15 replies to this topic

[neo]

hi!
I've seen this question at a Swedish pyro/he forum, but they don't seem to have a clue, so I thought it would be better to ask here..

is there some way to make potassium nitrate from NaNO3 and KCl?
the reaction is nice
NaNO3 + KCl = NaCl + KNO3
just that I don't know how I will make them react with each other..

don't care about the difficulties with separating them, I know it's very hard..
and don?t say that it is cheaper just to buy KNO3, because I know that to

[Stuart]

Just dissolve them both in boiling water, mix, and jobs done... almost. The result will be a mixture of Sodium, Potassium, Chlorine and Nitrate ions. You now want the Potassium and Nitrate ions to fall out of solution in the form of Potassium Nitrate. Just allowing it to cool would result in Potassium Nitrate precipitating, as its solubility at 0*C is tiny compared to that at 100*C. However, you would have some Sodium Chloride in there too, which we don't want.

Another method could be fractional crystallisation. You will need a Potassium Nitrate crystal for this. You would get one by allowing the solution to cool, and picking out the largest Potassium Nitrate Crystal, then boiling the solution again to re dissolve the precipitate. I believe Potassium Nitrate will produce long needle crystals when precipitating out slowly, so look for the largest one of them. Then, suspend the crystal in the solution, and the Potassium Nitrate will form on the suspended crystal.

There is a bit more too it than that, but thats the general idea behind it anyway. The link below makes for an interesting read...

http://www.waynesthi...om/crystals.htm

[fishy1]

to purify the kno3 you get after doing what stuart said, you could wash it several times with ice cold alcohol.

kno3 is virtually insoluble in alcohol, but the nacl, kcl, and nano3 are all partially soluble.

but if you just want it for bp, skip my step.

[neo]

thx!

finaly something makes sense.
so, its just mix same amount of moles of nano3 and kcl in boiling water, and let it crystallize?

1 mole of nano3 and 1 of kcl will give me 101g of kno3 and 58g nacl3. that?s pretty nice actually.
will test this later, will post the result!

now, to one other problem. (not really a problem but..)
I?ve only found a salt which is 66%kcl and 33%nacl.
is there anyway to separate those?
because that will give me 37g of extra nacl per mole of kcl..

one other thing, this fractional crystallization, will it only form kno3 crystals on a kno3 crystal? then would that be the best way to get it out.

[completebeginner]

Isn't kcl more soluble in water than nacl? if so you could just run cold water over it until the kcl dissolved and then recrystalize the solution and you would have a slightly more pure source of kcl

[EnigmaticBiker]

now, to one other problem. (not really a problem but..)
I?ve only found a salt which is 66%kcl and 33%nacl.
is there anyway to separate those?
because that will give me 37g of extra nacl per mole of kcl..

one other thing, this fractional crystallization, will it only form kno3 crystals on a kno3 crystal? then would that be the best way to get it out.

If needed in quantity, KCl can be produced easily with K2SO4 ("Sulphate of Potash") and CaCl2 (used as a drying agent, to reduce condensation).

Dissolve K2SO4 first, boil well and leave to cool, CaSO4 precipitates out. Filter through fine cloth, then coffee filter.

If there is any doubt over the purity of the ingredients, add a slight excess of K2SO4 rather than the (hygroscopic)CaCl2.
Any K2SO4 left in the KCl will crystallise out first.

[fishy1]

thx!



1 mole of nano3 and 1 of kcl will give me 101g of kno3 and 58g nacl3. that?s pretty nice actually.
will test this later, will post the result!

now, to one other problem. (not really a problem but..)
I?ve only found a salt which is 66%kcl and 33%nacl.
is there anyway to separate those?
because that will give me 37g of extra nacl per mole of kcl..

the impurity of 33% nacl will not affect the reaction. i've used it before and had great success making kclo3.

and btw, the yeilds won't be that great, they never are.

[alany]

Yes, but KClO3 isn't very soluable, while NaClO3 and KNO3 are extremely soluble, especially at high temperatures. The Calcium Sulfate method is the best if you must make KNO3, but it is so easy to purchase fairly pure I don' t know why you'd bother. KCl is also quite easy to get commercial ni large quantities, no questions asked.

[matthew]

hello.

today i bought potassium nitrate from an agriculture shop.it is good for use it in pyro compositions?

Thanks

[sizzle]

hello.

today i bought potassium nitrate from an agriculture shop.it is good for use it in pyro compositions?

Thanks

Garden grade Potassium Nitrate is fine for pyrotechnics use, this has already been discussed before if you search the forum.

[Anders Greenman]

This reaction yeilds a KNO3 of far better quality and with less work of purification.

K2CO3(aq) + Ca(NO3)2(aq) => 2 KNO3(aq) + CaCO3(s)

I've used it several times until I got my hand in 100kg pure KNO3 for a fair price (below 100?).
All the chemicals are readly aviable, but calcium nitrate have a unknown amount of crystal water, so it's difficult to find out the exact ratio between the two reacting chemicals.

[Mumbles]

It commonly forms a tetrahydrate. Probably the best way to do it, would be to dehydrate a small sample and figure out just how much water it has.

[Anders Greenman]

Maybe i'l try to heat up a small sample in a destillation setup. Should give good resaults.
Or just measure how much i need to get the reaction stop precipitating.

Edited by Anders Greenman, 01 August 2006 - 09:28 AM.

[alany]

Weigh it, dry it, then weigh it again.

[Mumbles]

Precipitating the carbonate, or even better yet oxalate, from a solution of the Ca(NO3)2 should give an almost quantitative measurement of the calcium percentage, which can be used to determine percent weight and such. I'd recomend sulfate, but it also forms a hydrate that is rather difficult to remove.