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Arthur Dent
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Potassium Chloride and Potassium Nitrate
Yesterday, I bought some of the NO SALT brand salt substitute, knowing that it's mostly KCl, so I thought it would be a good start to synthetize
Potassium Nitrate.
But upon arriving home, I saw the detailed list of ingredients. NO SALT contains the following chemicals:
Potassium Chloride
Potassium Bitartrate
Adipic acid
mineral oil
Fumaric acid
Silicon Dioxide
Hmmm. that's a lot of crap I didn't take into account… 
So i figure that when adding Nitric acid (70%) and a bit of water to this mixture and heating it gently, the Potassium Chloride and Bitartrate will
react with the HNO<sub>3</sub>, the Adipic and Fumaric acid will (hopefully) decompose, leaving the insoluble silicon dioxide. No idea
what it will do to the "mineral oil" traces in the compound. But I guess I can get rid of the last two items by dissolving the salt in hot water and
let it decant before adding the Nitric acid...
After cooling down the saturated, reduced solution, i'll try to have the potassium nitrate crystallize by putting it in the freezer and separating and
then washing the crystals with some 99% isopropyl alcohol. I imagine that KNO<sub>3</sub> is poorly soluble in isopropanol?
Has anyone tried to turn NO SALT into Potassium Nitrate succesfully? What were your results?
Robert
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bob800
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NurdRage sucussefully used NoSalt to make KNO3: http://www.youtube.com/watch?v=xOjtlIxYYbs]. However, he calls the end-product "crude potassium nitrate", so I'm not sure of the purity.
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Arthur Dent
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Thanks for the tip. I watched Nurd's video and in it, he uses Ammonium Nitrate instead of Nitric acid. I didn't think about that!
but again, the other components might not be affected by the NH<sub>4</sub>NO<sub>3</sub> but probably will with the
full-power nitric acid... I realize as Nurd said that it would be much cheaper to get the real stuff straight, but that's not an option. And I just
need a small quantity.
Potassium Chloride, Potassium Bitartrate and Adipic acid are soluble in water, but the Fumaric acid, Silicon Dioxide and mineral oil aren't, so a wash
with water will get rid of some the impurities. I feel like there's a weekend experiment on the horizon for me... 
Robert
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not_important
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Once again, remember that KCl + HNO3 <-> KNO3 + HCl, and 3HCl + HNO3 is aqua regia which decomposes forming Cl2, NOCl, and NO among others.
Adipic acid will survive HNO3, it is/was produced by nitric acid oxidation of cyclohexanol or cyclohexanone.
Fumaric acid is slightly soluble in water, the amount in the salt substitute will likely all go into solution with the amount of water needed to
dissolve the KCl.
Might extract the salt substitute with acetone or isopropyl alcohol to remove the mineral oil and organic acids. After that use NaNO3 or NH4NO3 to do
a double displacement to get KNO3. Ideally use concentrations high enough to have NaCl ppt of the hot (near boiling) solution, filter to remove NaCL
and silica, then allow to cool to get KNO3 crystals. One recrystallisation serves to remove any chlorides in the KNO3. There's plenty of old books,
going back to the early 1800s, describing the process in detail.
Sometimes crude KCl can be found in garden supply stores as a potassium provider, it is also used to regenerate water softeners - sold in bags of 10s
or kilos. Both are likely much cheaper than salt substitute.
[Edited on 7-7-2011 by not_important]
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Arthur Dent
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@not_important: Thanks for the advice, this definitely an outdoors project with all these noxious gases emitted. As for the adipic acid, I guess that
recrystallization of the KNO<sub>3</sub> will be the point where i'll get rid of most of my impurities. I don't mind a bit of a loss in
yield to ensure fairly pure stuff. I might even do a second crystallization to purify it further.
Robert
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MrHomeScientist
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I also have a video where I made KNO3 with No Salt using the same method as NurdRage. I wasn't too concerned about impurities in the No Salt, since
they should be in very small amounts. I would think that crystallizing the product by cooling the solution should exclude many of the impurities, and
a second recrystallization would definitely give you high purity KNO3.
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blogfast25
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Initially that's where I got mine from but it contained some 25 % water insolubles (I think it may have been a mined product). Dissolving, filtering
and recrystallising gets you a fairly neat product (it has a decent difference in solubility between hot and cold water). But I got fed up with that:
now I buy it in (eBay mostly).
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mr.crow
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I have used No Salt before. Its full of all kinds of nasty stuff. Dissolve it in water then filter and you will be fine. Slimy gritty stuff is left
over.
To make KNO3 I prepare saturated solutions of NH4NO3 and KCl, filter the garbage out, mix together and boil down to the proper volume. You want all
the NH4Cl to stay dissolved at 0 degrees. About half the KNO3 will precipitate.
Double, double toil and trouble; Fire burn, and caldron bubble
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AndersHoveland
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KCl is also sold in huge bags as "water-softener" for home water use and for pools.
This should be pure enough: http://www.diamondcrystalsalt.com/Water-Softening/Products/P...
[Edited on 8-7-2011 by AndersHoveland]
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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Neil
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...check for KNO3 in hydroponics shops...
If you burn a sample of NoSalt the colour is pretty clean. I doubt any of the additives make it through the recrystallization in meaningful amounts.
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not_important
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Quote: Originally posted by Neil  |
If you burn a sample of NoSalt the colour is pretty clean. I doubt any of the additives make it through the recrystallization in meaningful amounts.
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However some NaCl drops out in the original crystallisation, a bit is retained in the first recrystallisation - often enough to give a yellow colour.
Depends on what you want the KNO3 for, "rocket candy" won't be bothered by that level of contamination.
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Neil
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Are you using LoSalt or NoSalt? The NoSalt I'm used to has no sodium streak in a blue flame.
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Arthur Dent
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@ Neil: I am using No-Salt brand. The first step of dissolving the salt and separating the insoluble gunk was easy. I used a 1l conical flask with a
stirbar and let the stuff whirl for an hour. After filtering, I had a litre of solution, which i will reduce by half before treating it with Nitric.
Robert
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Neil
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Good! simple is nice.
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Arthur Dent
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Getting back to this experiment, I finally got the time to take my KCl solution and boil it off to less than half, from 1 liter to about 350 ml. After
a bit of cooling, the stuff precipitated readily and then, I took the pasty crystals and dropped them in a glass baking dish and let sit at 120 C for
about 5 hours.
The resulting salt was very dry and with a bit of scraping and crushing, looked very much like table salt.
So I took about 80 g of dry KCl and mixed it with 100 ml of conc. nitric acid diluted with 40 ml of distilled water. Not much of a reaction, a bit of
bubbling and fizzing and it quickly subsided, leaving about 1/4 of the salt undissolved and the solution bright yellow. Of course, all of this was
done outside.
So I gently heated the solution and all the salt dissolved, and the solution is a deep golden yellow right now.
Should i keep heating the solution and drive off the remaining nitric acid or should I cooli it off and crystallize what I have?
I realize that this mixture right now is pretty much potassium nitrate dissolved in aqua regia... so I tread carefully with this setup (gloves and
goggles).
Robert
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plante1999
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You have made aqua regia (royal water)....
I never asked for this.
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blogfast25
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The yellow points to nitrosyl chloride.
Recovery of KNO3 from this might be tricky, unless conversion has been 100 %.
KNO3 has quite a steep solubility v. T curve, KCl is quite flat. That can be exploited but it's hard to do when you don't really know where you are.
Why did you dilute your conc. nitric acid?
[Edited on 12-8-2011 by blogfast25]
[Edited on 12-8-2011 by blogfast25]
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Arthur Dent
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@ blogfast25: I added some water because I remember reading that for many reactions, slightly diluted nitric acid seems to be more reactive than the
pure stuff, so I thought that slightly diluting the HNO<sub>3</sub> would make it dissolve the KCl a bit faster.
I boiled-off half of the solution, which is still straw yellow, but it has formed a thick salt crust. Since the stuff simmered at low for about 2
hours in an excess of nitric acid, there shouldn't be much KCl left, right?
I have gathered the crystals and dried them off a bit in a buschner funnel:
Edit: Here are the crystals, in the buschner funnel.
I took those crystals after a bit of drying off and dissolved them in water. The solution is crystal clear. I'll boil off most of the water and i'll
save the resulting salt. Is there a quick way to determine trace impurities of chloride in my nitrate?
Robert
[Edited on 12-8-2011 by Arthur Dent]
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MrHomeScientist
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| Quote: Originally posted by Arthur Dent |
I took those crystals after a bit of drying off and dissolved them in water. The solution is crystal clear. I'll boil off most of the water and i'll
save the resulting salt. Is there a quick way to determine trace impurities of chloride in my nitrate?
[Edited on 12-8-2011 by Arthur Dent] |
Adding silver nitrate is the standard test for the chloride ion, and it seems it would work particularly well in this case since everything else
should be nitrates.
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Arthur Dent
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@ MrHomeScientist: Silver nitrate! That's right! If there are any chlorides, a drop of that stuff should create a white insoluble AgCl precipitate!
Thanks for the reminder!
First i'll have to make some! A bit of silver at the bottom of a test tube along with a few drops of nitric should do the trick.
Robert
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blogfast25
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Hmm... silver nitrate is great as a very sensitive test for chloride but an expensive one to really remove all chloride.
I suggest a couple of well thought through recrystallisations, then test a small amount with AgNO3.
Good work so far! 
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MrHomeScientist
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Very true blogfast - if your goal is to remove the chloride rather than just test for it, buying a lot of silver might not be the best choice!
@Arthur Dent: Glad to help! It's definitely a very clear and sensitive test, and I use it often.
[Edited on 8-12-2011 by MrHomeScientist]
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Arthur Dent
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Yield: 50g of needle-like crystals (cooled slowly to room temp.)
I'll prepare some Silver Nitrate tomorrow to determine purity. For now, i'm happy to see these nice crystals.
Robert
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Arthur Dent
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Ugh. blogfast25, you were right.
A drop of AgNO<sub>3</sub> produced much cloudiness in a few of my resulting crystals dissolved in water. So there is indeed some KCl
contamination in my KNO<sub>3</sub>. I guess I didn't use enough nitric acid or I didn't let the solution boil long enough.
Robert
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blogfast25
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The situation is similar to any other HCl generator using H2SO4 for instance, to sqease out every drop of HCl concentrated acid is needed because HCl
is so readily soluble in water. That's why adding water was probably not a brilliant idea.
Not all is lost though: recrystallising should be able to get rid of most of the KCl (but you'll lose some KNO3). Try using the solubility data higher
up to calculate the right amounts of water to use. Of course some co-crystallisation may occur, so you might never be able to get rid of the last bits
of KCl... Allow the KNO3 master solution to crystallise quite slowly, that should help prevent any co-crystallisation...
Starting from a chloride, obtaining a completely Cl-free product was always going to be a hat trick and the AgCl test is very sensitive.
Look at it as an interesting exercise in chemistry: chemistry is a lot of things and 'the art/science of separating substances' is definitely one of
them!
[Edited on 14-8-2011 by blogfast25]
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