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Author: Subject: Cesium from CsCl
Zan Divine
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[*] posted on 3-12-2011 at 21:21


Just made Cesium


Well, it was too damn easy.
Used patent US3164461.
This is a Li metallothermic redn. in vacuo @ 585 degrees C.
Yield is nearly quantitative in about a total 15 min of reaction time (at temp).
CsCl electrolysis - such a bad idea no comment necessary
CsOH + Mg - Just wait until you price CsOH.....Work up sucks
CsCl + CaC2 - lower yield, higher temp
Cs azide - Hah! Just try to get barium azide
I spent hours thinking about this before jumping in. CsCl + Li (or Ca) is the only way worth considering. Esp. if, like me, you copped 250 g of CsCl for $50 on e-bay.
Rubidium next...maybe. RbCl is $350/50g from only source I've found. Yeah, That'll be the friggin' day.....
Ahhhh....how about this?....Got a Rubidium halide? Want Rb metal? I'll do it for 50%.

PS What is that "harmless" doing under my name? You apparently don't know me......
PPS Yeah, I KNOW the pics suck. If you want to see full size ones I think this will do it:

http://i43.tinypic.com/drcl5l.jpg[/IMG]

http://i43.tinypic.com/20fpzsw.jpg[/IMG]

One of the harder things about making Cs was wading through the information/disinformation. Most notably: Cesium is pyrophoric. No, it isn't. At least not at 70 degrees F and 66% relative humidity. When I opened the reactor, I expected fire. The only fire I saw was when I touched molten Cs with a leather welding glove. Amusing.



The Process sm.jpg - 108kB The Setup sm.jpg - 88kB







[Edited on 4-12-2011 by Zan Divine]
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[*] posted on 4-12-2011 at 07:05


Interesting! Reduction of CsCl with Li and removal of Cs by vacuum distillation, if I understand well? Could you provide some more details, please? And more photos of the metal too, does it have that slightly golden shimmer that is claimed?

Is that a hair drier on the left photo?

('harmless' is an attribute any new member here gets. Not to be taken seriously)



[Edited on 4-12-2011 by blogfast25]




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Zan Divine
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[*] posted on 4-12-2011 at 08:09




This is a screenshot of the US patent. With % yields like those, and especially with the high purities reported, it's hard not to sigh and wish they hadn't made it so easy. I'd love to claim that my Cs was the end result of painstaking trials eventually culminating in sucess, but the truth is that I just followed the instructions.

This 12.5 g rxn. (of the cesium salt) was a quick and dirty scouting run whose main purpose was to get experience in handling Cs and to investigate if the physical construction of my apparatus was suitable.

Among my main questions was this one: Given that Cs vapor leaves the reactor near 600 degrees C, would I need to cool the exit pipe with water? ...or...maybe I'd need to heat it if the Cs froze in it? It was the latter, and that's the reason for the home-built high temp heat gun. Cs tended to freeze in the narrow downwards tube in the center of the vacuum take-off adapter as well as in the last few inches of the 12" long 1/4" stainless steel pipe. Gentle warming solved this problem.

My reactor is a stainless steel tube unto which I welded a standard ferrous pipe fitting (I really don't see why SS is mandated. Steel is suitable, as is monel.) allowing me to attach/detach the condenser pipe for charging/cleaning.

This is actually something I made for my phosphorus project. I'm going to make samples of all of the hard to get, "big-game" elements and offer them on e-bay to other collectors who shouldn't have to pay $100 - $140 per gram for Cs or Rb and those who should be able to buy a small sample of white P without selling their first-born. Bromine was first, cesium is in progress, rubidium will be next and then possibly white P. I need to see how dickish the DEA is about gram quantities. We all know that I2 and P are watched because of their methadrine connection, yet I see dozens of iodine samples for sale and a few (only red) P samples and as long as they are small, seem to elicit no hysterical overreactions.

I'll post pics today or tomorrow of my production scale apparatus which uses part of a SS "lecture bottle" (for gasses) as the reactor and an old heating element from an oven to provide a nice, sheathed source of heat.

The crude metal was submerged in mineral oil and it's hard to see it because the high index of refraction of the oil distorts the image in the small flask. In the future the receiver will be sized so that it is full at the end of the reaction. Now that the prelim. results are in and it's thumbs up, I'm going to rent an inert gas cylinder (big deposit, heavy pain in the ass) or see if heating (NH4)2Cr2O7 gives me a usuable grade and amount of N2. I'm going to eventually use a glove-bag & inert atmosphere to package samples.






[Edited on 4-12-2011 by Zan Divine]
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[*] posted on 4-12-2011 at 08:35


Thanks, Zan!

Considering how peacock proud several of us were for making gram amounts of potassium metal with a procedure that’s quite unique and interesting but takes about 3 hours to complete, this is a remarkably quick and easy way of doing things and obtaining the ‘emperor of metals’!

For heating the ‘condenser tube’ you might consider the sort of heater coil amateur astronomers use to prevent their telescopes from frosting over on a cold night. Or a ‘heater ribbon’ home brewers use to keep their fermentation buckets in the right temperature range. Both are very low power heaters that should allow to keep the condenser just above 30 C. Very 'off the shelf'.

As regards selling the stuff, good luck with that: the market can’t be very large but competitively priced you might sell quite a bit of it…

I'm betting this thread will go 'sticky' in no time...

The patent in question.



[Edited on 4-12-2011 by blogfast25]




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Zan Divine
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[*] posted on 4-12-2011 at 10:35


I'm aware of the method. It was actually the method I was going to use before I remembered that I had a monel 24/40 joint which allowed a vacuum-tight metal-to-glass transition. [ In reterospect, this is actually overkill as, by the time cesium reaches this area, it's only barely warm and, as long as the central SS tube extends past the seal area, won't touch the seal anyway.]

I also was deterred by the high cost of CsOH. I had a quote of $520/100g + shipping of ~$100 (wtf is THAT about?).

To anybody considering the quest for the heavier group 1 elements I can't emphasize how limited you are without a good vacuum pump. When I recently bought my used pump on e-bay there were 2 other similar pumps I was considering, one even with a money-back guarantee, that I was sure would have worked. The prices were from $ 80 to $100 delivered. These are lab quality single-stage oil-filled pumps capable of 0.01 mm Hg or better. Buying tips: look for units that look like they were plumbed in vs. having hose connections. Those encounter less abuse. If a unit is sold untested look at the pic. Is the cord missing? It was probably hard-wired in & working when salvaged and the seller just didn't want to take the time to attach a power cord to test it. Vacuum pumps that have lots of splashes and stains are probably ugly inside as well. Avoid them on average. I think anyone can have a nice vacuum pump for $100 or less and you'll be pleased at the number of avenues that open up when you do.

Anyway, back to the chemistry at hand...as long as the produced metal can be volatilized much easier than can Li (BPs...671 for Cs, 688 for Rb, 759 for K, 883 for Na all versus 1342 for Li) the reaction will suceed to a greater or lesser extent. With Le Chatelier's principle in charge of the kitchen, electronegativities are irrelevant.

It may surprise some to know that carbon has been used to reduce Cs compounds to the metal. As long as CO escapes the equilibrium is pushed to give Cs metal.

And finally, I'd like to say kudos to those who succeeded in making K. I'm not yet familiar with this site and its members and achievements but I have caught on to the fact that many are self-taught or have some training and do this out of pure love of chemistry and this is inspiring.

As for me, I spent ~26 straight years doing synthesis all day long on continually changing projects plus 4 years of vacuum-line / glovebox research in undergrad. and grad. school. Backed by a very well equipped shop, an 8x10' room filled with SS, aluminium, teflon, graphite,etc ....ad infinitum, and no current outlet for my chemistry proclivities (current job is more like engineering) I troll the internet for fun things to make. I've never yet set my sights on any target except purified tantalum that I didn't achieve. Some things just require too much financial outlay.

And lastly, my primary hope with many of these samples is to trade for elements I don't have yet. These include Re and Th especially, also Os, Ir, Hf and U and the lanthanides prominently and then As, Tl, Sr, Se and a handful of others.

It's a funny thing about markets. "Sexy" elements like group 1, Br, Ga and a few others move well. I'll be offering K next week. I had beautiful Ta samples priced at 1/2 of the competition and they took weeks! Go figure.

I don't yet know about this "sticky" of which you speak.....






[Edited on 4-12-2011 by Zan Divine]
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[*] posted on 4-12-2011 at 10:55


CsOH is hellishly expensive. Hard to make and doesn’t have all that much use, I’m guessing.

There’s no real reason why you can’t use (vacuum proof) glass all the way, except for the reactor itself, right?

What pressure did you operate at? My experience with vacuum is really limited, so that would be a learning curve with some much needed dry runs.

Tantalum? What did you try? I’m guessing reduction of Ta2O5 with Mg, boosted with strong preheating, could achieve the MP of Ta.




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[*] posted on 4-12-2011 at 11:43


That's an interesting point you raise. The reaction may proceed fastest at around 600 or above but below the softening point of Pyrex ( I think I remember a figure of about 550 as the service ceiling...don't quote me on that) the reaction doubtlessly proceeds. A small metal cup with reactants contained within a glass apparatus was actually mentioned in the literature...somewhere. Sorry I can offer no further details, it's something I read but didn't save.

My pump is a Hitachi 160VP Cutevac rated at a pumping speed of 174 L/min and an ultimate vac. of 0.01 Pa. Pumping speed is kind of unimportant with a small aparatus. This is WAY more than needed. The vacuum converts to 7.5 x 10 to the -2 mmHg.

New reactor:http://tinypic.com/r/izrme0/5

Pump:

The Ta was made via Na + K2TaF7 in a steel bomb evacuated by an aspirator and welded shut. I believe the reaction proceeded ok but the rxn. produces a powder.
Never having an inert gas meant every attempt at consolidation by heating a pressed compact failed. It just wasn't worth getting the gas for. It was a half-failure perhaps.


[Edited on 4-12-2011 by Zan Divine]
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[*] posted on 4-12-2011 at 12:54


I wasn’t really thinking of a glass reactor, just glass for anything downstream from it: that would save on one glass/metal joint.

So 0.075 mm Hg, on average slightly above values reported in the patent (I’m surprised this could be patented at all: there’s really nothing particularly new about the idea).

K2TaF6 reduced with sodium will give you powder, of course.

PS: you’ve just committed your first cardinal sin ;) here: an oversized photo!



[Edited on 4-12-2011 by blogfast25]




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Zan Divine
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[*] posted on 4-12-2011 at 16:40




These are a couple ampoules I made up by melting the Cs under mineral oil and pipetting in air into open amps.
The tips of the pipettes smoked during transfer. Evacuated amps. and sealed under a vacuum. This is nothing more than a crude first attempt. Quality will improve with Argon.

The pipettes are on my patio being exposed to air/moisture slowly. If you throw them into water they will likely break. Reaction with H2O is SO VERY VIOLENT. Do not EVER warm or cool glass containing Cs with a water bath. I just can't stress enough how much worse the reaction with water is than K and water. I use cold sand for cooling and warm air for heating. When Cs burns in air it's not very different from K..... but the reaction with water...!!!!

[Edited on 5-12-2011 by Zan Divine]
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[*] posted on 5-12-2011 at 07:19


This is the only video I know of that shows the reaction with water of Li, Na, K, Rb and Cs in comparable conditions. Cs is the only one that manages to shatter the glass container. This one excels in clarity. Water and cesium really don’t mix. And this one’s Cesium porn but no water. (But I’m sure you’ve watched all of these before)

I’m getting concerned for my fellow forum members: someone displays ampoules of home made Cs metal and they don’t lign up to come and see them?!? Wakey, wakey, chaps! Something interesting's hapening here!




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[*] posted on 5-12-2011 at 09:05


Interesting

Our very own len1 synthesised cesium by heating CsCl with calcium under vacuum at 640 - 700 C. This was described in his book "small-scale synthesis of laboratory reagents"

Cesium.jpg - 87kB
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[*] posted on 5-12-2011 at 10:51


Extremely interesting synthesis, congratulations! Seems a lot easier than I would expect for something like cesium.

In that last picture of the two ampoules, are they both cesium? The one on the left looks very distinctly silver instead of gold. It looks a lot more like one of the other alkali metals than cesium.
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Zan Divine
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[*] posted on 5-12-2011 at 11:08


Calcium was my second choice. Due to lithium's higher % yield and the fact that it would be liquid at the rxn. temp and Ca wouldn't, I chose it for the reductant. The Cs in this run was made using the Li from 2 size AA lithium batteries. This lithium is not exactly the cleanest available but it worked well enough.

Blogfast, thanks for the links. I had only seen the first one previously. I apologize for looking past your earlier question of amount. I had no intention of quantifying this run. In my estimation it must have been 6-7+ grams in the flask and another half a gram or so hung up in the glassware. When I get the argon cylinder more quantitative results will follow.

MrHomeScientist, Thank you and they are both cesium. The stuff degrades before your very eyes though. Even the dissolved oxygen in mineral oil quickly attacks it. Don't read too much into the color. Cs is silver just like the others. Trace oxygen contamination causes a golden hue to be displayed. The golden color is just part of the element's mystique. People want to believe it's intrinsic, but it really isn't.

I have no doubt at this point that making Cs is the easy part. Effective packaging of clean material will be harder.

[Edited on 5-12-2011 by Zan Divine]
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[*] posted on 5-12-2011 at 13:00


Quote: Originally posted by Zan Divine  

I have no doubt at this point that making Cs is the easy part. Effective packaging of clean material will be harder.

[Edited on 5-12-2011 by Zan Divine]


Yep. Packing in completely inert atmosphere seems to be the only possibility I think. Start thinking 'airtight positive argon pressure glove box'! I can't see how it can be done safely and without sample corrosion otherwise. It's something that will increase the cost very considerably.

[Edited on 5-12-2011 by blogfast25]




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[*] posted on 5-12-2011 at 15:12


Interestingly, I'm in charge of installation & servicing for our company in the US....our product? Gloveboxes.

Just bought an S cylinder of argon. Let's see how well a good quality glovebag works.

Strategy for next prep:
1) Rigorously clean inside of apparatus.
2) Obtain clean Li (in progress)
3) Size reaction and receiver so that the small round-bottom is full at the end.
4) Separate product flask, purge head space with argon.Stopper.
5) Into the glovebag. Cs withdrawn from below surface of sample and loaded into ampoule....etc.

I think I'll do the next reaction with the aim of producing about 18 grams which will fill a 10 mL 14/20 rb.

I'll keep you posted. Meanwhile business travel will eat up a number of upcoming days so it won't be real soon.
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[*] posted on 6-12-2011 at 08:46


Remember that your bunsen or propane torch won't be of any use inside an argon filled glovebag or glove box, Just one more of these nagging problems :(



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Zan Divine
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[*] posted on 6-12-2011 at 09:23


What I use as a sealing technique is to put a compressed pipette bulb over the end of the ampoule. As it tries to expand it pulls just the right negative pressure on the ampoule to allow easy sealing. I'm sure I can bring them out and seal them cleanly at that point.
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[*] posted on 15-12-2011 at 21:25


This may be new to the foum...

Attachment: Rb & Cs from the chlorides.pdf (1MB)
This file has been downloaded 359 times

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[*] posted on 17-12-2011 at 06:15


Well, there you go: the answer to all your packing problems without a glovebox! ;)



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[*] posted on 21-12-2011 at 20:49


This is a shot of the metal from my first production run. Pre-drying of the reactor, flame drying of the glassware and argon for the necessary blanketing during loading and unloading helped produce nice clean metal in 77% yield @ the 50 g (CsCl) scale. Yield is a bit lower than reported (90-98%).

As soon as I get my oxygen cylinder refilled, I'll be good to go with ampoules.

clean sm.jpg - 68kB

[Edited on 22-12-2011 by Zan Divine]
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[*] posted on 22-12-2011 at 06:45


Wunderbar!

Where did you get your Li from this time? Still virgin Li batteries?

I look forward to your experiences with a (plastic?) glovebag and a burner to seal the ampoules! ;)




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[*] posted on 22-12-2011 at 07:47


I bought the Li this time, from GalliumSource in Ca. I've never found a better source for Li, Na or K than these guys. They pay the Hazmat fee and prices are very reasonable.

Now that the metal is clean, I'm rethinking my handling plans. Realistically speaking, I may get the glovebag atmosphere clean enough to handle the molten metal, but maybe not. So, given the ease of keeping Cs liquid, I'm wondering if an all-glass syringe, similar to those I've always used to transfer organolithium reagents, might not be the best strategy. Simply prepare argon-filled ampoules with rubber septa, and use the syringe to transfer from a septa-sealed flask of Cs under a slight positive pressure of Ar. The only exposere to air would come at the very tip of the syringe needle and hopefully any oxide, hydroxide or possible (?) nitride would be wiped clean upon piercing the septa on the ampoules.

Considering all the factors, I can probably get a cleaner product this way.

I cannot, unfortunately, redistill the metal in an all glass apparatus. This requires a better vacuum than I can attain. The original workers used diffusion pumps to get there. The original paper I worked from (the patent) claimed 99% purity as singly distilled. I've seen commercial samples that analyze at 99.5% and they, too, wet glass like mine. Only redistilled material above 99.5% (typically 99.9%) beads up on glass. surfaces.

This marks an accetible compromise to me. Only with additional manpower, equipment & time could I go from 99% to 99.9% and, truthfully speaking, collectors are forced, more commonly than not, to accept group 1 metals with relatively thick oxidation layers. Except in an ampoule, who ever sees bright silver, shiny K? Or Na (for more than tens of seconds, anyway)?

This material is bright and shiny, slightly golden-hued due to imperfect O2 exclusion, and I think this is a good compromise.

It kills me that my O2 cylinder will be out for weeks. I sent it for hydrostatic testing with the refillers....out of state! I had no choice. It's been > 10 years since the last one and they tell me that I'm not allowed to own a K cylinder and they won't simply swap for a full one. They will, however, refill the one I "own" ( It's been in my posession >15 years. You're damn right I own it insofar as no company is going to get it back only to charge me $5 rental/month). Legal disclaimer...this paragraph is fantasy. No responsible person would keep one of their cylinders just to save $60/year....would they?
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[*] posted on 23-12-2011 at 06:46


That makes sense, Zan. You could flush the syringe too, I guess. For 99 % Cs that should really be sufficient and a lot less messier than glove boxes or glove bags...



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[*] posted on 23-12-2011 at 19:15


Welcome to the cesium club! As congratulations, I can send you RbCl so that you can make that as well. I have a 50 or 100 g bottle to spare. I have a spare diffusion pump too, as well as a kg or two of CsCl; what I don't have these days is the time!

Your apparatus is VERY similar to what I have used, except I used SS316 for the 24/40, a tube furnace, and a sealed swagelok 1" tube.

You may consider a distillation receiver that allows for vacuum and argon to be applied.

If I do it again, I'll try with lithium (although I worry more about the purity with lithium than with Ca).





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[*] posted on 24-12-2011 at 05:27


Was your lithium a block, foil, powder? Did you just put in the CsCl and drop the lithium block on top?
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