Sciencemadness Discussion Board - Cheap nitrates to potassium nitrate

Cheap nitrates to potassium nitrate

Clonejeffie - 11-4-2017 at 13:08

Hello I want to make KNO3 with cheap nitrates such as Ca(NO3)2, NH4NO3 or NaNO3. I am thinking of just using calcium nitrate because I can get 25 pounds for 29.99 and I would like some help figuring out how to separate products from the reaction Ca(NO3)2+2KCl----->CaCl2+2KNO3

j_sum1 - 11-4-2017 at 21:37

I don't see any simple one-step route to do what you want here. The problem with what you have stated is that both CaCl2 and KNO3 are extremely soluble. Separation of one from the other by means of precipitation is going to be problematic.

Probably your most direct route would be to make HNO3 from your calcium nitrate and then react with K2CO3 or KOH to get the potassium nitrate. Not sure that would be worth your time or effort. It might simply be easier to source KNO3 some other way. Why specifically do you need potassium nitrate?

greenlight - 11-4-2017 at 21:40

If you want to use calcium nitrate I think it would be preferable to react it with potassium sulfate:

Ca(NO3)2 + K2SO4 - CaSO4 + 2KNO3

The calcium sulfate produced is much less soluble than calcium chloride so would be easier to seperate the potassium nitrate out.

Or if you want to use the ammonium nitrate there is this:

NH4NO3 + KCl ----> NH4Cl + KNO3

There is a full video of it here:

https://science.wonderhowto.com/how-to/make-potassium-nitrat...

[Edited on 12-4-2017 by greenlight]

Deathunter88 - 11-4-2017 at 21:50

Quote: Originally posted by j_sum1

I don't see any simple one-step route to do what you want here. The problem with what you have stated is that both CaCl2 and KNO3 are extremely soluble. Separation of one from the other by means of precipitation is going to be problematic.

I would argue that KNO3 is significantly less soluble than CaCl2, enough for precipitation to work. At 0C KNO3 is almost 5 times less soluble than CaCl2.

j_sum1 - 11-4-2017 at 22:02

Quote: Originally posted by Deathunter88

Quote: Originally posted by j_sum1

I would argue that KNO3 is significantly less soluble than CaCl2, enough for precipitation to work. At 0C KNO3 is almost 5 times less soluble than CaCl2.

OK. I was going from the top of my head. So maybe you are right. However, both are pretty soluble so there will be losses.
It is nice that KNO3 has a steep solubility curve which aids crystallisation of pure crystals.

Fulmen - 11-4-2017 at 22:26

No reason to guess:
https://en.wikipedia.org/wiki/Solubility_table

Below 20°C KNO3 is the least soluble salt, above that it's KCl. So it's possible but not really practical.

yobbo II - 12-4-2017 at 03:20

http://www.nakka-rocketry.net/knsyn1.html

google

Neme - 13-4-2017 at 03:14

Imho Ca(NO3)2 + K2CO3 would be the best bet.

Clonejeffie - 15-4-2017 at 08:57

Quote: Originally posted by Neme

Imho Ca(NO3)2 + K2CO3 would be the best bet.

I could not find K2NO3 so would KOH work?

Clonejeffie - 15-4-2017 at 09:21

Also it turns out the calcium nitrate I ordered is actually ammonium calcium nitrate so can I still use KOH or KCL?

Clonejeffie - 15-4-2017 at 09:23

Clonejeffie - 15-4-2017 at 10:06

Is there anyway of using this Ammonium calcium nitrate?

JJay - 15-4-2017 at 10:50

Elch Science did it here: https://www.youtube.com/watch?v=B8hzgXyxTQw

ave369 - 21-4-2017 at 07:39

Quote: Originally posted by Clonejeffie

Also it turns out the calcium nitrate I ordered is actually ammonium calcium nitrate so can I still use KOH or KCL?

Use a mixture of KOH and K2CO3. It will provide a one-shot removal of both offending ions. Calcium will precipitate with carbonate, and ammonium will be destroyed by OH- and a little boiling.

clearly_not_atara - 21-4-2017 at 09:25

Quote: Originally posted by Fulmen

No reason to guess:
https://en.wikipedia.org/wiki/Solubility_table

Below 20°C KNO3 is the least soluble salt, above that it's KCl. So it's possible but not really practical.

a mixture of cacl2 and water remains liquid much lower than 0C, which is missing from the table. Extrapolating the slope of the solubility curve tells me that you should be able to cool to -15 C and precipitate most of the KNO3.

However if you have K2CO3 it makes more sense to use this, collect limestone, and then evaporate to dryness.

Σldritch - 21-4-2017 at 14:07

Coincidentally i made calcium nitrate from ammonium calcium nitrate today by dissolving it in tap water, filtering it, and heating to drive of the water and ammonium nitrate. I ended up with a very white powder, not sure about the purity though.

Another method might be reacting it with cold ammonia solution to precipitate calcium hydroxide and then reacting the calcium hydroxide with more ammonim calcium nitrate to form ammonia gas and calcium nitrate. Point is it would only need a small amount of ammonia or calcium hydroxide to start it and you could get separation without much else.

Might not be very relevant because you could probely use ammonium calcium nitrate instead of calcium nitrate. Especially if you use potassium hydroxide to drive of the ammonia.

ninhydric1 - 21-4-2017 at 20:51

NurdRage did a video on reacting ammonium nitrate and potassium chloride then recrystallizing potassium nitrate at low temperatures:

https://www.youtube.com/watch?v=xOjtlIxYYbs

NileRed also did a video using calcium ammonium nitrate (which seems to be the one on hand) and potassium chloride:

https://www.youtube.com/watch?v=X8lGF41BYjA&t=2s

This relies on ammonium nitrate being a strong oxidizer. Not sure about the other nitrates though. Alternatively, you could look around your local hardware store for stump remover that contains potassium nitrate. Its usually relatively pure.