Sciencemadness Discussion Board - Cleaning and making lithium look presentable

Cleaning and making lithium look presentable

Zan Divine - 16-5-2012 at 17:20

Having prepared large, silvery ampoules of Na & K, I needed to face my nemesis, lithium, and try to prepare a comparably sized (1" x 6") ampoule for my best customer.

I've previously uploaded a pdf file describing the significant factors that effect the deterioration of fresh Li in air. The important lesson I took from this Naval study was that Li is inert to oxygen and nitrogen as long as H2O is less than 5 - 10 ppm.

My experience has been that when lithium is melted and poured in the air, it maintains a bright surface until it cools. I can only assume that the high temperature (such as it is) maintains a localized dry zone around it for a short time.

The metal needs to be cast in some sort of mold (or does it?).
Yet no container seems suitable. Molten lithium reacts with glass, Teflon, alumina, beryllia, carbon. Casting into metal has its own problems. If the metal is hot, Li welds to it. If it's too cold, the Li freezes too quickly and won't flow.

I melt the Li in a steel piston with a SS screen in the bottom and extrude it, once molten, into...what?
I finally decided that no mold was the best mold. I extrude the molten Li out the bottom of the piston and let it form a large teardrop shaped object (sometimes as large as 3/4"). It cools in a flood of argon and that's it. I just grab the hot chunk and pop it into vacuum.

Rinse. Repeat ad nauseum. The final product is shown below.
The sample is very nice, mostly silver with some light grey and no black nitride. Always room for improvement, though.

Has anyone else dealt with these problems? How did you address them? I've been toying with the idea of using a (water jacketed?) polyethylene tube as a mold....

This is not an original observation, but the most troubling thing about this group I metal is that it thinks it's a group II metal and insists on acting like it.

[Edited on 17-5-2012 by Zan Divine]

[Edited on 18-5-2012 by ScienceSquirrel]

elementcollector1 - 17-5-2012 at 20:40

I don't know, lithium looking like that is hard to come by. I just have my ugly gray chunks with metallic edges (cut with scissors, and placed into mineral oil). Can I melt this on a stovetop under oil to get it to look better, or do I need to chemically clean it first? I heard from NurdRage that toluene (yay toluene!) works for potassium, so you might give that a go.

froot - 17-5-2012 at 23:26

Would Li react with RTV silicone rubber? If not you can make a mould with that, decontaminate and cast molten Li into that. It's flexibility would make it easy to de-mould too.

Cleaning lithium

vampirexevipex - 18-5-2012 at 04:32

Hello! I have some lithium and no matter what i do, it gets coated with a tin layer of its oxides/peroxides. I've been looking for info. in the internet and found that toluene works great with cleaning potassium, so i've been thinking of using it with lithium too, but i dont know if it could react with it. So, should i use it with lithium, and it wont react?

Arthur Dent - 18-5-2012 at 05:52

Quick question, there's already a thread just below this one entitled "Making lithium look presentable" on the subject of cleaning lithium metal. Why start a new thread on the same exact subject?

Robert

Zan Divine - 18-5-2012 at 09:44

Quote: Originally posted by elementcollector1

I don't know, lithium looking like that is hard to come by. I just have my ugly gray chunks with metallic edges (cut with scissors, and placed into mineral oil). Can I melt this on a stovetop under oil to get it to look better, or do I need to chemically clean it first? I heard from NurdRage that toluene (yay toluene!) works for potassium, so you might give that a go.

Toluene and sodium can be upgraded by melting under toluene (see details in my topic "Shiny ampoules of Na and K") and stirring. This also removes that damned mineral oil.

With Li this isn't possible since Li melts 70+ degrees C higher than toluene boils (behaving more like a group II metal). Li can be melted in mineral oil but it floats on top and isn't very protected by the liquid.

Zan Divine - 18-5-2012 at 09:50

Quote: Originally posted by Arthur Dent

Quick question, there's already a thread just below this one entitled "Making lithium look presentable" on the subject of cleaning lithium metal. Why start a new thread on the same exact subject?

Robert

That is, or was, my thread. I have no idea how the "Cleaning and" got tacked on to my title. I don't even see my original thread listed anymore.

[Edited on 18-5-2012 by Zan Divine]

Zan Divine - 18-5-2012 at 09:55

Quote: Originally posted by froot

Would Li react with RTV silicone rubber? If not you can make a mould with that, decontaminate and cast molten Li into that. It's flexibility would make it easy to de-mould too.

RTV silicone is perfect on several counts, but on the reactivity issue, it falls flat. Molten Li will chew it up. Thanks for the suggestion, though. The reason I was leaning toward a polyethylene is that it just has C-C and C-H bonds and these are resistant.

[Edited on 18-5-2012 by Zan Divine]

ScienceSquirrel - 18-5-2012 at 09:55

I have merged the two threads.
Your thread is most of it and I tacked cleaning on the title to cover vampirexevipex's query.
Nothing is gone.

Zan Divine - 18-5-2012 at 10:05

Quote: Originally posted by vampirexevipex

Hello! I have some lithium and no matter what i do, it gets coated with a tin layer of its oxides/peroxides. I've been looking for info. in the internet and found that toluene works great with cleaning potassium, so i've been thinking of using it with lithium too, but i dont know if it could react with it. So, should i use it with lithium, and it wont react?

Sorry, I overlooked this question when answering a similar one.
The problem is moisture. It catalyzes the reactions with O2 & N2. The dark color on Li is Li3N, lithium nitride. One lone N2 molecule takes out 6 Li atoms in the process. I'm afraid that what works nicely for Na, K, etc. often fails miserably for Li.
Toluene won't react with Li but it won't melt it either.

The only method I have cleaned Li with (successfully) is mechanical.....melting it in a confined area and pushing the melt through a filter of SS mesh. The one improvement I envision is using SS wool to filter out the smaller detritus better than a fine mesh can.

In fact, I'm going to go take a picture of the crude piston to make its construction clearer in case others try this....brb....

There! Not pretty, but it's a disposable thing.

[Edited on 18-5-2012 by Zan Divine]

elementcollector1 - 19-5-2012 at 19:45

Is there a solvent that is lighter than lithium?

Zan Divine - 20-5-2012 at 04:44

There is no solvent that is inert to molten lithium and that boils high enough to melt it. Even the lightest solvents, like pentane, still weigh 20% more than lithium (and boil way, way too low).

I'm fairly confident in saying there is no known solvent in which you can melt Li and have it sink to the bottom.

The d of Li is just slightly over 1/2 g per mL, most solvents fall into the range of ~0.6 to ~1.5 g per mL.

[Edited on 20-5-2012 by Zan Divine]

Arthur Dent - 20-5-2012 at 06:01

Quote: Originally posted by Zan Divine

In fact, I'm going to go take a picture of the crude piston to make its construction clearer in case others try this....brb....

There! Not pretty, but it's a disposable thing.

Cool apparatus! Is the piston a tight fit? I ask because I was wondering if upon heating, the metal expands and would seize the piston?

And when the apparatus is heated, in what vessel do you "squeeze out" the molten lithium?

As for solvents or mineral oils, it is indeed a damning thing that Lithium floats even the lightest inert solvent or oil. I tried to keep some in a jar but after some time, it just oxidizes to hell because it just won't stay down.

Robert

phlogiston - 20-5-2012 at 06:06

Is it soldered all way around or is it held together with tack weld(s)?

Adas - 20-5-2012 at 07:12

DMSO - density ~1g/cm<sup>3</sup>, BP 189°C, while Li's MP is 180°C

barley81 - 20-5-2012 at 09:42

DMSO would probably react with lithium. It has an oxygen atom, and as Nicodem mentioned in a thread recently, it can act as an oxidizing agent.

elementcollector1 - 20-5-2012 at 10:49

What if you put a steel container over the lithium, under the oil? The container would catch the lithium without oxidising it, maybe.

Zan Divine - 20-5-2012 at 14:00

Q) Cool apparatus! Is the piston a tight fit?
A) The piston is not particularly tight.

Q) And when the apparatus is heated, in what vessel do you "squeeze out" the molten lithium?
A) "I finally decided that no mold was the best mold. I extrude the molten Li out the bottom of the piston and let it form a large teardrop shaped object (sometimes as large as 3/4"). It cools in a flood of argon and that's it. I just grab the hot chunk and pop it into vacuum." The Li just hangs there cooling. It looks like a punching bag.

Q) Is it soldered all way around or is it held together with tack weld(s)?
A) 2 tack welds. No solder. The cylinder had a nice, flat, smooth face. No leaks of molten Li since the Li is never under much pressure

Q) DMSO - density ~1g/cm3, BP 189°C, while Li's MP is 180°C.
A) There are lots of solvents with bp >180 C. None are less dense than lithium. Also, as noted, DMSO reacts with Li.

Q) What if you put a steel container over the lithium, under the oil? The container would catch the lithium without oxidising it, maybe.
A) You can let the Li splash into the mineral oil and it gets coated on all sides. The best alternative, if you want to use oil, is to fill the jar completely after adding the Li so that there are no air bubbles.

Also, if you do use oil, heating under vacuum and/or predrying by melting Na or K in it and stirring are good ideas. Do you have a feeling for exactly how low 5 ppm H2O is? Those are glovebox conditions. It's hard to dry things like oil that well.

Bubbling argon through the oil to sparge out the O2 and N2 helps too.

[Edited on 21-5-2012 by Zan Divine]

Zan Divine - 21-5-2012 at 19:12

Quote: Originally posted by Zan Divine

There is no solvent that is inert to molten lithium and that boils high enough to melt it.

Jesus! Did I say that?!
Well, OK...but what I meant to say was "There is no solvent lighter than lithium that boils high enough to melt it."

[Edited on 22-5-2012 by Zan Divine]

elementcollector1 - 21-5-2012 at 19:50

Really, something to trap the lithium under the mineral oil would be ideal. An inverted crucible, submerged in the oil? Just heat to melt, and when it's done, flip it over (still under the oil), take out the lithium (while holding it under oil), and transfer into container and environment of your choice.
Oil.

Zan Divine - 22-5-2012 at 20:11

The purification happens during the filtration. You can't omit that.

elementcollector1 - 22-5-2012 at 20:33

What do you use for the filter again?

Zan Divine - 23-5-2012 at 04:40

I use stainless steel mesh. I plan to try stainless steel wool (the same filtering medium I used with Na & K) next because it will filter out finer particles.

[Edited on 23-5-2012 by Zan Divine]

vmelkon - 25-5-2012 at 08:19

Quote: Originally posted by Zan Divine

With Li this isn't possible since Li melts 70+ degrees C higher than toluene boils (behaving more like a group II metal). Li can be melted in mineral oil but it floats on top and isn't very protected by the liquid.

If you have a container that can hold enough pressure, toluene's boiling point would rise above the mp of lithium. I don't know how much pressure you need to handle and I imagine an explosion will spread lithium all over the place.

You could also try xylene (bp = about 138 °C), available at the hardware store, + some pressure.

[Edited on 25-5-2012 by vmelkon]

Lambda-Eyde - 25-5-2012 at 08:28

Paraffin oil has a high boiling point. I'm not sure if it would react with lithium, though. Tetralin boils at over 200 degrees, but it's harder to procure. I doubt it would react with alkali metals in the same fashion as naphthalene, IIRC Nurdrage used tetralin in one of his potassium experiments.

elementcollector1 - 25-5-2012 at 14:18

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.

Zan Divine - 25-5-2012 at 16:04

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]

Lambda-Eyde - 25-5-2012 at 16:47

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.

How about cooling it under a stream of dry argon? That would also accelerate the cooling somewhat.

Zan Divine - 25-5-2012 at 17:29

Quote: Originally posted by Zan Divine

It cools in a flood of argon and that's it. I just grab the hot chunk and pop it into vacuum.

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]

Fleaker - 27-5-2012 at 17:16

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.

Zan Divine - 27-5-2012 at 19:16

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]

Arthur Dent - 28-5-2012 at 03:35

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

Zan Divine - 28-5-2012 at 06:03

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!

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]

papasmurphie - 30-5-2012 at 13:01

About how much does that cost?

Zan Divine - 30-5-2012 at 14:36

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]

S.C. Wack - 30-5-2012 at 15:26

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]

Zan Divine - 1-6-2012 at 15:50

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]

elementcollector1 - 6-12-2012 at 20:12

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.

chemrox - 7-12-2012 at 17:48

I have some cold lithium tape in MeOH and I don't have any MeLi yet.

SM2 - 7-12-2012 at 17:55

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

Bezaleel - 10-1-2013 at 09:16

Quote: Originally posted by Zan Divine

I can be sure that a 0.001 mm Hg vacuum is drier than any argon atmosphere I can supply.

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.

elementcollector1 - 10-1-2013 at 09:47

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?

elementcollector1 - 14-1-2013 at 21:17

An improved version of my earlier idea of a submerged SS crucible. Thoughts?

Attachment: lithiumproduction1.pub (110kB)
This file has been downloaded 560 times

S.C. Wack - 11-10-2014 at 08:35

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)
This file has been downloaded 487 times

Dan Vizine - 18-10-2014 at 09:58

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.

S.C. Wack - 18-10-2014 at 11:05

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?

Dan Vizine - 18-10-2014 at 16:39

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.

diddi - 18-10-2014 at 21:15

try casting Li into graphite mould.

Dan Vizine - 19-10-2014 at 10:12

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.