stoichiometric_steve
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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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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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Mayeb you could try acidifying an small aliquot, evaporate the methanol, and test the solubility in IPA?
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smuv
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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.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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ScienceSquirrel
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| 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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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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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.
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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]
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chemrox
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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.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Panache
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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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Nicodem
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| 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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Read the The ScienceMadness Guidelines!
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stoichiometric_steve
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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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Ephoton
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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]
e3500 console login: root
bash-2.05#
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stoichiometric_steve
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yeah i get it now, close the thread
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Panache
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| 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.)
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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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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!
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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stoichiometric_steve
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yeah but GUYS, it's already cleared up, thanks!
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