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Author: Subject: Cesium from CsCl
Zan Divine
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[*] posted on 12-2-2012 at 06:00


Quote: Originally posted by Fleaker  

Meant to get back with you, but I've been busier than hell.

Anyway, I'll put the RbCl in the mail.


Hi Fleaker,
I was wondering about the offer you made on 12-23-11 to send RbCl for reduction.
I asked you about it again on 1-22-12 and you said you'd send it.
That was 3 weeks ago and my customers keep asking about Rb. All I can say to them is that a guy on ScienceMadness said he was sending it...
Anyway, If you don't mean to send it, could you please just say so? If that is the case, I need to start looking elsewhere.
Thanks.

[Edited on 12-2-2012 by Zan Divine]
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[*] posted on 5-3-2012 at 14:08


First things first—

I want to publicly express my gratitude to Fleaker for his very generous gift of RbCl. Thanks to his thoughtfulness I will be reporting on the production of rubidium metal in coming weeks.

Yield as a function of mixing

After a half dozen runs with 4 different reactors, I’ve noticed a trend in % yields. Shorter, wider reaction mixtures are preferred over taller, thinner ones. Equally high yields can be obtained with either, but it’s much easier with the former. In all cases, the yields are far short of quantitative when the reaction appears to be over (it isn’t!).

This is what I believe occurs:

1) The heavy, unmelted CsCl settles to the bottom @ ~180 C when the Li melts.

2) They react during the settling process and at the resultant interface. Wider reactors have larger interfacial areas.

3) LiCl starts to build up. It’s heavier than lithium, lighter than CsCl, and probably not very miscible with either one.

4)The rate of Cs production drops off as the LiCl layer thickens and isolates the reactants..

Increasing the heat is counter-productive. Some Li may volatilize and the CsCl layer fuses.

To attain excellent yields, I run the reaction and collect distilled metal until the rate drops off appreciably. The reactor is cooled under vacuum, refilled with argon gas, opened up and the contents at the bottom of the reactor are mashed together with a screwdriver blade. The reaction is restarted and additional product is collected. This process can be repeated as necessary.

A method of physically mixing the reactants during the reaction would be a great improvement to this process.
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[*] posted on 6-3-2012 at 06:08


Excellent reporting there, Zan. Your explanations sound very plausible.

Any luck with the rubidium yet?

And to Fleaker: it's pure discrimination, this donating RbCl to one member and not all of us! ;)




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Zan Divine
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[*] posted on 6-3-2012 at 07:37


Hi blogfast25,

Thanks, I forgot to mention that the 2nd heating cycle gave as much product as the 1st. The 3rd, and last, cycle gave 25% as much product as cycle one. The point here is that these subsequent cycles are a major part of the yield, not just a small enhancement. When I first tried this out I wasn't expecting much.

Since this technique led to different fractions of the distillate being collected, some observations are possible. Fraction 1 wets glass totally & completely. Fractions 2 & 3 only wet it partially, somewhat similar to pictures I've seen of 99.5% material.

According to the FedEx tracking number which Fleaker so kindly provided, the RbCl is on the truck for delivery today.
I'm going to try to fit in a small scouting reaction within days, I hope.
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[*] posted on 6-3-2012 at 08:34


Quote: Originally posted by Zan Divine  
Since this technique led to different fractions of the distillate being collected, some observations are possible. Fraction 1 wets glass totally & completely. Fractions 2 & 3 only wet it partially, somewhat similar to pictures I've seen of 99.5% material.



You'll eventually have to have your metal analysed by XRF, you know! ;)




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[*] posted on 6-3-2012 at 15:24


I'd be glad to analyze it as I have ICP I can use and standards--just make it so that it's in solution already. Part of the delay is moving buildings. It's been a big drag. That and I had some serious health stuff come up that I never saw coming (at least I figured out why things were off in my life!).

Zan, I have probably 3 or 4 kilos of CsCl of my own for making Cs. Sooner or later once things have settled down for me, I'll probably do a kg batch of Cs. I have a pretty big diffusion pump here at work, so I can re-distill the Cs under high vac. If you want yours re-distilled when I re-distill mine, let me know.

I've never tried the lithium method. I do it with Ca flakes/granules and the yield is higher. I wonder if it's just an oxide issue--the Cs and molten Li are acting as getters for residual and trace O2/CO2. That explains why it's better at the end.




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Zan Divine
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[*] posted on 9-3-2012 at 17:57


Fleaker, I'm sorry to hear about your health issues. The diagnosis sucks but you can hopefully manage it well. The new generation of delivery devices is a lot more user-friendly at least.

I'm guessing that products formed from Li or Cs with H2O or O2 would be less volatile than the metal itself and not miscible with it once it cooled.

Also, I don't believe that we have much loss of Li or Cs due to H2O /O2 for these reasons:

1) An extra half molar equiv. of Li is present at the start and unreacted Li remains at the end of the reaction (vigorous H2 evolution in H2O, no fire)

2) For the last 60 g CsCl reaction, T.Y. of Cs is 47.4 g Cut 1 was 19.6 g, Cut 2 was 18.6 g and Cut 3 was 6.1 g for a total of 44.3 g or 93.5%

Still, there is no denying that some impurity is present and it is surprising that it appears to concentrate in the early fraction.

Just what would that be??

Cesium and rubidium are the most volatile members of groups I & II. Any of the others should be enriched in the latter fractions. I've only taken a cursory look so far, but I haven't run across any azeotropes mentioned for these metals and I didn't really expect to. Perhaps the most likely impurity in the distillate is rubidium (the 17 C higher bp notwithstanding)?

When crude Cs is redistilled (George Brauer's Handbook of Preparative Inorganic Chemistry Vol 1 p 962 ) it is the later fractions that are discarded, there isn't even a provision to remove a forerun if you wanted to.

It could just be that my assumption that my later cuts are purer because they wet glass less is wrong. But, the literature seems to suggest a positive correlation between purity and inability to wet glass.

All of this can be settled by analyses. To get the most mileage out of the least number of tests and to provide a little more insight into the relative merits of both Li & Ca I will go ahead and prepare Rb both ways and then compare yields and purities. The calcium has already been ordered.

Fleaker, I'll contact you when I have materials ready for analysis. Thanks for the offer.

[Edited on 10-3-2012 by Zan Divine]
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[*] posted on 12-3-2012 at 15:03


Hello "Zan Divine"

First, Congrats with your cesium production succes. Nicely done and look forward to see your future improvements.

I'm an element collector as well and for a long time I focused on group 1 element samples.
I've traded cesium for years and heres a few observations;

You talk about cesium price of 10 USD/g , 140 USD/g and so on depending on various things and then compare it to your price. The main thing about cesium is that as you know, cesium is not very expensive to produce. But to produce a sample of high purity in clean ampoules is very expensive.
So, 1 gram of your cesium cant compare to 1 gram of cesium is a clean ampoule.

I've had countless of cesium ampoules between my hands and of all of those I only have 3 ampoules where the cesium are more or less "perfect"
And by perfect I mean very high purity, no wetting of glass etc etc.

So, my experince is that Cs dont really have a "price per gram" , the price is based on quality of Cs and ampoule.

I've just returned from a "buisness trip" With a few 100g Cs and 250g Rb ampoules of very high quality. I will try to upload pictures of them on the forum soon. I will also soon update all my wikipedia pictures of Cs/Rb because I now have much better ways to photograph. (On wikipedia I'm "Dnn87")

Very much looking forward to your future projects. Would like to see you try Rb.
Good luck!

Dennis SK

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Zan Divine
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[*] posted on 12-3-2012 at 18:49


Hi Dennis,

Your observation that price depends on purity is quite generally true throughout all chemical industries & labs. That's why I've been careful not to compare apples to oranges and have priced accordingly.

However, to most element collectors there actually are generally accepted prices. The price per gram for Cs is quite simply the advertized price of the lowest priced provider that sells to the public and is easily found on the internet.

For most people in the US, that translates to GalliumSource. That means that the per gram price is $140 @ 99.5% and $165 @ 99.9% purity. I've noticed special orders on their website where Europeans have paid even higher prices. Your sources, of course, may vary.

The same goes for the $10/g price in bulk. For very pure Cs (99.99%), and at the 250 g size, cesium costs $2500 from GalliumSource.

The price of 99.8% pure caesium (metal basis) in 2009 was about US$10 per gram according to Polyak, Désirée E.. "Cesium" (PDF). U.S. Geological Survey. http://minerals.usgs.gov/minerals/pubs/commodity/cesium/mcs-...

The upcoming Rb synthesis, which will be done with Li and with Ca, is going to be analyzed. I'm very anxious to get this going, and by the end of this week I expect to do the Li reaction.

Eventually, I'm going to try to redistill a sample of my current Cs in an all-glass apparatus. Using a pressure-temperature nomograph, I estimate that with my pump I'll be able to stay within the operational range of borosilicate glass.

My biggest problem is too many projects at once. I'm also doing a lot of other custom work like the potassium shown below. This sample is 2.5 in long and 5/8 in OD.

front cropped.jpg - 54kB

[Edited on 13-3-2012 by Zan Divine]
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[*] posted on 12-3-2012 at 21:00


Hello.

I agree on your price examples. But Cesium is i tough market to put a price on. Personally I wouldnt compare cesium prices when looking at diffrent puritys/ampoules.
Theres just so much diffrence in Cs depending on the purity.
But yes, I guess the general public just look at the price and dont consider the diffence. But how would they know anyway?

Your potassium looks very good. Nice and clean.

I would like to try ampouling myself soon. But just too busy atm. It should be straight forward to ampoule some of the low melting point metals. Maybe even distill it into ampoules. (vacuum)

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13-3-2012 at 05:11
Zan Divine
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[*] posted on 13-3-2012 at 05:20


Hi Dennis,

Thanks for the comment on the K. I used a method described in "Handbook of Preparative Inorganic Chemistry Vol 1" by George Brauer.

As I couldn't lift the actual text, I've taken a couple screenshots and they are below. I modified the procedure a bit by glassblowing a spherical section in the melting area for larger capacity and by evacuating the tube before starting. It works amazingly well, and for those without the capability to apply inert gases or vacuum, it is unbeatable.

About Cs & collectors...another point about collectors is that for group 1 elements, they are used to having to settle for heavily contaminated samples. Usually no silver color whatsoever is seen. Most Na & K samples look like pieces of off-white marble. This is not to say this is what they want, it's just what's available. Everyone who has wound up with my Cs @ $50 (be it 99% or whatever) knew about GalliumSource but figured, I think, that saving 2/3 of the price and sacrificing 1% of purity was a good deal.

This is not to detract from your comments on Cs, which were good points, but the reality of most collections is that reasonable concessions save enough money to pay for the next sample or two.

We all seem to have the same common grouse...never enough time!













part1.jpg - 25kB part 2.jpg - 55kB



[Edited on 13-3-2012 by Zan Divine]
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[*] posted on 20-3-2012 at 11:16


So...Fleaker...you must think I'm an ass for rushing you on the RbCl and I haven't reduced it still!

It's the SOS....not enough time. I'm oblighed to go where my customers ask me to go and for a few weeks the main thrust has been on the ampoules of K and Na (published elsewhere on this site).

This week has been a blur of activity and Sat. morning the 24th, I'll be leaving for the ACS convention in San Diego (If any of you are there and want to say hi, we're booth 227). That will take most of the week and so my next opportunity to pick this work up will be in a few weeks.

So, sorry for the delay folks. Right now I'm the cat on the proverbial marble floor. Believe me, I'm anxious to start!
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[*] posted on 22-3-2012 at 10:36


It's ok! Life happens. I had the opportunity to play a little bit in the lab. Made a little sample set for a nice fellow who inquired. I imagine he'll put them in better bottles!

They're too small to use induction on, so I melted all of them with O2/H2, except of course the Ag. I plucked that out of one of the silver refining cells.
Might make some Pt, Pd, Ir, Ru, Rh Os, and Au gas phase grown crystals soon--I am prepping up for black phosphorus re-trial.


IMG_0972.JPG - 100kB




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[*] posted on 22-3-2012 at 11:33


Quote: Originally posted by Fleaker  
It's ok! Life happens. I had the opportunity to play a little bit in the lab. Made a little sample set for a nice fellow who inquired. I imagine he'll put them in better bottles!

They're too small to use induction on, so I melted all of them with O2/H2, except of course the Ag. I plucked that out of one of the silver refining cells.
Might make some Pt, Pd, Ir, Ru, Rh Os, and Au gas phase grown crystals soon--I am prepping up for black phosphorus re-trial.




If the black P works this time, sign me up for a sample.




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[*] posted on 22-3-2012 at 12:56


Quote: Originally posted by UnintentionalChaos  

If the black P works this time, sign me up for a sample.


Ditto that!
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[*] posted on 22-3-2012 at 17:12


So, where do I buy cesium? I want some too! :D



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[*] posted on 22-3-2012 at 21:40


Quote: Originally posted by Fleaker  
Might make some Pt, Pd, Ir, Ru, Rh Os, and Au gas phase grown crystals soon--I am prepping up for black phosphorus re-trial.

I would love to purchase samples of gas phase grown crystals!




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Zan Divine
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[*] posted on 30-3-2012 at 12:54


Dammit! Dammit! Dammit!

No sooner do I return from ACS than my company has me going to another trade show in San Francisco:mad:

(Did I ever think this was fun?!)

This kicks any further work down the road a couple weeks....:(
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[*] posted on 30-3-2012 at 13:22


I know the feeling. My school gives so much homework. I barely have time for any experiments. Break is coming up, so I might have some time...
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Zan Divine
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[*] posted on 30-3-2012 at 17:02


In many cases it isn't even the synthesis itself as much as it is the supporting work that consumes all the time.

On the surface, this thing takes a half day to perform. The reality, my reality anyway, is that it takes several days of support work including;

  1. Trips to the welding company to get argon, oxygen, & welding rods
  2. Trips to the hardware store for various parts
  3. Welding, grinding, cleaning & testing of the reaction vessel
  4. Orders placed for glass tubing, ampoules, glass syringes
  5. The clean-up operations. These aren't trivial. You've got to do a good job for several reasons.

All in all, this half-day reaction is really about a good number of days.
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[*] posted on 31-3-2012 at 05:40


Quote: Originally posted by Zan Divine  
In many cases it isn't even the synthesis itself as much as it is the supporting work that consumes all the time.

On the surface, this thing takes a half day to perform. The reality, my reality anyway, is that it takes several days of support work including;

  1. Trips to the welding company to get argon, oxygen, & welding rods
  2. Trips to the hardware store for various parts
  3. Welding, grinding, cleaning & testing of the reaction vessel
  4. Orders placed for glass tubing, ampoules, glass syringes
  5. The clean-up operations. These aren't trivial. You've got to do a good job for several reasons.

All in all, this half-day reaction is really about a good number of days.


Yeah, I imagine it's not a GRQ or a gold mine. Hard work for your bucks, more like... Don't give up the day time job just yet!

[Edited on 31-3-2012 by blogfast25]




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[*] posted on 31-3-2012 at 07:50


Ehh, you just need to make a lot of it, perhaps 2-3 kg per batch, then re-distill it all at once. Let the economies of scale prevail.



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[*] posted on 15-5-2012 at 23:27


How are you achieving a good vacuum seal between the metal joints? Was the elbow just threaded tightly onto the reactor (presumably with tapered threads?), or did you use some kind of metal gasket or high temp brazing afterward?

Were you able to measure the pressure during the reaction/distillation?
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[*] posted on 16-5-2012 at 06:37


The metal joints were (are) a concern. I wanted a joint compound of some sort and settled on a high-pressure, high-temperature formulation of molybdenum disilicide based lubricant/seal.

The actual pipe fittings were very problematic (to me anyway). They are Chinese in origin (nothing but the best at Home Depot, eh?) and are not the best ferrous products around by a long shot. They tend to give welds and brazes very prone to porosity. I can't tell you how many weld/grind/test cycles I went through to get acceptable vessels.

I did not have the ability to measure the vacuum during earlier work, but I just acquired a McLeod gauge. My upcoming rubidium synthesis will be the first where I'll have pressure data.
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[*] posted on 21-5-2012 at 19:47


anything new on the cesium sales? XD



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