals at the moment of their formation appear iridescent by reflected light.

It occurs in fine, large laminae, colourless, and deliquescent. Very soluble in water and in alcohol ; insoluble in chloroform. Its solubility in alcohol distinguishes it from ammonium chloride. Melting-point, 222°. Heated in an open vessel to a high temperature, it volatilises in dense vapours, which condense to a white powder on cold surfaces. It forms with many metallic chlorides well- crystallised double salts.



From the OrgSynth entry, 800-900 g of dry MeHH3Cl should dissolve in 2 liters of boiling absolute ethanol. It will be a somewhat less soluble in isopropanol, but not more than half as much, and ammonium chloride is nearly total insoluble in i-PrOH.

Also https://sciencemadness.org/talk/viewthread.php?goto=lastpost...

[Edited on 9-10-2008 by not_important]

NH4Cl_solubility.png - 15kB
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chemrox
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[*] posted on 8-10-2008 at 22:37


pure meam smells a lot like ammonia but I like the suggestion to employ a few drops of HCl on a small sample. The crystals are shinier and more platelike than NH4Cl. Very hygroscopic .. in a humid atmosphere they will disappear in a puddle. And then you can always do phys. props. of the sample.



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[*] posted on 9-10-2008 at 16:18


i don't believe a 40% solution in methanol is possible either for methyl amine or ammonia. Who did you buy it off, www.iamdodgeychemsupplier.com?

40% MeAm in H20, the highest possible at STP has a bp of 48C.

[Edited on 9-10-2008 by Panache]




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[*] posted on 9-10-2008 at 23:13


Quote:
Originally posted by Panache
i don't believe a 40% solution in methanol is possible either for methyl amine or ammonia. Who did you buy it off, www.iamdodgeychemsupplier.com?

So you consider Abcr, one of the biggest chemical suppliers in Europe, a bit dodgy to offer 40% methylamine solution in methanol for sale:
http://shop.abcr.de/product_information.aspx?product_id=3504...

(There are a few other small suppliers that also sell it. It is however true that Sigma does not, but they do sell 33% solution in ethanol.)




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stoichiometric_steve
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[*] posted on 10-10-2008 at 00:27


The stuff i have is from TCI Tokyo Kasei (cheapest supplier for this item that i know of, 26 EUR per 500ml vs. 79 per 100ml from ABCR). I have now put some HCl in IPA on a few drops of the methanolic solution and it turns out the stuff is indeed very deliquescent, as opposed to a sample of NH4Cl.

It is peculiar that the smell of methylamine obviously depends very much on solvate molecules. Alternatively, the 40% aq. solution i have (from Acros) may be contaminated with traces of dimethylamine that cause the pussy smell. It really makes me sick to smell the aqueous stuff, while the methanolic solution doesn't bother me nearly as much...

[Edited on 10-10-2008 by stoichiometric_steve]

[Edited on 10-10-2008 by stoichiometric_steve]




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[*] posted on 10-10-2008 at 03:56


heat some of the solution and drip hcl into it. if you get a white fluffy percipitate you have ammonia piss easy

the smell is normal for nitromethane being reduced in alcohol the fish smell telling the chemist of the existence of excess water.


[Edited on 10-10-2008 by Ephoton]




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stoichiometric_steve
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[*] posted on 10-10-2008 at 06:13


yeah i get it now, close the thread



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Panache
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[*] posted on 10-10-2008 at 06:46


Quote:
Originally posted by Nicodem
Quote:
Originally posted by Panache
i don't believe a 40% solution in methanol is possible either for methyl amine or ammonia. Who did you buy it off, www.iamdodgeychemsupplier.com?

So you consider Abcr, one of the biggest chemical suppliers in Europe, a bit dodgy to offer 40% methylamine solution in methanol for sale:
http://shop.abcr.de/product_information.aspx?product_id=3504...

(There are a few other small suppliers that also sell it. It is however true that Sigma does not, but they do sell 33% solution in ethanol.)


hmmm, perhaps i should have checked other sources beyond the Sigma catalogue in front of me. Apologies all, the dodgey comment pertained to the fact that steve seemed to think his company had such poor systems they could mislabel one item as another but written after my questioning whether such a product was even possible implied that it was their marketing that was dodgy.
Basically a useless post on all front.
Apologies.




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Klute
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[*] posted on 10-10-2008 at 07:08


Mislabeled products are not that uncommon, even with leading products. Especially with products that look alike. The problem doesn't come from the production obviously, but the labelling of the bottles. Out of all the mislabled items, some of them get through the checkups and are then sent away. Sometimes you get lucky, other times you don't!



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stoichiometric_steve
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[*] posted on 10-10-2008 at 08:02


yeah but GUYS, it's already cleared up, thanks!



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