How to Make Potassium Nitrate





Introduction: How to Make Potassium Nitrate

About: NurdRage is a dedicate group of science nerds trying to further amateur science with direct how-to instructions in video format. We saw what was already online and we thought "we could do better".....

Make Potassium Nitrate from Instant Cold Packs and Potassium Hydroxide

Warning: This reaction will produce large quantities of toxic ammonia gas. Perform the reaction outside or in a fume hood. Potassium hydroxide is highly corrosive; wear gloves when working with it.

Some instant cold packs contain ammonium nitrate as their active ingredient and when mixed with potassium hydroxide will produce potassium nitrate and ammonia gas.

Get an instant cold pack that clearly says it contains ammonium nitrate, cut it open, and pour the contents into a container. If its unused there will be a water pouch that you can discard. The rest of the pack is ammonium nitrate. Usually its coated in an anti-caking agent so it'll be off-color.

If you're using an already used instant cold pack then filter out the liquid and let it evaporate until it's dry. The crystals will be ammonium nitrate.

Take 80 grams of ammonium nitrate and dissolve in 70 milliliters of hot water. This will take some time so be patient. It will take even longer in cold water so use hot water when you can.

If it has an insoluble anti-caking agent then you need to filter it off through a coffee filter.

Separately, measure out 56 grams of potassium hydroxide. Potassium hydroxide is sold online to make homemade soaps and for biodiesel.

Add just enough water to completely dissolve the potassium hydroxide.

When both solutions are clear and ready, add the ammonium nitrate solution to the potassium hydroxide solution. This step will produce large amounts of ammonia gas and must be done outside or in a fumehood.

Leave the solution in a very well-ventilated area (outside is best) for all the water and ammonia to evaporate. You can also boil the solution to dryness, just remember it is still producing ammonia.

Now you have potassium nitrate!

To test it, mix a small portion with an equal amount of sugar and set it on fire. Normally pure sugar does not burn but if the potassium nitrate works then it will flare up in a purplish pink flame.

You can also make sodium nitrate by substituting the potassium hydroxide for 40grams of sodium hydroxide and follow the same procedure as the video.

In an upcoming video we will show how to make sodium nitrate from ice packs and baking soda. This requires a slightly different procedure than this video.

Please visit our YouTube channel at: for other videos like this one.



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    will lye work in place of Potassium hydroxide?

    So called "37-0-0" fertilizer is mostly Ammonium Nitrate.
    (In the spring say to the farm store clerk "I'm making a "Straw Bale Garden"." No further questions.)
    Potassium Chloride is found in some "Ice Melting Compounds" if you are in Canada or the Northren United States.
    Just disolve the Ammonium Nitrate in boiling water, one gallon can disolve as much as sixty-four pounds of Ammonium Nitrate, filter off the insolubles, then outside, slowly stir in the Walmart Potassium Hydroxide drain cleaner.
    The addition of the Potassium Hydroxide will cause the solution to heat up, maybe even boil, and give off copious ammounts of amonia gas, (DO NOT BREATH THE FUMES- POISON), so do it out behind the barn.
    As you stir, Potassium Nitrate crystals will form and sink to the bottom. The Potassium Nitrate can later be removed by filtering out the crystals and then washing out the water with denatured alcohol.
    Alow the alcohol to evaporate and store the crystals in an air tight container.

    kindly guide me that, how i can make potassium nitrate crystals form sodium nitrate and potassium chloride??

    extract from poo intense earth, like around barns, and if you live in cities there are place people pee all the time (in a lot behind a bush) or horse academies. I believe you can put the dirt back when you are done. Since you rinse the soil for nitrates then process further.

    look it up

    As a person with miltiple scars anddamaged eyes, (i was 11) I will tell you unless you are in a controlled lab you are foolish to do most chemistry shown here. And any time I can , I go to fireworks shows they are awesome. Enjoyable are the REDOX reactions that are exothermic. (did I get that right).


    ammonium nitrate is less reactive than potassium nitrate, making it less better for pyrotechnics, also it is hydroscopic: it attracts water. That means it cakes together and gets annoying. anyway, potassium is better to use.

    15 replies

    KNO3 is very hygroscopic

    Not nearly as hygroscopic as sodium nitrate or ammonium nitrate. In fact, for most environments, KNO3 is not hygroscopic. The relative humidity must be very high before it starts absorbing water.

    Thats weird, because my KNO3 if left outside turns into a puddle after 2 days, I live in Western Australia, the current humidity is 72% It may not be comparitively hygroscopic, but it still does trap enough water to become visually wet

    Why would you put it outside? I never put any of my chemicals outside.

    It was to demonstrate the hygroscopic nature of KNO3, all nitrates are soluble and most are hygroscopic and that was the first and only time I have ever left a chemical in the open

    Everything is hygroscopic under the right circumstances, even glass (I know it's weird but it happens) Are you saying potassium nitrate is more hygroscopic than ammonium nitrate?

    No, not everything is hygroscopic Take for instance wax, it is in fact hygrophobic and will not dissolve in water nor absorb it from the atmosphere And no, I never implied that KNO3 is more hygroscopic than NH4NO3, but as they are both nitrates they tend to be hygroscopic. The bottom line is; KNO3 IS hygroscopic, this ties back to my original arguement

    Take toluene, hexane, dichloromethane, diethyl ether, chloroform or any other substance that's hydrophobic and then add water, or even leave it on air long enough. Then remove all physical water you see until you get a clear solution of your organic solvent. Looks dry? If you take precise measurements you can find water, sometimes even a few percent, in the solvent. A great test is sodium benzophenone for the aliphatic solvents, or karl-fischer titration for the chlorinated solvents. In fact, it does take considerable effort to remove absolutely all water from a substance. Only substances which are reactive toward water (like thionyl chloride, or metals) will inherently never have water.

    I worked in an organometallic chemistry lab and water was a pervasive contaminant that we had to remove from just about everything. Even bottles of new solvent from our chemical supply company had trace amounts of water that would keep ruining our chemistry. It's common practice to dry solvents just before their use in certain types of chemical reactions, even if the solvent is new. How did the water get there? because the solvent absorbed the water from the environment, by definition that is what a hygroscopic substance is.

    If you think i'm lying google the topics of "NMR water peak", "Karl Fischer titration", "drying solvents" and "grignard reagents".

    And yes, you did imply that KNO3 is more hygroscopic by directly responding to the other poster's statement. Kinda like someone saying "Chocolate cake tastes bad, vanilla is better." Then you saying "vanilla tastes very bad". It strongly implies vanilla is worse than chocolate. Reverse the order of the statements and chocolate cake is implied to be worse.

    Granted, you might not have intended your statement to mean that, although it came out sounding like that. It happens, even politicians bung things up... repeatedly. Is that what happened here?

    BTW: "Hygrophobic" isn't a word, at least not in any standard dictionary i could find.

    By saying that every chemical apart from water reactive chemicals will absorb some water from the environment is a contradiction to you previous statement; "In fact, for most environments, KNO3 is not hygroscopic. The relative humidity must be very high before it starts absorbing water." I would like you to clarify whether or not KNO3 absorbs water from the environment because in this statement you exclaim that for most environments KNO3 is NOT hygroscopic, of course I am assuming that by most environments you would include your own. Yeah, I didn't intend to make it sound like KNO3 is more hygroscopic than NH4NO3, if you look at my first comment I simply said; "KNO3 is very hygroscopic" basically a statement in itself. Oh, and I meant to use; "Hydrophobic" rather than "hygrophobic"

    Alright then "KNO3 absorbs water from the environment when it's immersed in water" clear enough for ya? hehe, that was a joke, don't misinterpret it.

    The statement that everything is hygroscopic is supposed to be an agreement with you. At first i say KNO3 not hygroscopic. Then you say KNO3 is and give evidence. So, OK, I think about it and realized you're absolutely right so i agree with you and say everything else is too realizing that my interpretation of what "hygroscopic" is was wrong.

    Am i supposed to stick to a wrong opinion even though i realize it's wrong? Science doesn't work that way it changes and evolves with new evidence and theory. We'd never make any progress if I stubbornly defended something i realized wasn't true. Are you going to dig up my statement in pre-school where i said the moon was made of cheese? (mmm.. cheese....)

    Yeah, I didn't intend to make it sound like KNO3 is more hygroscopic than NH4NO3, if you look at my first comment I simply said; "KNO3 is very hygroscopic" basically a statement in itself.

    You made the statement of "KNO3 is very hygroscopic" as a direct response to another post. Therefore it cannot be interpreted as a "statement in itself", but in the context of the post it was made in response to. It is pretty clear in the comment log that it was made in direct response to another post by "pyrofirelighter".

    Otherwise this post in itself, although posted as a response to "Tombini" has no context and is merely the ramblings of a mentally deranged gardener to his computer (not to offend the mentally ill or gardeners ) . And therefore there should be no response or comment on it., because it's only a statement in itself. In fact, there should be no responses to anything I've posted, because they're all just statements without context. And i have never asked a specific poster respond to my any of them. All my questions were just to walls.

    I will have to break your wall with a Chuck Norris kick! lol I agree with most of what you have said although some of my comments didn't come out the way I would have liked, mostly being misinterpreted. Anyway the bottom line is; KNO3 is hygroscopic (insert big tick of approval) Just as long as you understand that my original point was to show pyrofirelighter that KNO3 is hygroscopic I will be contented (there have been many a time where my rockets have failed due to absorbing water.) By the way I love your comments on cheese and gardeners :)

    My next instructable will be on how to make chuck norris proof walls. :)

    That is impossible, its like dividing by zero or the square root of -1!

    the square root of one is i