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elementcollector1
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apparently, tetralin can be synthesized from reducing napthalene dissolved in decane (or another neutral hydrocarbon) with sodium (sodium WHAT?) and
adding ethanol.
Source: http://www.instructables.com/id/Make-Potassium-Metal/
NormReitzel says:
Nice video. In the US patent for this method, the sodium synth uses preformed sodium alcoholate. I'd like to suggest trying n-butanol or n-pentanol as
the catalyst.
There is also a published synth using sodium in ethanol to reduce naphthalene to tetralin and then on to decalin. I've actually run this reaction, and
yields are a lot higher using a neutral (decane) hydrocarbon with naphthalene dissolved in it, adding sodium, and reducing with ethanol.
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Zan Divine
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I think some of you may be missing the point. We already have a liquid in which you can melt lithium, mineral oil.
What the others desired is a nice solvent to melt Li under in the air. One where the Li doesn't rise to the top. It doesn't exist but it doesn't
matter since it's not needed.
I've even melted Li in a steel spoon with a propane torch. You can then pour clean Li from under a crust of hydroxide & nitride. Melting is the
easy part. It's the cooling that is 99% of the challenge. The slightest pickup of any H2O is the beginning of the end. The darkening starts and
spreads throughout the sample. It is very important to understand the powerful catalytic effect that moisture exerts.
[Edited on 26-5-2012 by Zan Divine]
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Lambda-Eyde
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Quote: Originally posted by Zan Divine  | I think some of you may be missing the point. We already have a liquid in which you can melt lithium, mineral oil.
What the others desired is a nice solvent to melt Li under in the air. One where the Li doesn't rise to the top. It doesn't exist but it doesn't
matter since it's not needed. |
D'oh! I completely forgot that when writing my post, sorry.
| Quote: Originally posted by Zan Divine | | Melting is the easy part. It's the cooling that is 99% of the challenge. The slightest pickup of any H2O is the beginning of the end. The darkening
starts and spreads throughout the sample. It is very important to understand the powerful catalytic effect that moisture exerts.
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How about cooling it under a stream of dry argon? That would also accelerate the cooling somewhat.
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Zan Divine
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If you look back, I first debated the choice of mold and decided that no mold is best. The reason is that if the molten lithium touches the wrong
surface (one with adsorbed moisture) it WILL darken.
I cool it in argon already.
Here are some interesting, maybe even useful, facts about lithium from a paper I have concerning the construction of a lithium evaporator.
• Molten Lithium has a tendency to do what it wants to do which may or may not be what you want it to do.
(OK, not so much a "fact", but very true)
• Generally, molten lithium (up to ~ 300° C) does not flow with adherence to 304 stainless steel. However, adherence to stainless steel is
observed when it is at or above the melting point of lithium (180.5° C) and immersed into molten lithium.
(Or vice-versa, the "sticking" problem I mentioned with some 302/304 SS molds I tried )
• For molten lithium ≥ 500° C on 304 stainless steel, gravity is irrelevant. Molten lithium hydroxide (m.p. 471° C) will flux the surface
in all directions and the molten lithium will follow.
(Fascinating. Probably kind of alarming at times)
• While other materials of construction (e. g. molybdenum, tungsten, and tantalum) may seem to be a better choice, they pose other more difficult
problems than 304 stainless steel.
(Of course, it's NEVER simple with lithium....)
[Edited on 26-5-2012 by Zan Divine]
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Fleaker
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Can it be melted in a graphite mold in vacuo via resistive heating, then cooled, back flushed with argon and then placed in the ampoule?
We have a bear of a time melting palladium--any oxygen that is stuck to it will make it very brittle and unsuitable. The only solution has been to
vacuum melt it.
Neither flask nor beaker.
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Zan Divine
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Hi Fleaker,
If the graphite mold has been thoroughly outgassed previously, probably. At some temperature, Li and C react to give the carbide, Li2C2, but you'd
stay below that. I think this is what would happen..the Li would melt OK if temperature is controlled, but it would stick to the graphite to some
extent and when demolding you'd likely have black spots. The manipulations needed to remove these would require tools that are clean and free of
adsorbed water and very effective argon blanketing by very dry argon (<5 ppm H2O). If your argon is wetter than this, catalytic trouble could soon
be headed your way.
That's the reason I prefer to keep Li in a vacuum versus argon. I can be sure that a 0.001 mm Hg vacuum is drier than any argon atmosphere I can
supply.
Really, SS 304 is great for melting and is a pretty good mold material if it is thoroughly dried and atmospheric control is good enough. If you have
enough really dry argon you are pretty likely to have good results.
[Edited on 28-5-2012 by Zan Divine]
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Arthur Dent
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Zan, I would really like to see a picture of the apparatus you use to package your ampoules under vacuum. I was trying to imagine the mechanism and
just can't picture it. I fear it would be a device well beyond the means of the average home chemist.
Your alkali metal ampoules are absolutely beautiful and probably the holy grail of any element collector.
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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Zan Divine
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| Quote: Originally posted by Arthur Dent | Zan, I would really like to see a picture of the apparatus you use to package your ampoules under vacuum. I was trying to imagine the mechanism and
just can't picture it. I fear it would be a device well beyond the means of the average home chemist.
My method is actually relatively crude and simple. It takes a bit of manual dexterity though. The reason for that is the
item being packaged.
Consider: If you ampoule a liquid (or anything easily liquified like Na or K), you get to use an ampoule with an already narrowed section which is
very easy to melt shut without "blow-ins" or thin sections. When the ampoule contains big lumps, the lumps are added, vacuum applied & you then
you have to very carefully try to neck a large tube (for me, 3/4" or 1" Pyrex) down to a seal in a controlled fashion. The actual appratus is just a
tube sealed at one end. The other end is sealed by a rubber stopper with a hose barb which is connected to a vacuum pump. The tube is charged, the
stopper inserted and vacuum applied. The tube is carefully narrowed in the flame and sealed. This operation is not likely to work for someone who
doesn't have at least basic glassblowing skills.
The device I use for Na & K (described in my thread about preparing those samples) looks harder to make but the opposite is true. You get to make
it without its payload, you load it up, and since Na & K are more forgiving of oxygen & inert to nitrogen, you get to narrow the neck under a
weak vacuum provided by a squeeze ball connected to the ampoule. Then you can let it cool, apply full pump vacuum and seal it up. Also, the
purification happens next, inside the good vacuum, so any previous results of exposure are stripped away. With Li, you've got what you've got.
Your alkali metal ampoules are absolutely beautiful and probably the holy grail of any element collector.
Thanks, Robert!
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I realize that vacuum pumps, glassblowing supplies and the like may not be standard in many homes. In these cases, I think the mineral oil techniques
briefly explored by elementcollector1 several posts back have the best chance of giving good results. I can't stress too heavily that the oil needs to
be pre-purified. Dissolved oxygen & nitrogen, as well as moisture, MUST be removed. Otherwise, the sample will slowly darken over time in a
diffusion-controlled process.
[Edited on 28-5-2012 by Zan Divine]
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papasmurphie
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About how much does that cost?
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Zan Divine
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Papasmurphie, could you be a little more specific? Do you mean the equipment, the finished product or what?
I just bought another quarter pound of lithium since so many people want samples. Looks like the Li R&D will continue. I thought this detour on
the way to Rb was over.
I'm actually going to put a little effort into trying to cast into jacketed HDPE or similar. It sounds crazy but if it works it may give really
brilliant Li. The first simple-minded scouting run will just be to use something easy to machine like Al or type metal to make a metal jacket for a
commercial disposable plastic syringe. Melt Li using a heating element/thermocouple (instead of my usual torch) so that it's not too hot (or any
hotter than it has to be) and try it. I just fear that some trace impurities in the plastic will cause problems.
[Edited on 30-5-2012 by Zan Divine]
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S.C. Wack
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You have of course seen J Chem Ed 515 (1954), which more or less ends with molten Li sucked up with an oil-coated steel pipet?
[Edited on 31-5-2012 by S.C. Wack]
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Zan Divine
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No, I haven't. Thanks for the link. It's interesting, but it ends with:
"The metal could then be coated with oil or simply allowed to nitride in air to form a protective coating of its own. The former method was found to
be the more satisfactory."
The thing is, I don't want to use oil.
"In some cases the glass tubes were sealed off and in others the pieces of metal were removed into containers filled with oil
(Figure4). Both types of containers kept the lithium shiny for many months."
My product already stays shiny indefinitely since it's in a vacuum. I just need ways to make it perfectly shiny everywhere with no areas of dull
silver. My goal is brilliant silver-white. I'd also like to find a means of casting regular shapes instead of relying on gravity & surface tension
and the shapes they produce. A cylinder would be nice.
[Edited on 1-6-2012 by Zan Divine]
He who makes a beast of himself gets rid of some of the pain of being a man. --HST
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elementcollector1
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Can you seriously melt lithium in a spoon with propane? I have to go try that. An improvement to the process would be to pour this molten lithium into
a steel strainer over cold mineral oil, then ampoule it.
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chemrox
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I have some cold lithium tape in MeOH and I don't have any MeLi yet.
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SM2
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What you do is cut the lithium under your solvent, but you add a little cyclomethicone, and an even smaller amount of dimethicone to the mix. If done
properly, you will be able to wipe these dry, and the lithium will stay shiny for hours
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Bezaleel
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I wonder, what kind of vacuum pump do you use to generate a vacuum of this pressure?
Pressures of around 1 Pa are not within every home scientist's scope, I guess. I own a rotary vane pump, which is (when used carefully) capable of
creating a vacuum of this pressure, but traces of pump oil will be unavoidable, for which reason oil based pumps have been abandoned in virtually all
physics experiments today.
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elementcollector1
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| Quote: Originally posted by SM2 | | What you do is cut the lithium under your solvent, but you add a little cyclomethicone, and an even smaller amount of dimethicone to the mix. If done
properly, you will be able to wipe these dry, and the lithium will stay shiny for hours |
Are there any substitutes to these, and if so/not, where do I find them?
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elementcollector1
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An improved version of my earlier idea of a submerged SS crucible. Thoughts?
Attachment: lithiumproduction1.pub (110kB)
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S.C. Wack
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One of the simpler drawings from Anorganisch-präparative Chemie has an elegant method for vacuum ampouling lithium. Of course this 1950 time capsule has a bit more general
laboratory odds and ends detail than any similar English-language book, and the Li apparatus (among others) isn't in any of your drawers.
Attachment: grubitsch.pdf (1.1MB)
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Dan Vizine
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S. C. Wack,
Google translate gives this horrible translation. It's so bad that I can't even understand it...
To remove residual melt from the Reguli, melts to the lithium at about 200 0 in paraffin (paraffin first with Na-wire dry) to, and washed with
anhydrous Benzin1.
Lithium is a silvery-white, lustrous metal with a tinge of yellowish. Heated in air, it burns with a white flame. At the temperature its melting
point, it reacts with glass or Quartz under browning (Siliziumahscheidung). about it still melt down blank, washing the Pieces volatile in anhydrous
benzene, to the to remove adhering liquid paraffin, located on a Filtrierpapierunterlage with a knife Oxydkruste and raises the metal immediately in
the, for 2 hours at 300 in high vacuum Water skins liberated, filled with dry air Glass tube Fig. 290, it pulls up to a narrow Lumens, evacuated,
melts at A and warms Abb.200. the metal to by fanning the flame until it Einschmel- melts and silver white, leaving a zen of Lithium. Oxide film in
the slightly preheated Abschmelzgefäß fließt2 • After solidification of the metal removed the "funnel" by turning the whole Apparatus and melts
the tapering off at B.
Would you care to translate the pertinent parts? I'm interested in understanding whatever it is that they are saying.
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S.C. Wack
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My translation skills are generally sucky and undesirable...especially since I don't see why the ampoule of almost clean Li needs to start out so far
from the restriction/new ampoule neck when evacuating, or why point A would be exactly as illustrated...and you are in a better position than anyone
to answer whether spot heating of Li in contact with glass and some manual fussing can melt Li while leaving oxide or whatever on the original ampoule
along with hopefully not much reaction with the glass.
Not one but three small restrictions as illustrated might require a bit of pumping time for a full evacuation?
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Dan Vizine
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Thanks for the reply S.C.
Part of the reason for my curiosity is because of my own experiences with Li. I thought that they were suggesting that lithium can be melted in glass
and you've confirmed it.
No matter how brief the contact, in my hands, the glass was attacked almost instantly. It started with a rapid blackening and the liquid Li ate
entirely through ~1 mm of borosilicate in 5 or 10 seconds.
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diddi
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try casting Li into graphite mould.
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Dan Vizine
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I've tried graphite, but the metal in contact with the mold darkened. I think that it may work better if it is pre-baked, which I didn't try.
A glassy carbon vessel may be ideal, easy to bake off the surface moisture, smooth and quite inert to many things.
I'll probably try the baked graphite sometime in the future.
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