Make KNO3 from salt mix of 70% KCl & 30% NaCl

[navyou14]

Hello! I had an issue when I was planning to make KNO3 from salt substitue, unfortunatley where I live there is no Salt Substitute containing 99% KCl. I only found a salt with 70% KCl mixed with 30% NaCl! Is there still anyway where I can make KNO3 from the two salts or is there a way where I can separate the NaCl and the KCl from each other, so that I can make KNO3 with amost pure KCl?

[pavelcherepan]

From what I recall, NaCl and KCl form a solid solution that is K can freely substitute Na in the crystal structure and vice versa so what you have is not 70% KCl + 30% NaCl but in fact a solid solution with a formula (0.7 K,0.3 Na)Cl, unless it's a purely physical mixture of two salts. I think it would be a major hassle trying to separate those.

EDIT:
Speaking of major hassles one way you can get almost pure KCl is by diluting the compound you have in water and then 're-crystallysing. Both KCl and NaCl have similar solubility in water but there will be more KCl to begin with. Dilute large amount of your compound in warm water, noting how much you have put in there and what concentrations of both KCl and NaCl you have and then start cooling the water down. KCl will be the first to start crystallising. Calculate the temperature when NaCl solution will also become supercritical and stop cooling at this temp. Drain all the remaining liquid and what you'll be left with is almost pure KCl. Rinse and repeat until satisfied.

 

EDIT2 (this quote is a better description of the process):

 

 

This can be used in the process of recrystallisation to purify a chemical: it is dissolved to the point of saturation in hot solvent, then as the solvent cools and the solubility decreases, excess solute precipitates. Impurities, being present in much lower concentration, do not saturate the solvent and so remain dissolved in the liquid. If a change in conditions (e.g. cooling) means that the concentration is actually higher than the saturation point, the solution has become supersaturated.

Edited April 11, 2015 by pavelcherepan

[studiot]

What did you want potassium nitrate for and how much did you intend to make, may I ask?

[John Cuthber]

From what I recall, NaCl and KCl form a solid solution that is K can freely substitute Na in the crystal structure and vice versa so what you have is not 70% KCl + 30% NaCl but in fact a solid solution with a formula (0.7 K,0.3 Na)Cl, unless it's a purely physical mixture of two salts. I think it would be a major hassle trying to separate those.

 

 

 

I very much doubt it is a solid soluition. there's a phase diagram here for the related CaCl2 KCl NaCl H2O system and it doesn't include a mixed phase.

http://www.phasediagram.dk/quaternary/NaKCaCl.htm

 

 

this page

http://www.science.smith.edu/~jbrady/Papers/KCl-NaCl.pdf

suggests that you can make mixed crystals of the two salts, but only by melting the components together- adding water causes the phases to separate.

The two salts acn be separated quite easily by recrystallisation.

Edited April 11, 2015 by John Cuthber

[pavelcherepan]

I very much doubt it is a solid soluition. there's a phase diagram here for the related CaCl2 KCl NaCl H2O system and it doesn't include a mixed phase.

 

Indeed, there isn't one. I got confused.

[navyou14]

What did you want potassium nitrate for and how much did you intend to make, may I ask?

I am going to use it for a R-candy rocket

[Sensei]

If you have nitric acid and potassium bicarbonate you could try:

KHCO3+HNO3->CO2+H2O+KNO3

 

KHCO3 can be bought in shops with aquariums.

 

OTOH, in online aquarium shop I see also K2CO3, which would be even better.

Edited April 26, 2015 by Sensei

[navyou14]

If you have nitric acid and potassium bicarbonate you could try:

KHCO3+HNO3->CO2+H2O+KNO3

 

KHCO3 can be bought in shops with aquariums.

 

OTOH, in online aquarium shop I see also K2CO3, which would be even better.

Nice! But where can you buy Nitric Acid?

[navyou14]

However is there any organic compound where NaCl is super soluble while the KCl is totally insoluble and percipitates out??