Sciencemadness Discussion Board

Potassium Nitrate Synth > plausable?

Punk - 5-3-2006 at 00:03

What are your thoughts on this hard to believe synthisis:

[Edited on 5-3-2006 by Punk]

evil_lurker - 5-3-2006 at 00:16

From my understanding, all you have to do is add potassium hydroxide to ammonium nitrate and you got your KNO3.

In the long run its usually cheaper to buy it from a chemical supply company, especially if your in the united states..

A good source you can get it from

Oh, and btw, most of the mods on here frown on not using search engines and doing real research.

The anarchist cookbook is even more frowned upon because it has somewhat dangerous directions and bad info. Even if the stuff in the cookbook work, those that are not "skilled in the art" could get seriously injured or killed.

mantis - 5-3-2006 at 01:36


add potassium hydroxide to ammonium nitrate and you got your KNO3.

instead of KOH you can also use K2CO3.

BromicAcid - 5-3-2006 at 01:46

This is the way nitrate was obtained back in the Civil War in America. Specifically cave dirt was employed. It think there may have been some other steps too. Additionally this procedure is outlined in some military manual somewhere, one of those improvised munitions manuals, I remmber reading about it when I was about 10 or so.

LiveWire - 9-3-2006 at 01:03

I always thought that you'd get a load of salt along with your potassium nitrate if you did that.

What is the chemical in the earth that gives potassium nitrate when mixed with potassium hydroxide?


MadHatter - 9-3-2006 at 03:01

LiveWire, there are any number of nitrates in the earth including naturally occuring KNO3
and NaNO3. NaNO3 is also called Chilean saltpetre. Nitrates are formed by the decomposition
of organic matter and by lightning.

During a thunderstorm, the energy produced by a bolt of lightning initiates a chemical
sequence as follows:

1) Nitrogen and oxygen combine creating nitric oxide(NO)
2) Nitric oxide and oxygen combine creating nitrogen dioxide(NO2)
3) Nitrogen dioxide and rain combine creating nitric acid(HNO3)
4) The nitric acid in the rain creates nitrates from compounds in the soil

Punk, if you can't order KNO3 and there is a garden supply shop close by you can make it
this way. The garden shops in my area, carry calcium nitrate and potassium sulphate in 4 LB
or larger bags. The metathesis reaction works as follows:

Ca(NO3).4H2O + K2SO4 --> 2KNO3 + CaSO4 + 4H20

The ratio of calcium nitrate to potassium sulphate is 1.355 : 1 or almost 7 : 5. The calcium
sulphate precipitates out of solution, being nearly insoluble. Use very hot water and filter
the CaSO4 out hot. Boil down the remaining solution until crystals just start to appear.
Put the solution in the refrigerator, or better yet the freezer. The KNO3 will crystallize into
white shards.

Evil_lurker, you're correct on the combination of KOH and NH4NO3. When mixed with a base,
the anion in an ammonium compound combines with the cation of the base forming a salt
and releasing ammonia. This is how ammonia generators work. In your reaction:

KOH + NH4NO3 --> KNO3 + H20 + NH3(gas)

[Edited on 2006/3/9 by MadHatter]

LiveWire - 9-3-2006 at 05:01

I see, so the potassium hydroxide turns all the other nitrates in the earth into potassium nitrate?

Isn't this a bad way to get potassium nitrate? Wouldn't you end up with a solution of potassium nitrate, excess potassium hydroxide, and other salts like sodium chloride?

[Edited on 9-3-2006 by LiveWire]

mantis - 9-3-2006 at 12:46


I see, so the potassium hydroxide turns all the other nitrates in the earth into potassium nitrate?

no, it depends on the ammonium-salts.


MadHatter - 9-3-2006 at 13:47

The key is fractional crystallization. KNO3 has a very wide range of solubility(in grams
per 100 ml H2O):

13.3 @ 0C to 247.0 @ 100C. The trick is to get all the other salts to remain in solution or
precipitated out before going after the KNO3. For example, calcium hydroxide would be
precipitated out when KOH mixes with any calcium nitrate in the soil. Ca(OH)2, or lime, is
barely soluble and can be filtered easily. Most hydroxides, with some exceptions are
barely soluble.

Adding more water and cooling the solution precipitates the KNO3 out. Just don't overdo it
with the KOH.

As for salt, NaCl, it wouldn't be part of the equation unless you used KCl instead of KOH.

LiveWire - 9-3-2006 at 23:52

I see, thanks for the explanations!

By the way, MadHatter, this is offtopic (sorry!), but you never replied to my U2U. Is it because you haven't had time, or because I'm just a newbie?


MadHatter - 10-3-2006 at 00:19

That's the biggest enemy I have, especially working 2 jobs.

Check your U2U for FTP access info. Sorry about the delay.