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Author: Subject: KCl or KHCO3 / K2CO3 from KNO3

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smile.gif posted on 24-1-2021 at 17:27
KCl or KHCO3 / K2CO3 from KNO3


This might sound strange as most information I can find is to make potassium nitrate from Potassium salts.....

Is there a way to KCl or KHCO3 / K2CO3 from fertilizer grade KNO3.

I Australia I can get a 25kg bag of KNO3 for $63. Works out around $2.50 per kg.

So far I am only able to get Potassium Chloride 1kg for $25 or Potassium Bicarbonate for $20 per Kg.

Thanks for any help you can give me!

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[*] posted on 24-1-2021 at 17:45

You might find some ideas here.
Potassium nitrate

Edit, this time with a working link

[Edited on 25-1-2021 by B(a)P]
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[*] posted on 24-1-2021 at 17:59

KCl is often available extremely cheaply as water softener salt. I'm not sure how common this is in Australia, but I found at least one site where it was available.

Boiling KNO3 solution with excess HCl should expel all the nitrate as NOCl. Repeated boiling will allow isolation of pure KCl. A similar approach is used in small scale precious metals refining to remove excess HNO3 that complicate precipitation of gold after dissolving in aqua regia.
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[*] posted on 24-1-2021 at 19:41

Quote: Originally posted by werdy666  

So far I am only able to get Potassium Chloride 1kg for $25 or Potassium Bicarbonate for $20 per Kg.

Have you ever looked for potassium chloride as a fertilizer? It is generally widely available, and I would be really curious if someone could get nitrate this way, but not chloride.

Just yesterday I went to the agricultural supply store to buy some medicine for our sick dog and I took the opportunity to get some KCl, it cost me only US$ 0.75 per 1kg. This salt, as it is presented in granules for use in agriculture, needs to be crushed and recrystallized (with an intermediate stage of filtering insoluble contaminants) so it can become useful in the laboratory, which certainly represents some work, but I can't imagine a cheaper potassium source.

25 AUD per 1kg of KCl seems to me a bit exorbitant, perhaps justified only if it is an analytical reagent.

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[*] posted on 25-1-2021 at 02:42

Maybe look for a source for food grade KCl? Where I live, I can buy snow white 99.9% pure KCl, EUR 15 for 2.5 kg, EUR 25 for 5 kg. More expensive than the fertilizer grade stuff, but it is very pure and can be used immediately. Still MUCH cheaper than your source, at 25 AUD for 1 kg.

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[*] posted on 25-1-2021 at 03:13

For me there are two sources for it: brewery which sells it for 10€/kg and fertilizer which sells it for 40€ for 25kg bag, but the latter may not deliver unless a full pallet is ordered or shipping may be huge.

Meanwhile, ordering a 25kg bag for 60€ including shipping from eBay from the other side of Europe is basically the cheapest for me currently. Just where in the devil I'd use 25kg of potassium chloride?

The issue is that K2CO3 has solubility of over 100g per 100mL while KCl has 27g and KNO3 13g. So attempting to crash this out will result only recovery of KNO3 with impurity of either.

Potassium method for getting pure nitrates for reagent use is very handy though, as it has very steep sol curve, allowing to extract any high solubility nitrate, for ex AN from very impure feed into very pure KNO3. Using less than eq amount of KCl will precipitate zero KCl along with the nitrate, leaving all other stuff in solution. KNO3 is non-hygroscopic allowing easy drying and is thermally and chemically much more stable than AN and will not release any parallel volatiles when heated or mixed(with strong acid).
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