Sciencemadness Discussion Board

Cesium from CsCl

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MyNameIsUnnecessarilyLong - 5-6-2012 at 23:34

Does anyone know how reactive cesium vapor is to copper metal? What about cast iron?


I wanted a wide opening on my chamber for easier loading and cleaning, so instead of using threaded fittings I think I'll just make some knife edge vacuum flanges to couple a condenser assembly to the reaction chamber and have it seal against a copper gasket.

If copper isn't compatible enough then I guess I could make the flanges to be a taper seal and use a soft iron ring instead... But would it be able to deform enough to create a tight vacuum seal?

Zan Divine - 6-6-2012 at 06:46

Copper doesn't react with cesium, and although cesium will likely erode copper over time, attack is slow enough.

Cast iron will also stand up to cesium. Cesium probably will pull certain trace elements out of the iron, hopefully these should (mostly) remain behind during distillation.

All in all, Cu is by far the better choice. Even then, I expect the seal to give you fits if you actually test it out. You should strive for 0.001 mm Hg for the best results. Even though this process can even be done at 10 mm Hg, a good vacuum seems to give a cleaner product as judged by the amount it wets glass. A better vacuum also makes the necessary distillation temperature 100 - 200 degrees C lower.

Pipe threads are actually kind of poor at holding a good vacuum without thread sealant, and few sealants are good at these temperatures. Your move to escape these damned leaky little grooves is a really good idea. The devil, of course, is in the details.

I can't explain it but, in the cases where I collected fractions, the later fractions also appear cleaner (by the same criterion as above). I would have expected the opposite based on the likely contaminants being Li as well as perhaps Rb from the CsCl and Na in the Li. The likely contaminants should be less volatile than Cs, I would have guessed.

In my experience, loading and cleaning are easily done through a 1/2 to 3/4 inch opening. Cleanup is especially easy since everything dissolves in water with varying degrees of excitement.

Remember to put a small wad of steel wool (SS is better still) at the top of the reactor to prevent physical bumping from carrying impurities into the condenser tube.




[Edited on 6-6-2012 by Zan Divine]

MyNameIsUnnecessarilyLong - 8-6-2012 at 20:19

This is the general design at the moment based off what materials I already have on hand:





I'm thinking the best way to avoid cesium getting stuck within the coupled area will be to turn a chamfer inside until the radius almost meets the copper ring. Then for the upper flange I'll give it a chamfer and then weld a shroud/flare around that which can nest virtually metal-to-metal against the lower chamfer so that when the whole thing is brought up to temp the thermal expansion can swage this cone against the chamfer. This should, hopefully, both funnel the cesium vapor into the condenser and also stop any liquid cesium or cesium vapor to come in contact with the copper gasket.

The extra space between the chamfers should also help contain any bumped material






And here's what I have so far:




The heating filament needs to go since it's not fitting inside the heat shield/stand. I wanted to use a bendable heating element that hardens to shape after first use, but there's only about 3/16th - 1/8th clearance for the last 1/2" of the chamber between the heat shield. The smallest dia element I've found is about 1/4". Will probably end up using some of that alumel wire or high temp heating tape





This is the Welch 1376 style vacuum pump I'll be using:



This beast weighs ~150lbs! :mad:
Way too heavy IMO when it only pulls down to 1 x 10-4 torr.

[Edited on 6-9-2012 by MyNameIsUnnecessarilyLong]

Zan Divine - 9-6-2012 at 08:35

Verry nice! Good welding skills, too.

With your very good vacuum, you'll possibly be able to get down to the region where flexible heating tapes will work but I strongly advise against it. They were never meant for this temp. regime.

Any of the resistance wires can operate here, the insulation is the trick. Fish spline beads (also as fish spine beads) are sold at numerous outlets. Below is a picture of the 4.3 mm OD beads and the 0.8 mm Alumel wire I used. This is the ideal answer to the need to wrap flexible heat around a metal tube.

The metal shroud around the outside of the heating unit is beautiful but may be counter-productive. It won't reflect much heat inward but will conduct much heat outward (even if it's SS). Do yourself a favor and buy some of the bio-soluble ceramic fibre board in the low temp version. You can cut it with a knife, glue it with furnace cement and it is perfect for this application.

Your initial distillate will wet glass almost certainly. You'll need to redistill. See my earlier posts for literature preps & purification if you haven't yet.

Don't forget the argon. Welding gas, as you know, can be up to 1% O2. Use UHP if you can. If I blow my welding grade argon over molten K the surface darkens somewhat.

For moderate flow rates, welding argon, which is bubbled through a short column of NaK alloy, will do.

DSCN0826.JPG - 217kB



[Edited on 9-6-2012 by Zan Divine]

watson.fawkes - 9-6-2012 at 08:42

Quote: Originally posted by MyNameIsUnnecessarilyLong  
This is the Welch 1376 style vacuum pump I'll be using: [...] Way too heavy IMO when it only pulls down to 1 x 10-4 torr.
There are two figures of merit for vacuum pumps: ultimate pressure and pumping rate. A pump of that size has a rather large pumping rate. It could be used quite successfully to back up a diffusion pump.

watson.fawkes - 9-6-2012 at 08:44

Quote: Originally posted by Zan Divine  
Fish spline beads (also as fish spine beads) are sold at numerous outlets. Below is a picture of the 4.3 mm OD beads and the 0.8 mm Alumel wire I used. This is the ideal answer to the need to wrap flexible heat around a metal tube.
Another method is to adhere ceramic paper with sodium silicate directly onto the chamber being heated. After that, resistance wire can be coiled directly onto the surface. A second layer of paper/silicate holds the heating element in place.

blogfast25 - 9-6-2012 at 10:20

How will the metal cooler (I presume) be successfully coupled to the glass receptor?

MyNameIsUnnecessarilyLong - 9-6-2012 at 13:16

Quote: Originally posted by Zan Divine  
Verry nice! Good welding skills, too.

The metal shroud around the outside of the heating unit is beautiful but may be counter-productive. It won't reflect much heat inward but will conduct much heat outward (even if it's SS). Do yourself a favor and buy some of the bio-soluble ceramic fibre board in the low temp version. You can cut it with a knife, glue it with furnace cement and it is perfect for this application.


I wish I could claim those welds! :mad: These cones were fabricated for a local medical research institute. I'm only using it because I've had several of them laying around for years. It does look nice but if it's too problematic then I wouldn't mind replacing it.

Quote:
Don't forget the argon. Welding gas, as you know, can be up to 1% O2. Use UHP if you can. If I blow my welding grade argon over molten K the surface darkens somewhat.

For moderate flow rates, welding argon, which is bubbled through a short column of NaK alloy, will do


Do you think those argon cartridges for preserving wine are pure enough? I'd rather not buy a new tank or refill one right now. Or bubble through precious NaK :o



Quote: Originally posted by blogfast25  
How will the metal cooler (I presume) be successfully coupled to the glass receptor?


I'll be machining the taper at ~70 degrees (temp) and pass air over it during distillation to keep it from expanding or contracting beyond what it was machined at. And it'll be used with grease or sleeves of course.

If that doesn't work out, then since there really won't be high temps involved at that end, I could always put a couple o-ring grooves on the taper and have these seal it.



I would actually like for the cesium to collect directly into an ampoule so that it can be flame sealed on spot instead of transferring and flushing with argon. Hmmm... Anyone got ideas on how I could set this up?



Quote: Originally posted by watson.fawkes  
Quote: Originally posted by MyNameIsUnnecessarilyLong  
This is the Welch 1376 style vacuum pump I'll be using: [...] Way too heavy IMO when it only pulls down to 1 x 10-4 torr.
There are two figures of merit for vacuum pumps: ultimate pressure and pumping rate. A pump of that size has a rather large pumping rate. It could be used quite successfully to back up a diffusion pump.


But for such a small chamber how much does the flow rate really matter?


Speaking of diffusion pumps, I have a little Veeco diffusion pump booster like this one that's kicking around somewhere:



Except I have no idea how to install it. How much vacuum do you think this would pull when used along with my Welch pump?

[Edited on 6-10-2012 by MyNameIsUnnecessarilyLong]

Zan Divine - 10-6-2012 at 07:51


Do you think those argon cartridges for preserving wine are pure enough? I'd rather not buy a new tank or refill one right now. Or bubble through precious NaK :o

Well, probably not. But that's a guess as I'm not familiar with the product.

Here's Cs's dirty little secret, though....Cs is actually the same color as the other group 1s, bright silver. Cs forms a multiplicity of oxides. One or more of them cause the golden tint associated with Cs. So, your atmosphere doesn't need to be perfect, just good.

VERY IMPORTANT: Don't use your inerting gas in a flow-through configuration. Just apply the blanket to the vacuum of the reactor (and subsequent vessels) and keep it static.


If that doesn't work out, then since there really won't be high temps involved at that end, I could always put a couple o-ring grooves on the taper and have these seal it.

Needs good execution to seal well, but I see you've got the skills. The surface finish of the grooves should be very smooth.
Supplement with thin grease film.

I would actually like for the cesium to collect directly into an ampoule so that it can be flame sealed on spot instead of transferring and flushing with argon. Hmmm... Anyone got ideas on how I could set this up?

I can give you diagrams. I thought I had uploaded this stuff a few pages back, but maybe I'm mistaken. You'll need glassblowing skills.

If you just want one big ampoule under vacuum, simply glassblow a female ground glass joint on to the top of your ampoule. Make the constriction carefully. It needs to be sealed under a full vacuum. If Cs wets the constricted area, use gentle flame heating to evaporate it away before sealing. This is all or nothing time, if you have a blow-in, it's very unfortunate.

I prefer sealing under argon. You can just fill the above described ampoule with argon at slightly reduced pressure and it is much safer. Hard to avoid using argon in this work.


But for such a small chamber how much does the flow rate really matter?

Not at all, almost. He was just explaining why your pump was large.

Speaking of diffusion pumps, I have a little Veeco diffusion pump booster like this one that's kicking around somewhere:
IMG
Except I have no idea how to install it. How much vacuum do you think this would pull when used along with my Welch pump?

It goes between the roughing pump and the system. Vacuum depends on the medium. Oil pumps will increase your vac by an order of magnitude, roughly speaking, given your starting vacuum. Hg pumps are less effective. I can't really tell much about your unit from the picture.

Your good vacuum will allow you to redistill from pyrex. Your purity will increase and the Cs will wet glass less. One source claims that after another redistillation you'll achieve the 99.9 or 99.9+% purity necessary to make Cs non-wetting to glass.

It sounds, and is, tedious. Your distillations should proceed quite rapidly, though, which helps.

It will make your final product much more appealing. I'd do it with mine if I had the equipment.


[Edited on 10-6-2012 by Zan Divine]

blogfast25 - 10-6-2012 at 09:58

Quote: Originally posted by Zan Divine  

Do you think those argon cartridges for preserving wine are pure enough? I'd rather not buy a new tank or refill one right now. Or bubble through precious NaK :o



I doubt that too. That's low grade argon. Pull it over an oxygen getter.

MyNameIsUnnecessarilyLong - 10-6-2012 at 16:27

Lots of helpful info here, thanks Zan.


Quote: Originally posted by Zan Divine  

I can give you diagrams. I thought I had uploaded this stuff a few pages back, but maybe I'm mistaken. You'll need glassblowing skills.


I saw your glass contraption for purifying and ampouling Na, K. Is this the same device you're talking about?

I don't think I could fuse the two ends without constricting the neck too much. I'm using commercial pre-scored 5mL ampoules with bottle necks rather than straight tubing. The inner dia of the neck on these is only about .31"

Quote:
I prefer sealing under argon. You can just fill the above described ampoule with argon at slightly reduced pressure and it is much safer. Hard to avoid using argon in this work.


Yeah, I don't like the idea of sealing (or keeping) ampoules under heavy vacuum either. I was actually thinking that after the reaction-distillation completed, I would raise the pressure a bit first by bleeding in argon and then sealing the collection ampoule.



Quote:
Your good vacuum will allow you to redistill from pyrex. Your purity will increase and the Cs will wet glass less. One source claims that after another redistillation you'll achieve the 99.9 or 99.9+% purity necessary to make Cs non-wetting to glass.



Hmm, I thought even at that vacuum the cesium wouldn't vaporize before the critical point of the glass. Does anyone have a phase diagram of cesium?

Hell, if that's the case then I should just do the whole reaction in a glass apparatus!

[Edited on 6-11-2012 by MyNameIsUnnecessarilyLong]

Zan Divine - 10-6-2012 at 16:47

Download the file I posted on 12-15-11, Rb and Cs from the chlorides.

This is a gold mine of information. Such as when and how you can distill from glass.

You can't do the reaction in glass. Nobody even tries. Even though there is no apparent source for it, more than one prep. mentions the evolution of gas during the reaction. The vacuum during the synthesis won't be good enough to allow you to distill from glass.

Since I've recently faced a lot of the problems you'll face, I suggest you scan my posts since Dec. I hope they'll save you some effort.

Commercial ampoules have relatively thin walls. It's extremely difficult to join them to heavier glass. I'd consider making an ampoule from medium wall tubing. Remember to make it a bit long if you ever intend to open it.




[Edited on 11-6-2012 by Zan Divine]

Zan Divine - 11-6-2012 at 18:32

As I examined the reactor, something caught my eye.

You can't have a lot of thermal mass directly above the reactor. If the head is a lot cooler than the area below it, it will cause metal vapors to condense and run back down into the reactor(reflux).

The exact taper for making a metal joint can be easily looked up. I can tell you by examination of your apparatus that the metal joint won't expand enough to be a problem.

MyNameIsUnnecessarilyLong - 11-6-2012 at 18:56

Quote: Originally posted by Zan Divine  
As I examined the reactor, something caught my eye.

You can't have a lot of thermal mass directly above the reactor. If the head is a lot cooler than the area below it, it will cause metal vapors to condense and run back down into the reactor(reflux).



I thought about this. But I figured if I made the elbow/down-stem as close to the chamber as possible, that enough cesium would still be able to make it past the bend. The heat shield/cone might help to warm the lower flange, at least.

But would the addition/slower removal of cesium change the reduction equilibrium? I wouldn't mind if it simply required longer distillation times, but if the yield plummets...


A different reactor I was planning involved immersing the reactor and part of the condenser inside an annealing oven to give controlled and uniform heating. The condenser would stick out through a hole in the side of my oven where the thermocouple/peep hole goes. I could do the same thing to this one by throwing it in the oven, but that really defeats the purpose of the design of a stand-alone, plug-it-in cesium still...

[Edited on 6-12-2012 by MyNameIsUnnecessarilyLong]

blogfast25 - 12-6-2012 at 05:38

Quote: Originally posted by Zan Divine  

You can't have a lot of thermal mass directly above the reactor. If the head is a lot cooler than the area below it, it will cause metal vapors to condense and run back down into the reactor(reflux).



Preheat the reactor top, prior to loading, assembly and reaction, then keep a hairdrier pointing to it? 'Medium curls' should do it! ;)

Zan Divine - 12-6-2012 at 14:05

But seriously though, don't underestimate this point. Note the emphasis placed on this point on pp 962-963 by Donges in that reference.....

The equilibrium will go where it will go, the rate of take-off should have little effect on this...but...this is the ideal situation. In reality time is not your friend, you will have various processes working against you. The inevitable result of this design will be a lower yield, IMHO.

The idea of putting everything into the furnace is much better. I guarantee that it will work better.

blogfast25 - 13-6-2012 at 04:13

Do we know the BP of Cs in these conditions?

Your point is valid, Zan. Just a simple plate as reactor top would be better. Or tapering of towards the top (instead of the reverse) must be better too.

Zan Divine - 15-6-2012 at 13:26

Cs bp (760 mm) is 671 degrees C

P-T Nomograph gives a bp of 392 C @ 1 mm Hg, 336 C @ 0.1 mm Hg and 297 C @ 0.01 mm Hg.

These numbers suggest that borosilicate and a standard oil-filled lab pump are sufficient to redistill. I guess I will try this after all.



[Edited on 15-6-2012 by Zan Divine]

blogfast25 - 16-6-2012 at 04:50

Quote: Originally posted by Zan Divine  
Cs bp (760 mm) is 671 degrees C

P-T Nomograph gives a bp of 392 C @ 1 mm Hg, 336 C @ 0.1 mm Hg and 297 C @ 0.01 mm Hg.

These numbers suggest that borosilicate and a standard oil-filled lab pump are sufficient to redistill. I guess I will try this after all.


[Edited on 15-6-2012 by Zan Divine]


Thanks, Zan, very interesting. Book marked.

[Edited on 16-6-2012 by blogfast25]

Zan Divine - 16-6-2012 at 06:50

Funny thing, blogfast, is that I actually bought the extra glassware needed to redistill this way and planned to do it. As time passed, my recollection seemed to be that it would be pushing the envelope.

Now that I've actually looked at it again, thanks to your querry, It seems to be well within the borosilicate realm. Still, I'm glad the distillation pot will be buried in alumina powder inside the confines of the furnace.

Zan Divine - 22-6-2012 at 07:29

I did another of these MCl reductions last night.

It made me remember exactly how powerful the cooling effect of the metal above the reactor is on influencing distillation rate. Even with my tiny thermal mass, warming with a propane torch was needed to stop refluxing and promote distillation.

If you leave your present reactor out of the oven, you'll NEED a propane torch to do the same.

Zan Divine - 27-6-2012 at 12:06

Well, to wrap up my progress here I'll post this final picture of my recent Cs ampoules. I can now make them without any traces of oxide. Not surprisingly it a matter of learning a few little tricks, but the most important seemed to be to freeze the Cs before sealing the ampoule.

cs3 (Small).jpg - 79kB

[Edited on 27-6-2012 by Zan Divine]

Sublimatus - 27-6-2012 at 15:31

That's the first sample of silvery caesium I've ever seen. It's beautiful. :o

Do you think it'll tarnish if it were to remelt inside the ampule?

In any case, congratulations.

Zan Divine - 27-6-2012 at 16:01

Thanks. The metal remains totally shiny when melted. It looks like clean mercury but with a golden tint. It won't change since it's under argon and any adventitious oxygen has already reacted.

Sublimatus - 27-6-2012 at 16:21

Excellent.

Now if only shipping rates weren't so absurd for some of the more interesting elements...

mr.crow - 27-6-2012 at 19:45

Zan Divine, you are a hero!

elementcollector1 - 13-8-2012 at 21:10

I hate to ask this again, but it has been quite a while, so... How could I get my hands on a small amount of elemental cesium?

Zan Divine - 14-8-2012 at 05:26

Cesium is available on e-Bay currently.

[Edited on 8/14/2012 by Zan Divine]

haroldramis - 15-8-2012 at 18:28

They look nice.
I never heard of the 1g exemption though. Do you have a link or reference for it? I remember last time you tried to list it was de-listed as there were shipping issues.

Zan Divine - 17-8-2012 at 14:43

Quote: Originally posted by Zan Divine  
Cesium is available on e-Bay currently.


...and now it's gone.

Sublimatus - 17-8-2012 at 14:47

All bought, or forcibly removed?

Zan Divine - 17-8-2012 at 15:01

Sold to forum member off e-Bay.

Actually, both (I only advertise 1 at a time on e-Bay).

More ampoules will likely take time. Ripped a calf muscle and I'll be in a cast after surgery. Getting my exhausted O2 cylinder out of the basement and refilled is a task even with both legs. So, unless and until I get someone to do this, no ampoules can be made.

[Edited on 8/17/2012 by Zan Divine]

elementcollector1 - 17-8-2012 at 16:41

Ouch! We can wait for the cesium, then.

BromicAcid - 17-8-2012 at 19:36

Quote: Originally posted by haroldramis  
They look nice.
I never heard of the 1g exemption though. Do you have a link or reference for it? I remember last time you tried to list it was de-listed as there were shipping issues.


173.4b De minimis exceptions.

Quote:
(a) Packing Group II and III materials in Class 3, Division 4.1, Division 4.2, Division 4.3, Division 5.1, Division 6.1, Class 8, and Class 9 do not meet the definition of a hazardous material in §171.8 of this subchapter when packaged in accordance with this section and, therefore, are not subject to the requirements of this subchapter.

(1) The maximum quantity of material per inner receptacle or article is limited to—

(i) One (1) mL (0.03 ounce) for authorized liquids; and

(ii) One (1) g (0.04 ounce) for authorized solid materials;


This is the regulation that a DOT rep quoted me when I asked if I could have a vial of bromine hanging from my rear view mirror back when I was attending hazardous waste conferences. Although with some of the other stipulations written in the remainder of the reg I have my doubts if a glass vial hanging from a mirror would really pass the test although let's face it, not many people would recognize it for what it was.

Edit: Looked up cesium in the shipping table, it's actually a packing group I so this wouldn't apply. Then again, so is bromine.

[Edited on 8/18/2012 by BromicAcid]

elementcollector1 - 17-8-2012 at 21:12

Haha, I'd love to see that car.

elementcollector1 - 1-2-2013 at 09:48

Topic bump! Anyway, I was wondering: What are the major difficulties of distilling cesium? Namely, if I welded together a good steel reactor for distilling with lithium from batteries, or pure sodium / magnesium / calcium (depends on which works best), and connected that to a glass receiving tube under vacuum (what strength vacuum to use? I'm assuming pretty high), and simply melted the end of the tube off so as to make an ampoule, would that work? Or are there things I've not considered here? First things first, to get some cesium compounds.

blogfast25 - 1-2-2013 at 10:20

EC1:

Everything you need to know is really in this thread. I suggest you print it off and as the man says because this is no sinecure if you haven't done it before!

'Roger' to getting reasonably priced CsCl (all the others need messy conversions): that's the first serious hurdle!

MyNameIsUnnecessarilyLong - 1-2-2013 at 19:06

Quote: Originally posted by elementcollector1  
connected that to a glass receiving tube under vacuum, and simply melted the end of the tube off so as to make an ampoule, would that work? Or are there things I've not considered here?


I created an o-ring adapter for connecting ampoules directly to my condenser. The neck on these ampoules should be long enough for me to pull it out (after the cesium drains from the condenser) to near the front o-ring then melt and squeeze it shut. I haven't got around to testing it yet, though. After I made it I got a feeling that the thin-walled ampoules I'm using might cave in at the molten areas under high vacuum. Thick-walled tubing probably wouldn't have this problem, and that's probably what you should go with if you do at all.



http://i47.tinypic.com/2cfqt6g.jpg

http://i45.tinypic.com/eb6fix.jpg

elementcollector1 - 1-2-2013 at 21:21

Is steel required for the receiving end? I seem to remember the cesium-pioneers on this forum using glass.

MyNameIsUnnecessarilyLong - 1-2-2013 at 21:34

Quote: Originally posted by elementcollector1  
Is steel required for the receiving end? I seem to remember the cesium-pioneers on this forum using glass.


Glass is fine. The hard part is connecting it to the reactor, which has to be steel/stainless/iron. Zed accomplished this by using a metal taper to glass joint. If you go with a metal taper, the neck needs to be long enough so that the taper itself won't heat up from the cesium or heat of the reactor.

elementcollector1 - 1-2-2013 at 21:47

What about the condenser; can this be glass as well? Again, according to Zan's original setup, it does work (although again, there is that metal taper to think about)...
Also, will a hand vacuum pump be any good for the vacuum required, or will a real pump be necessary?

blogfast25 - 2-2-2013 at 08:13

EC1:

From this thread:

http://www.sciencemadness.org/talk/viewthread.php?tid=6981&a...

Pressure ranged from 0.005 to 0.07 mm Hg, although one specific run stands out at 700 mm Hg (and still yields about 50 %!)

The kind of vacuum pump used by Zan is a couple of posts below that one. Higher vacuum makes distilling the Cs metal easier.

elementcollector1 - 10-6-2013 at 11:51

So, according to that, more vacuum = more %yield, instead of high vacuum = results.

If I get an aspirator (and presumably do something to prevent the water running through it from vaporizing and hitting the cesium, though I don't know what - more dry CsCl in a trap, so the Cs won't react?), I apparently get down to 23-24 torr just from water (which, while not being quite so good as the vacuum pressures listed, should work).

A hand pump apparently will only pull a measly 620 torr, not nearly good enough for my standards even if it does remove the dangers of water vapor.

Vacuum pumps? Far too expensive, and not even the school lab has one. The university has them, but I don't know what those pull (and even if I did, there's no way they'd let me borrow one).

blogfast25 - 11-6-2013 at 03:57

Yes, but I'd go with the highest vacuum possible, if given a choice.

Dan Vizine - 17-4-2014 at 19:37

I am, btw, Zan. Another batch of Cs will be whipped up soon and it will be the purest yet as the reductant is 99.8% Ca (same as my ThO2 redn.)

What's expensive, really? Look at what you gain. Your time is neither endless nor free. The vacuum pump is one of the most important items in any synthetic lab. I got mine on eBay for $80 shipped, an untested unit. The main shaft seal is leaky, so what? The vac. is 0.002 mm Hg. I can recycle the filtered oil. Someday I'll find the time to replace it.

elementcollector1 - 17-4-2014 at 20:44

$80? Lucky. I think I will try first with the aspirator pump and a drying agent - but that's after I get the setup finished!
I now have access to (but not ownership of) welding equipment, so I'll see if I can get something put together.

Dan Vizine - 18-4-2014 at 06:03

Remember you need a fail-safe back flow preventer in the vacuum line. City pressure varies and when you are already pulling the best vacuum that your aspirator can, and water pressure drops because of demand changes elsewhere, water quickly backs up into the device under vacuum.

Also, welding ends onto SS pipe is very difficult. The coefficient of thermal expansion is large and cracks and pinholes are common. I brought half of a lecture bottle to a professional welder. He tried to weld a 316 bottom on. He failed to achieve gas tightness just as I had a half dozen times earlier. The composition of this bottle, which held NOCl previously, was unknown.

If you are operating at 10 mm Hg you could save lots of work by using common plumbing fittings. If you prefer to weld stick to mild steel.

[Edited on 18-4-2014 by Dan Vizine]

Dan Vizine - 18-4-2014 at 09:38

Here's an idea. To transit from pipe to glass, just use a rubber stopper. Make sure the metal tube sticks out 1/2 inch past the bottom of the stopper. The stopper holds vacuum just as well as your rubber vacuum hose. The more I play with it, the easier it gets to make an apparatus, that functions well, out of simple materials.

Incidentally, for $40 you can buy a pre-manufactured 300 mL SS reactor on eBay right now.

http://www.ebay.com/itm/191081558900?ssPageName=STRK:MEWAX:I...

Unless you value your time at less than a few dollars per hour, how can you beat that?

Also, the price of CsCl 99.9% or better is about $40/100g because ppl. use it as a putative cancer treatment. Google it and you'll have no problems.

Dan Vizine - 18-4-2014 at 09:45

Quote: Originally posted by MyNameIsUnnecessarilyLong  
Quote: Originally posted by elementcollector1  
connected that to a glass receiving tube under vacuum, and simply melted the end of the tube off so as to make an ampoule, would that work? Or are there things I've not considered here?


I created an o-ring adapter for connecting ampoules directly to my condenser. The neck on these ampoules should be long enough for me to pull it out (after the cesium drains from the condenser) to near the front o-ring then melt and squeeze it shut. I haven't got around to testing it yet, though. After I made it I got a feeling that the thin-walled ampoules I'm using might cave in at the molten areas under high vacuum. Thick-walled tubing probably wouldn't have this problem, and that's probably what you should go with if you do at all.



http://i47.tinypic.com/2cfqt6g.jpg

http://i45.tinypic.com/eb6fix.jpg


You're right. They collapse very easily. A deft touch and a really small torch (like the butane-oxygen models by Archer @ Radio Shack. IF they still carry them) are best. This is not easy. Highly suggest glass tubing. Much more durable too.

Oh, and another thing...the Cs will wet glass. You'll have trouble sealing any glass over which the molten metal flows. That's why I collect in one thing and use syringes (plastic) to move the Cs around for sealing.

[Edited on 18-4-2014 by Dan Vizine]

elementcollector1 - 18-4-2014 at 19:17

Why not combine both ideas and include a sort of drip tube that centers the caesium distillate so it drops into the center of the ampoule?

Dan Vizine - 19-4-2014 at 07:10

Good point. In fact, that is what I use for the distillation, a vacuum take-off adapter with a drip tip. Everywhere it touches more glass you'll lose material. That's why I went to plastic syringes instead of glass.

DON'T try to seal the ampoule connected to the apparatus while it is still hot. If you have a "blow-in" it will be very unpleasant.

Is the intention to make a single ampoule containing the entire produced amount?

But anyway, I still strongly suggest glass tubing for the ampoule. If you look at various "large" Cs ampoules from the internet (the 99.99%) kind, they use cylindrical tubing with rounded bottoms not the thinner kind with flat bottoms.

Btw, do you have any sort of inert gas available? It REALLY helps.

elementcollector1 - 21-4-2014 at 09:27

Quote:
DON'T try to seal the ampoule connected to the apparatus while it is still hot. If you have a "blow-in" it will be very unpleasant.

Good to know... Although knowing caesium, I would certainly wait until it cooled before doing much of anything!

Quote:
Is the intention to make a single ampoule containing the entire produced amount?

Not exactly. I have a bunch of these ampoules, and I would like to produce enough Cs to fill one of them (~1 mL). If the produced amount reaches that, I would simply stop the distillation (unless I wanted to sell to members, which now that I think of it is probably a good idea in terms of not wasting Cs compounds).

Quote:
But anyway, I still strongly suggest glass tubing for the ampoule. If you look at various "large" Cs ampoules from the internet (the 99.99%) kind, they use cylindrical tubing with rounded bottoms not the thinner kind with flat bottoms.


True, but I'm not exactly hoping for a 'large' ampoule - unless those 1mL ones count as 'large'?

Quote:
Btw, do you have any sort of inert gas available? It REALLY helps.


Unfortunately, no. I might look into procuring some when the time comes, but as of now I have no argon/nitrogen/helium.

Dan Vizine - 25-4-2014 at 22:36

Well, that's the kind of ampoule you'll need a deft touch with. The glass is thin and it will sag and constrict in an instant if you use too hot a flame with a full -1 bar vacuum (or anything close) applied to it. When I seal those types of ampoules, a "vacuum" of 50 mm Hg is way more than enough. In fact, a small rubber pipette bulb pulls plenty of vacuum to give a good seal.

If you've never done it before, I'm sure you'll practice first. If you can, it is highly desirable to melt the seal into a well-fused somewhat rounded end w/o a sharp point.

On another front, your product quality will likely depend more on your reductant than on the CsCl, which is usually 99 - 99.9 % pure, metals basis. The typical Li sample may contain a per cent of Na or more. This will co-distill with the Cs.

Ca is easier to get as a pure metal, but to get a good yield you need small clean filings to achieve homogeneity in your charge as the reaction mixture is not very fluid at all. At least you don't need too much. Do this: Ca is available as chunks on eBay. Get some, clean it with a wire wheel or brush, clamp it in a cleaned-off vice and file it while catching the filings in whatever you have around. Do this right before before use. Not the day before, but immediately before.

You could use high purity Li to best effect though. This has become (easily) commercially available to the public in the last year.

These are not new facts but they are vitally important. If you pay attention to the little things you'll get Cs that is always solid at RT.





[Edited on 26-4-2014 by Dan Vizine]

Maya - 2-5-2014 at 15:57


Quote:

Well, that's the kind of ampoule you'll need a deft touch with. The glass is thin and it will sag and constrict in an instant if you use too hot a flame with a full -1 bar vacuum (or anything close) applied to it. When I seal those types of ampoules, a "vacuum" of 50 mm Hg is way more than enough. In fact, a small rubber pipette bulb pulls plenty of vacuum to give a good seal. If you've never done it before, I'm sure you'll practice first. If you can, it is highly desirable to melt the seal into a well-fused somewhat rounded end w/o a sharp point. On another front, your product quality will likely depend more on your reductant than on the CsCl, which is usually 99 - 99.9 % pure, metals basis. The typical Li sample may contain a per cent of Na or more. This will co-distill with the Cs. Ca is easier to get as a pure metal, but to get a good yield you need small clean filings to achieve homogeneity in your charge as the reaction mixture is not very fluid at all. At least you don't need too much. Do this: Ca is available as chunks on eBay. Get some, clean it with a wire wheel or brush, clamp it in a cleaned-off vice and file it while catching the filings in whatever you have around. Do this right before before use. Not the day before, but immediately before. You could use high purity Li to best effect though. This has become (easily) commercially available to the public in the last year. These are not new facts but they are vitally important. If you pay attention to the little things you'll get Cs that is always solid at RT.



Is there any particular way to get totally silver looking cesium without the yellow tinge?
Apparently even Alfa Aesear 99.98% has this yellow in it.... Yes, just a slight yellow haze. yes it is solid @ RT

I guess I could also make my own, less pure without the yellow?



Rubidium at this purity is quite silver looking

[Edited on 3-5-2014 by Maya]

BromicAcid - 2-5-2014 at 16:27

As far as I know, cesium <b>is</b> supposed to be gold in color.

Dan Vizine - 2-5-2014 at 16:50

Maya, That's a good question.

First of all, we need to define what they're talking when they say 99.9 or 9.999% purity. As I'm sure you know, there are two ways manufacturers advertize purities. One is an overall purity and the other is "Metals Basis". I've seen ampoules marked 99.999% purity that were golden, suggesting that's a metals basis value. The color likely comes from oxygen and that's not part of their assay.

On the other hand, my cesium is clearly less pure than that on a metals basis but for the the first few moments of its existence it is silver or close to it. It inevitably turns golden because of equipment limitations (meaning some oxygen leakage). I think it may be quite difficult to prepare it and preserve it as a silver metal. Even the various authorities who publish data on Cs don't have a consistent view. Some say it's silver, some say it's golden tinted. What I take away from that is that some samples had less O2 than others and that silver or close to it is likely the true color. I'd like to see what it looks like after a few distillations and before much time elapses.

I can tell you that I know for sure that the yellow color increases with O2 content. It actually goes through a pallet of deepening colors leading to black, the color of the highest oxide.

I guess my suggestion would be to try several redistillations in thoroughly baked glassware at the best vacuums you can attain with subsequent sealing under vacuum. I seem to have the recollection that you just may have access to high quality lab facilities? Even then, I don't think silver is automatically guaranteed.

[Edited on 3-5-2014 by Dan Vizine]

Maya - 3-5-2014 at 03:12

Those were my initial thoughts as well. Metals basis 99.98% initially with subsequent yellowing thru equipment imperfections. It is pretty tho' , even more impressive than Hg b/c of the phase changes.


Quote:

I guess my suggestion would be to try several redistillations in thoroughly baked glassware at the best vacuums you can attain with subsequent sealing under vacuum. I seem to have the recollection that you just may have access to high quality lab facilities? Even then, I don't think silver is automatically guaranteed.


you flatter me :D , yes I actually do have the equipment, but it would take alot to set up space wise and time wise right now. easier just to acquire it outright. maybe when I have more time I'll go for shiny by actually making a sample myself. That always gives you a nice warm fuzzy feeling!



Fleaker - 8-5-2014 at 14:23

The pure metal is silver and does not wet glass. Any oxygen and it will begin to shift more and more golden. In any event, it's its own getter so if it is distilled under a diffusion pump vacuum, your metal will be very clean.

There are some issues in determining purity of a Cs/Rb samples--if it is made into its hydroxide and handled in glass, it may leach out some Na/K. I suppose it may be better to carefully dissolve it in chilled t-butyl alcohol and then off to ICP with it.

Zyklon-A - 9-5-2014 at 09:27

Quote: Originally posted by Zan Divine  
You should strive for 0.001 mm Hg for the best results.

Can someone direct me to a suitable 0.001 torr vacuum?
I'm not sure what's wrong, but I haven't found anything even close:http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.T...

Burner - 9-5-2014 at 09:54

Quote: Originally posted by Zyklonb  
Quote: Originally posted by Zan Divine  
You should strive for 0.001 mm Hg for the best results.

Can someone direct me to a suitable 0.001 torr vacuum?
I'm not sure what's wrong, but I haven't found anything even close:http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.T...


Look at things such as the Welch DirecTorr (and similar) vacuum pumps (http://www.daigger.com/store/welch-directorr-vacuum-pumps209...). There are all capable of that level or performance.

Other possibilities would include multi-stage vacuum pumps such as the Welch DuoSeal (and similar) that can achieve 0.001 torr (http://www.chemglass.com/pages/pdf/manuals/AF-0350_WelchVacu...).

[Edited on 9-5-2014 by Burner]

HeYBrO - 10-5-2014 at 13:51

https://www.youtube.com/watch?v=W5B5mj6-fqk Zan! i think you should enter! great opportunity to get a free diffusion pump!

Dan Vizine - 10-5-2014 at 21:37

Thanks, HeBrO, but nothing that I do rises to a competitive level because none of it is new. This will deservedly go to someone working to extend something once considered to be a lab process into the realm of the home lab. My projects are somewhat less altruistic, they always have a commercial aspect designed to finance the next big project.

Zyklon-A - 14-12-2014 at 19:39

I'm looking for some sealant tape that can survive gaseous Cs.
I found something that looks promising, it's compatible at temps up to 635°C, is based on reducing agents, (and thus wont oxidize the Cs, maybe:o). It says it's made of "nuclear grade graphite and a nuclear quality petroleum-based carrier", whatever that means.
Here's the link:http://www.newmantools.com/chemicals/neo1260.htm, I'm looking at the first one in the list.
Does this look like it will work?
Alternatively I could weld all of the joints together, but I would like to have at least one (joint) so I could separate the heating chamber from the condenser if I want.
[EDIT] Also, I'll be using Ca to reduce the CsCl not Li, so the temperature will have to be a little higher.

[Edited on 15-12-2014 by Zyklon-A]

careysub - 15-12-2014 at 06:29

Quote: Originally posted by Zyklon-A  
...It says it's made of "nuclear grade graphite and a nuclear quality petroleum-based carrier", whatever that means.
...


It means "no boron" (down to the low single digit ppm level).

Zyklon-A - 15-12-2014 at 08:07

I see, thanks. Any idea if it'll work for the aplication though?

careysub - 15-12-2014 at 09:45

Quote: Originally posted by Zyklon-A  
I see, thanks. Any idea if it'll work for the aplication though?


According to this graphite is completely resistant to molten potassium:
http://ddenginc.com/products/gaskets/spiral-wound-gaskets/gr...

The petroleum carrier, I am less sure about. Alkali metals don't react with paraffinic hydrocarbons under ordinary conditions. But if you heat it enough to drive off the carrier, that won't be an issue in any case.

Zyklon-A - 21-12-2014 at 18:04

Thanks for the information, but I went ahead and welded all the joints. That sealant linked above cost $60 for the smallest quantity available, I can build an entire new apparatus for less than $20, so no thanks...

elementcollector1 - 15-9-2016 at 18:00

So I went and tracked down all the legal info on shipping caesium metal through FedEx, and here's what I found:

49 CFR 173.13 - Exceptions for Class 3, Divisions 4.1, 4.2, 4.3, 5.1, 6.1, and Classes 8 and 9 materials:

(2) For solids:

(i) The hazardous material must be placed in a tightly closed glass, plastic or metal inner packaging. The net quantity of material in any inner packaging may not exceed 2.85kg (6.25 pounds). For transportation by aircraft, the net quantity in one package may not exceed the quantity specified in columns (9A) or (9B), as appropriate.

(ii) The inner packaging must be placed in a hermetically sealed barrier bag which is impervious to the lading.

(iii) The barrier bag and its contents must be placed in a fiberboard box that is placed in a hermetically-sealed barrier bag which is impervious to the lading.

(iv) The intermediate packaging must be placed inside an outer packaging conforming to § 173.211.

(v) Not more than four intermediate packagings are permitted in an outer packaging.


§ 173.211 Non-bulk packagings for solid hazardous materials in Packing Group I:

(b) The following combination packagings are authorized:

Outer packagings:
Steel drum: 1A1 or 1A2
Aluminum drum: 1B1 or 1B2
Metal drum other than steel or aluminum: 1N1 or 1N2
Plywood drum: 1D
Fiber drum: 1G
Plastic drum: 1H1 or 1H2
Wooden barrel: 2C2
Steel jerrican: 3A1 or 3A2
Plastic jerrican: 3H1 or 3H2
Aluminum jerrican: 3B1 or 3B2
Steel box: 4A
Aluminum box: 4B
Natural wood box: 4C1 or 4C2
Plywood box: 4D
Reconstituted wood box: 4F
Fiberboard box: 4G
Solid plastic box: 4H2
Metal box other than steel or aluminum: 4N
Inner packagings:
Glass or earthenware receptacles
Plastic receptacles
Metal receptacles
Glass ampoules <- How is this an 'outer packaging'?

(c) Except for transportation by passenger aircraft, the following single packagings are authorized:

Steel drum: 1A1 or 1A2
Aluminum drum: 1B1 or 1B2
Metal drum other than steel or aluminum: 1N1 or 1N2
Plastic drum: 1H1 or 1H2
Fiber drum: 1G
Steel jerrican: 3A1 or 3A2
Plastic jerrican: 3H1 or 3H2
Aluminum jerrican: 3B1 or 3B2
Steel box with liner: 4A
Aluminum box with liner: 4B
Metal box other than steel or aluminum: 4N
Natural wood box, sift proof: 4C2
Plastic receptacle in steel, aluminum, plywood, fiber or plastic drum: 6HA1, 6HB1, 6HD1, 6HG1 or 6HH1
Glass, porcelain or stoneware in steel, aluminum, plywood or fiber drum: 6PA1, 6PB1, 6PD1 or 6PG1
Glass, porcelain or stoneware in steel, aluminum, wooden or fiberboard box: 6PA2, 6PB2, 6PC or 6PG2
Glass, porcelain or stoneware in expanded or solid plastic packaging: 6PH1 or 6PH2
Cylinders, as prescribed for any compressed gas, except for Specification 8 and 3HT





If I'm reading this right, the "correct" manner of transport would be to place a 1 mL ampoule inside a hermetically sealed bag, which is then placed inside a fiberboard box (is that another word for cardboard, or a different substance entirely?), which is then placed inside another hermetically sealed bag, which is then placed in another fiberboard box. Is this right? If so, that doesn't seem that bad. Though it does mention that the bags must be immune to the 'lading', which according to Google is the caesium itself. Not sure what plastics, if any, are immune to caesium - my Google-fu is ridiculously weak tonight.

Sources:
https://www.law.cornell.edu/cfr/text/49/173.13
https://www.law.cornell.edu/cfr/text/49/173.211


Fleaker - 23-9-2016 at 10:59

You can ship less than 1000 g of it. It is forbidden to go via air.

When I have had alkali metals like Cs and Rb shipped, they come in ampoules, bagged, put into a can w/ vermiculite, can sealed and put in a fiber box of the appropriate crush strength.

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