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Db33
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how to get make a nitrogen atmosphere?
There is a reaction i want to do, everything about the reaction seems doable and quite easy except it says the reaction was stirred under nitrogen for
a few hours.
Now in a good lab i know they have tanks with nitrogen and they have very easy to use pieces that make it easy to take some of that and fill a balloon
and then use that for the vessel.
But for someone without a sophisticated lab just using household items. How can this be done?
i know Amazon sells these
https://www.amazon.com/Disposable-Tank-of-Nitrogen-Filled/dp/B013KC9FUK/ref=sr_1_1?ie=UTF8&qid=1488652720&sr=8-1&keywords=nitrogen
but how do i get this into a flask to flush it and keep it under nitrogen?
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AJKOER
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One could try placing a dish of fine iron particles, sprayed with a fine mist of an acid (like lemon juice) with added NaCl, floating on water in a
vessel half full of air. If you arrange it so that the dish is floating in an inverted jar of air/H2O, you can see if the O2 is being consumed.
An alternate related reaction would be an acid mist applied to Cu2O (in place of iron) and a touch of sea salt.
The idea stems from a report, I once read, of the deaths of sewer workers in a partially drained iron pipe from oxygen depredation. My possible take
is that a rough iron surface freshly scrubbed by sewer generated acid and/or newly forming ferrous, developed a big appetite for the available oxygen.
One possible reaction could be given by:
4 Fe(ll) (aq) + 4H+ + O2 → 4 Fe(lll) + 2 H2O (see http://corrosion-doctors.org/Experiments/rust-chemistry.htm )
And a similar reaction with Cu(l), acid and oxygen. The role of salt is to serve as a good electrolyte for the electrochemical reaction, which can be
described by:
Cathode: O2 + 4 H+ + 4 e- ---> 2 H2O (see page 20-13 at http://www.public.asu.edu/~jpbirk/CHM-115_BLB/ClassNotes/chp... )
Anode: Fe (s) ---> Fe(ll) + 2 e-
Or, following the consumption of surface iron:
Anode: Fe(ll) ---> Fe(lll) + e-
[Edit] You may even get better results mixing Fe with Cu(ll), due to the expected formation of redox couples, in an equilibrium reaction:
Cu(ll) + Fe(ll) = Cu(l) + Fe(lll)
[Edited on 4-3-2017 by AJKOER]
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Acuyo
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FWIW I've heard of people who simply need an inert, and not necessarily nitrogen atm to use "canned air", apparently most brands are quite inert to
much of anything, although I did hear about one brand to avoid -- sorry that I don't remember more, but it's an idea, just reads the msds before use..
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yobbo II
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An engine exhaust has been used as an oxygen free source in places.
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Metacelsus
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Depending on the particular reaction, you might be OK with just keeping it in a tightly sealed vessel with minimal headspace. You'd lose a few percent
yield, but it wouldn't cause major problems.
However, some reactions are very air-sensitive (especially those employing oxygen-sensitive catalysts) and this wouldn't work for those ones.
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unionised
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Well, part of the answer to the OP is to buy something like this
https://www.amazon.com/Professional-Flushing-Nitrogen-cylind...
But even that's not the whole story since you need to be sure of regulating the rpessure down to a very low level (glassware will not take high
pressures safely)
Canned air is OK for a lot of things as long as it isn't heated. It depends on what you are trying to do and the OP doesn't say a lot about that.
Helium- as balloon gas- is also an option.
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Db33
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the reactions that would be done under the nitrogen atmosphere are reductive alkylation and amination followed by N-acylation. So would the yield loss
be big if these were done under normal atmosphere?
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Melgar
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Quote: Originally posted by unionised  | Well, part of the answer to the OP is to buy something like this
https://www.amazon.com/Professional-Flushing-Nitrogen-cylind...
But even that's not the whole story since you need to be sure of regulating the rpessure down to a very low level (glassware will not take high
pressures safely)
Canned air is OK for a lot of things as long as it isn't heated. It depends on what you are trying to do and the OP doesn't say a lot about that.
Helium- as balloon gas- is also an option. |
If you just want an oxygen scavenger, these are as cheap as you'll get, and actually work very well:
https://www.google.com/shopping/product/8809343064370531838
They're just filled with reduced iron particles, salt, and a bit of moisture to catalyze their oxidation fast enough to heat them. I don't think
they'd scavenge CO2 though. For that, you'd probably need an alkali hydroxide or similar.
Keeping your solvent at reflux is one common way to keep air out, since the solvent vapors displace air.
Argon is probably cheaper than helium, since it's extracted as part of normal air processing. It certainly is cheaper per unit mass. It also
wouldn't leave nearly as quickly as helium would through a small leak, since it's approximately the same density as air is. You can get larger
amounts from welding supply places, and smaller amounts from neon sign stores.
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unionised
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The only advantage to helium is that you can buy it from the supermarket
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PirateDocBrown
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One inexpensive route could start using automotive refrigerant. It's cheap and readily available, even at Wal Mart. Simple regulators are also sold
for it.
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Zyklon-A
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If you're not invested enough to consider a cylinder, there's lots of options to choose from. Running air through a reduction tube and is cheap
and can be efficient. But it's not a quick build and tedious if you skimp on materials.
If you have ammonium chloride and sodium nitrite you can generate nitrogen with no special apparatus. You'll only have water vapor to deal with
There's lots of different reactions that work too, but this is the only one I've used.
I know many (maybe all) helium balloons have oxygen added, I would imagin balloon filling cylinders will be premixed so pay attention.
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Lambda-Eyde
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Buy a one liter disposable tank of nitrogen or argon for welding, they are cheap enough and readily available if you know where to look. Get a
suitable regulator for it, a hose and a ground glass tubing adapter and you have everything you need for a basic inert atmosphere setup. As long as
this can be had so cheap there are no good reasons to be dicking around with helium, carbon dioxide, refrigerants, makeshift oxygen scavengers or
canned "air" (these are actually chlorofluorocarbons, very soluble in organic solvents but mostly inert, except for being flammable).
This just in: 95,5 % of the world population lives outside the USA
You should really listen to ABBAPlease drop by our IRC channel: #sciencemadness @ irc.efnet.org
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Db33
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its not a problem of getting the nitrogen which i should have said, my problem is how to get the nitrogen into a flask and keep it there. I saw in a
video that they used a syringe with a balloon on the end of it and that was put in the top of the flask stopper and then another needle is used to
create another hole so that the flask is flushed out an dthne i assume the syringe will slowly let more nitrogen in over time? im not sure but i need
to know how to do it without a sophisticated lab like a university.
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Tsjerk
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That is about how you do it yes. You can first flush straight from the hose, after that do the balloon thing, if you take out the "exit" needle at
some point you should be able to keep it pressurized over night. As long as your stopper or diafragma is closely fitting
What reductant do you use? If it is not LiAlH4 you should be fine without nitrogen. Often the guys and girls writing those articles use nitrogen for
about everything just because they can, using a balloon for them is easier than using a drying tube to keep water out.
Do keep water out with a tube filled with CaCl2. Even that wouldn't ruin your reaction, but better save than sorry.
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unionised
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How do you know that?
my understanding is that it's a myth.
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PirateDocBrown
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I have used balloon needles like you have described. You simply take a balloon, and seriously, in grad school they were dollar-store kids' play
balloons... and put it on a Luer-lock needle with a small rubber band. These are filled with N2 from a cylinder, similarly fitted with a hose, that
has a septum or membrane at the end.
Flasks would have a septum on the neck, and the balloon would vent through it, with a non-ballooned needle venting, also punched through the septum.
With a cannula, liquids could also be pushed by gas pressure from one flask to another.
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ahill
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I needed to exclude oxygen for some experiments I did with tannic acid - I used argon from a bottle shop (its used to keep opened wine). The gas can
comes with a thin flexible tube. If you can use a stoppable flask - great - insert the tube, then just set the stopper in the neck so that there is a
small gap for the tube - dont press it in - and squirt gas - after a few seconds, remove the tube and seat the stopper. A bit of vacuum grease might
be a good idea.
If you cant use a stopperable flask (say something like a beaker), just put it in a plastic bag, and apply gentle vacuum, or just squeeze - then
inflate it with the argon, then zip the zip or rubber band the neck, and put the whole lot on your stirrer.
Its all going to depend how sensitive your reaction is - sometimes a little O2 is fine - the reaction just cant take being constantly exposed over a
period or hours - other times - any exposure is bad. If its very sensitive - you are going to need to construct a glove box or bag.
If I search for "glove bag" on the internet, I get a lot of hits - they all look pretty expensive tho. I'd be prepared to spend a lot of time messing
with washing up gloves, plastic bags and duct tape for $1000 !
I seem to remember hearing about a procedure that would be performed in a bag to which a little dry ice had been added - the dry ice would sublime,
the bag would inflate and O2 would be displaced.
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macckone
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Carbon dioxide is a great displacer but some reactions are
ruined by it. Balloon helium is often contaminated with
significant oxygen to prevent hypoxia from kids breathing it.
Even iron reduction can leave enough oxygen to seriously
ruin a reaction. A/C refrigerant r134a is mostly
tetrafluoroethane with some pentane and butane added.
It will be inert a significant portion of reactions.
Propane is also an option that is readily available but
contains a sulfur compound, usually ethanethiol.
If you need absolute inertness, invest in an argon tank.
Small ones (20 cu ft) are about $99 at harbor freight.
*edited for formatting
[Edited on 15-3-2017 by macckone]
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Zyklon-A
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Hmm I looked around and you seem to be right. Not only is there no regulation that requires it, I couldn't find a single supplier who's MSDS don't
warn about asphyxiation.
Probably a case of unchecked wishful thinking going mainstream. Good to know.
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XeonTheMGPony
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Due to nanny statism not any more as the helium is mixed with air!
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XeonTheMGPony
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| Quote: Originally posted by Lambda-Eyde | | Buy a one liter disposable tank of nitrogen or argon for welding, they are cheap enough and readily available if you know where to look. Get a
suitable regulator for it, a hose and a ground glass tubing adapter and you have everything you need for a basic inert atmosphere setup. As long as
this can be had so cheap there are no good reasons to be dicking around with helium, carbon dioxide, refrigerants, makeshift oxygen scavengers or
canned "air" (these are actually chlorofluorocarbons, very soluble in organic solvents but mostly inert, except for being flammable).
|
Most caned air now days is diflouroEthan or 1,1,2 tetraflouro ethane (152a, 134a)
Those automotive over the counter ones will be 134a or a hydrocarbon blend.
134a is actually used as a fire suppressant in conjunction with R123. DiflouroEthan (152a) is flammable int he liquid state only but fairly inert as a
gas.
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XeonTheMGPony
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Read the lable on the tank! not all of it is don but for over the counter to joe public it is mixed with air.
HVAC nitrogen is O2 free and dried, so for purging nitrogen get it with ACR rating
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Zyklon-A
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Can you provide a reference for a company that sells such a product?
I found two relevant patents,one calls for 15-30% oxygen from 2015, the other includes oxygen and carbon dioxide, ~10% and 3% respectively. Presumably the latter is added to induce exhalation, which alone could
actually be more effective than oxygen. The last thing we need is kids who think all balloons are safe to breathe freely, since they would certainly
pass out before realizing the balloon came from a different company.
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XeonTheMGPony
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http://www.balloontime.com/products/products-list/
http://www.conwinonline.com/shop/60-40-helium-air-inflator/
| Quote: |
contain a mixture of helium and air with not less than 80 percent helium |
Even using Argon and even with the OFN (Oxygen free nitrogen) I'd still use an iron O2 scavenger, or a tube coated in Cesium will effectively (Well
very effectively) scavenge O2 it is used in vacuum tubes and halide lights as an O2 scavenger
[Edited on 21-3-2017 by XeonTheMGPony]
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Db33
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its not a question of what gas to use, im just wondering how to get it from the tank into the flask and keep it there.
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