August 24, 2019, 06:30:22 PM
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Topic: Drying out Cobalt nitrate or other hygroscopic chemicals  (Read 415 times)

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Offline global

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Drying out Cobalt nitrate or other hygroscopic chemicals
« on: August 03, 2019, 03:36:27 PM »
Cobalt nitrate - Co(NO3)2 ยท 6H2O - absorbs water (well, duh).  Is there any way to make it a more or less free flowing powder?
I have tried drying it out using heat (~130 F), but as most of you probably already know, all that did was change it form from a moist sticky "powder" to a liquid.  I haven't tried raising the temperature to 200 F yet, or applying vacuum, but figured someone here might know the best way to do it.

Offline wildfyr

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #1 on: August 03, 2019, 05:34:32 PM »
P2O5 in the system under vacuum. Are you familiar with the setup?

Offline global

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #2 on: August 03, 2019, 05:50:14 PM »
No.  Please explain, or provide a link.
Update: Did a search, didn't find much, but P2O5 is phosphoric acid, which I'm guessing will draw moisture from the Cobalt Nitrate.  What is the setup?  And how much vacuum?
BTW, can I use silica gel dessicant beads, or is phosphoric acid more efficient?
« Last Edit: August 03, 2019, 07:51:08 PM by global »

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Offline wildfyr

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Offline global

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #5 on: August 04, 2019, 07:27:10 PM »
Check out this post and image

https://www.chemicalforums.com/index.php?topic=99539.msg349490#msg349490

Awesome setup.  A picture says 1,000 words.  However, that sh!t is expensive, at least for me; $142 for 25 grams on ebay.  Is there another chemical that is cheaper?  Will silica gel work?  Do you know how many liters per minute your vacuum pump is pulling?

Offline Borek

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #6 on: August 05, 2019, 03:44:36 AM »
There are many drying agents, P2O5 is one of the ultimate ones and in most cases it is an overkill.

Simple drying at controlled temperature can be your best approach, try to get https://www.sciencedirect.com/science/article/abs/pii/S004060310500211X - it will tell you at what temperature to expect the anhydrous salt even without vacuum. Whether it will be sufficient to make the dry powder you need I have no idea.
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Offline global

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #7 on: August 05, 2019, 07:24:56 PM »
There are many drying agents, P2O5 is one of the ultimate ones and in most cases it is an overkill.

Simple drying at controlled temperature can be your best approach, try to get https://www.sciencedirect.com/science/article/abs/pii/S004060310500211X - it will tell you at what temperature to expect the anhydrous salt even without vacuum. Whether it will be sufficient to make the dry powder you need I have no idea.
Thanks, Borek.  I did a search for drying agents, there are quite a few, like Calcium chloride, magnesium sulfate, and sodium sulfate, as well as Potassium Hydroxide, which I already have.  It also occurred to me that Cobalt Nitrate is also a drying agent, and that controlled heat will dry it out.  I will try that first.  Thanks everyone, for all your help.

Offline wildfyr

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #8 on: August 05, 2019, 07:54:00 PM »
P2O5 is one of the ultimate ones and in most cases it is an overkill.

Working in an organic lab with easy access to P2O5 I freely admit I go right to it under vacuum every time. Why waste time with another method that could fail, when I know P2O5 will always succeed except in the most stubborn mineral hydrates? Such materials need the absolute christ cooked out of them (like, the sort of oven that needs a crucible for a container instead of glass) if that is the case anyways.

Offline Borek

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #9 on: August 06, 2019, 02:53:17 AM »
Why waste time with another method

Already answered earlier:

However, that sh!t is expensive

Plus, other drying agents are much safer.

Sure, when you have enough funds and your lab is well equipped it might be the simplest approach, but simplicity doesn't make it economically viable in general.
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Offline wildfyr

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #10 on: August 06, 2019, 09:12:27 AM »
I know access it not the same for everyone, but it sells on VWR for 2.5 kg for $90, which is very reasonable for almost any chemical. Anyone working in an academic or industrial lab should be able to get it at such a price.

Its about as safe as handling a concentrated acid. Its in the "don't spill it on yourself" realm.

I think it is the right choice for anything except very large scale industrial chemistry and home labs. Sure, if you aren't worried your compound will degrade, just cook it (possibly under vacuum), but if you are going to use an actual drying agent for active use (not storage), it deserves choice #1.

Offline Corribus

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #11 on: August 06, 2019, 11:00:05 AM »
Many hydrates can be dried by just baking at the right temperature; you can even track the process by weight. If possible, do it under nitrogen or vacuum. Different hydrates require different temperatures, and overbaking can lead to unwanted decomposition products. If you have a thermogravimetric analyzer you can track these processes yourself for new hydrates. Or use your friend google to see if someone else has already done it:

https://www.sciencedirect.com/science/article/pii/S004060310500211X
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline global

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Re: Drying out Cobalt nitrate or other hygroscopic chemicals
« Reply #12 on: August 06, 2019, 06:17:36 PM »
I know access it not the same for everyone, but it sells on VWR for 2.5 kg for $90, which is very reasonable for almost any chemical. Anyone working in an academic or industrial lab should be able to get it at such a price.

That's way better than the ebay price!  But I'll bet the shipping charge is horrendous...

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