Freeze Drying

[Justincase]

I don't like to ask.
But I got fed up with waiting for things to dry in my drying cupboard.
Well, a filtered enclosure where all my PC and Power amp's cooling fans are ducted through.
So I thought I would try Vacuum aided drying.
I have a Vacuum desiccator but vacuum pumps were KNF corrosion resistant, good for filtering not really high enough vacuum to help with drying.
So I picked up an Edwards Modulyo Freeze Dryer & Edwards Speedivac ED50 unit.
The ED50 is a good high vacuum pump that I can use with the Vacuum desiccator and Boekel Desiccator Dry Box.
but I am intrigued, The Edwards Modulyo Freeze Dryer unit has several layers of compressors and regulated systems.
but I can not find a manual.
Next, I will try and see if I can contact the manufacturers for advice.
But knowing what an assorted bunch of well-traveled gentlemen you are I thought I would ask if you might have some insight.
Many thanks and warm regards.
Justin

 

[etack]

I guess we need to know what you are drying?

i lot can be dried well with a heat lamp.

Eric

 

[Justincase]

I am using it for my compounds and silver cement.
Ammonium hexachloroplatinate.
But mostly for Silver nitrate at the moment.
I have a client that can take ten kilos a month.
I developed a staggered crystallization which has given me a good purity.
But it would be impractical to have that much product laid out on trays.
Not to mention after going through all the trouble of refining and then purifying through crystallization it would be a shame to contaminate by leaving it out in the open.
So I thought a vacuum system would speed things up and improve the process.

 

[g_axelsson]

Have you looked into rotavap and vacuum desiccators?

https://en.wikipedia.org/wiki/Rotary_evaporator
https://en.wikipedia.org/wiki/Desiccator

When it comes to drying metal powders I just put it in the oven and heat to slightly above boiling, but nitrates are sensitive to heating and breaks down easily. But you don't need to freeze the nitrates, so a normal vacuum desiccator should work just fine.

Göran

 

[Justincase]

I bought the vacuum pump for £195.
The rest I got for free.
Curious as to the difference between both systems.
I believe there is a good temperature fall when you introduce a vacuum in any case.
The dryer seems to mostly be an internal vacuum chamber which can be cooled to -100c if the gauge on the front is calibrated to the potential of the kit.
I am assuming that this large supercooled chamber would rapidly attract any moisture contained in a vessel which was connected much faster than a conventional vacuum desiccator.
I collect my cemented silver and compounds in the plastic pull apart Buchner funnels.
These make it nice and neat to dry slowly and brush out, but they do not react well to high heat.

 

[goldenchild]

If you have a fumehood you can dry silver nitrate from liquid to crystal form with controlled heat in a matter of hours. The temperature needs to be carefully controlled and kept under the deterioration point of silver nitrate. You can actually do it at any temperature under the deterioration point with the lower temperatures obviously taking longer. If your nitrate is already pretty much in crystal form and just needs the last bit of moisture (water/nitric) to dry out you can do the same thing as you would with liquid. The vessel should be glass and the more surface area the better. A glass tray is best. When already in crystal form the lower the heat the better. And the crystals should be agitated from time to time. Done properly you will have snow white crystals in the end.

 

[Justincase]

yes, I tried crash crystallization and heated drying.
But I have found a crystallization of a small percentage of the pregnant solution to yield very lovely large crystals of an exceptional purity.
It would be a shame to smash them into bits on a hot plate.

 

[Lou]

If you have a fumehood you can dry silver nitrate from liquid to crystal form with controlled heat in a matter of hours. The temperature needs to be carefully controlled and kept under the deterioration point of silver nitrate. You can actually do it at any temperature under the deterioration point with the lower temperatures obviously taking longer. If your nitrate is already pretty much in crystal form and just needs the last bit of moisture (water/nitric) to dry out you can do the same thing as you would with liquid. The vessel should be glass and the more surface area the better. A glass tray is best. When already in crystal form the lower the heat the better. And the crystals should be agitated from time to time. Done properly you will have snow white crystals in the end.

Actually silver nitrate can be melted and cast without deterioration. One of the methods for its purification in that other metal nitrates decompose to nitrites/oxides.

Silver nitrate manufacturing is done on a huge scale and it’s cheap as chips insofar as PMCs go. I’m absolutely shocked there’s any incentive to even do so on the ten kg/mo scale. But hey, if you’re able to make it work, good for you!

Also Justin...I HIGHLY advise against handing ammonium chloroplatinate dry unless you do so in a glove box. In industry we do not dry it but handle it damp up until it is ignited into sponge.

 

[Justincase]

Dear Lou
I only get 97% of spot for my finished fine silver from my metal trader, slightly over spot when I sell to silversmiths.
So I was looking for a reliable method to liquidate my surplus for a high a price as possible
I am working with my main jewelry client to develop a " Keum Boo" Alloy that is unavailable in the UK and should bring a premium.
And I asked my chemical supplier what the situation was on compounds such as silver nitrate. He agreed to take any I produced for use in his chlorine test kits, These are not for human consumption so have a lower threshold for testing and certification.
As to the viability of the project, Silver nitrate is a very easy synthesis, and the crystallization is fairly standard.
The only two hiccups I found were a slight trace contamination of chlorine in my distilled water necessitating a second distillation of H2O and finding suitable containers for the end product at a reasonable price.
I found silver refinement by its self to be unprofitable, but as I produce three grams of fine silver for every one gram of gold in any case I still have a regular stock to liquidate.Only a test run can provide a good answer to uncertainties.
I was aware of the hazards of platinum group salts, still stockpiling my cell black and harvesting Pd from my electrolyte. I have a tube furnace but no quarts liners as of yet. So it will be some time before I try and bring all those bits together.

 

[Lou]

Just be safe! Health is wealth!

 

[Justincase]

I will and do.
Thank you for your concern.
it is always appreciated.
J