h a l f b a k e r y"My only concern is that it wouldn't work, which I see as a problem."
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It appears that lithium will react with nitrogen at room
temperature to form solid lithium nitride. It looks like it
will also oxidize. So if some quantity of finely powdered
mostly pure lithium is placed in a sealed container, possibly
up to 99% of the air will react and turn to a solid, creating
a low vacuum. I was starting to try to figure out if other
gasses could be captured, like CO2, etc, but realized that's
pointless since almost 1% of air is argon, which won't react
with anything.
So what would this be good for? Well vacuum pumps are
expensive, and if you just need to create a vacuum on rare
occasions, this might be just the thing. Ideally this could
be sold in a tea-bag-like pouch sealed inside a foil wrapper.
Tear the foil open, toss it in the container and close the
lid. You might want to shake it around a bit (after eh lid is
closed) to help the air distribute throughout the powder
more quickly. I envision using this for the feather drop
experiment in classrooms with a long clear tube. When
you first throw the pouch and feather into the tube,
turning the container over will result in the pouch falling
faster than the feather. As the vacuum is improves, the
feather will fall faster and faster.
To get a higher vacuum, the container could be purged
with nitrogen to reduce the concentration of argon and any
other gasses that won't react with lithium.
Still unresolved (since I'm too lazy to research this at the
moment): Just how dangerous is pure lithium? I don't
suppose the US Postal Service would want to deliver this.
If it's packed to look like a tea-bag, how do we ensure that
no one drops it in a cup of hot water? How do you safely
dispose of the lithium Nitride when you're done? How
much finely powdered lithium would be needed per quart
of air at sea level, and how expensive would that be?
Lithium properties
https://www.webelem...hermochemistry.html
Well, the thermochemical properties; links there to physical etc... [neutrinos_shadow, Nov 17 2020]
Why?
Why_3f
by xenxag [pashute, Nov 19 2020]
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If you can make lithium hypochlorite, there's a world-wide
shortage of it now for pools and spas. All the lithium
makers ditched it to make batteries but too many came
online and the price of lithium dropped. I bought a couple
years' worth of lithium hypochlorite but I'm almost out. |
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For a cheaper method, purge the tube with oxygen and use moist iron (e.g. steel wool). |
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Lithium is reasonably dangerous. In the presense of moisture, it causes chemical burns and can spontaniously combust. You can make your own metallic lithium by electrolysing a molten lithium salt, but it is kind of dicey and should be done in a vacuum :-/. |
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The problem is leakage. No vacuum system is ever perfect, and hydrogen can diffuse through metal at a disconcertingly high rate. So your absorber (and sorbtion pumps are Baked and WKTE) will eventually saturate and the volume will start to move back towards equilibrium with its environment. |
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There are cryopumps, sputter-ion pumps that capture gas molecules, and thermionic valves (tubes) often have a titanium "getter" which presents a reactive surface to grab gas ... but just about all vacuum systems have to be constantly pumped to maintain the pressure. |
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Reactive pumps for creating vacuum are not an innovation. |
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Also, Lithium is very boring and lacks entertainment value compared to the other alkali metals. |
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That's just the normalizing feeling you get after you take your
dosage of it to help with the desires to take over the galaxy
and "mood swings," 8th. |
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[8th] Thanks for the search term "reactive pumps" and
"getter pumps" which get a lot more hits than chemical
vacuum pump. |
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I guess what I reinvented is a getter, though it sounds like
most of those are heat activated (probably for good
reason). Since this is WKTE do I need to MFD? |
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I wasn't concerned about maintaining a vacuum long
term. Just long enough to complete some task or run
some experiment. Of course diffusion through the foil
wrapper would be a problem with storage of the lithium
before use. I guess that explains the heat activated
getters... |
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[spidermother] I like the idea of your cheaper method.
But then thought: wouldn't all the moisture turn to water
vapor, reducing the vacuum? Then I checked the vapor
pressure of water at 25C. That's 0.03 atmospheres: not
quite as good as I was theoretically aiming for, but
reasonably close. |
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With that in mind, rather than trying to get oxygen to
flush the chamber, just flush it with steam, cap it and let
it cool. Throw it in the freezer (-18C) to get it down to
0.0012 atmospheres assuming the temperature and
fogged glass don't mess with the experiment you're trying
to perform. ... Which I see after a quick google is a
widely used method of demonstrating vacuum ... |
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If you add the right amount of water to the iron, it ends up as water of hydration; the water is chemically bound to the iron oxide, so it doesn't end up as water vapour. In theory. |
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I wouldn't delete it. Your idea is to chemical vacuums as those coffee machine single packs are to coffee. |
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As in "More expensive on a per-unit basis, ties you to a specific supplier, more environmentally damaging, and the result is no better than existing methods" ? |
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There's no need to thank us; we welcome the opportunity to expose your pitiful ignorance to the world. Don't hesitate to ask us if you feel in need of a further bout of gratuitous denigration and public humiliation. |
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// Since this is WKTE do I need to MFD? // |
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We ddn't MFD it as it's the equivalent of a corpse hanging in a gibbet-cage; a horrible warning to onlookers, and something tasty for the crows to peck at... |
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//lithium hypochlorite, there's a world-wide shortage of
it now for pools and spas.// |
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I wonder why the cation matters? I can't see why
sodium, potassium, calcium or magnesium wouldn't work
just fine? Potassium might be expensive and Calcium
might give some precipitation issues in hard water, but
that could be dealt with using EDTA. |
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It's a shame H2O2 isn't cheaper, that's a great disinfectant
and has the good manners to disappear discretely after a
short while. |
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//There's no need to thank us; we welcome the
opportunity to expose your pitiful ignorance to the
world.// |
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The problem is the sheer productivity of the ignorant vs
hours in a day. |
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"While there is clearly an upper limit to human intelligence, there is no such limit to human stupidity". |
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>and should be done in a vacuum. - MFTagline |
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> Also, Lithium is very boring...
That's what Boredom specialist and [["Why?"]] are for. (see
link) |
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