Mg(NO3)2 ---> KNO3

[Davo]

I can find Magnesium nitrate at local stores here in Oz (sold as fertilizer), but KNO3 is really difficult to come across (I've only seen it at large agricultural depots sold in 50kg bags covered in oxidiser warnings) so i thought it probably wasn't a good idea to ask for it.

Would it be possible to convert the mag nitrate into potassium nitrate simply? I thought if I add KCl to a Mg(NO3)2 solution MgCl2 should form, along with aqueous KNO3. Is my thinking correct here, and how soluble is MgCl2?

[Bugger]

All those K and Mg chlorides and nitrates are highly soluble. They would not precipitate out, but the most soluble and the least soluble combination could be obtained by fractional crystallization, although it is time-consuming.

Bugger

[aikon]

...I've only seen it at large agricultural depots sold in 50kg bags covered in oxidiser warnings so i thought it probably wasn't a good idea to ask for it.

Ask for it! It's not forbidden to buy fertilzer, isn't it? Just have a self-confident manner and ask for it. I only see problems when you're 12 years old and try to carry the bag away with your bike. :)
And btw with 50kg of KNO3 you can to a lot of experiments for a long long time.

[Davo]

Might try getting some KNO3, after all, i have my own car and come from a semi-agricultural area. Its just that i'm i'm sure people are dead suspicious about any non-regular buying saltpetre and will need to be a good storyteller, esp with recent events. I've heard of people being asked for their name and address even for ASKING for it. Mg(NO3)2 on the other hand is relatively safer. I dont think its a very good oxidiser, although it may work for a few pyrotechnical compositions and possibly HNO3 manufacture.

Maybe the dudes at the agricultural depots wont be so concerned about KNO3 as NH4NO3 has overshadowed it alot lately. I think people were suspicious about KNO3 prior to 9/11 and bali because kewls used it to blow up letter boxes (or their fingers off) with. With the stupidity of most people around, they've probably forgotten about that and are more concerned with people buying AN. After all, AN is used in HE's whereas KNO3 is just used in pyrotechnic compositions and BP.

Can any Aussies tell me how they went about getting KNO3? P.S please dont say tree stump remover because nobody has even heard of it here.

[Hang-Man]

Mg(NO3)2 on the other hand is relatively safer. I dont think its a very good oxidiser hmmm, no. Magnesium nitrate is a strong oxidizer, it is in fact better than KNO3 (I've found it to be anyway). It will also burn your skin if you get it on your hands (on acount of it froming acidic solution with absorbed water??) Only downside is its hydroscopic as hell, how is it packaged at this farm store?

[meselfs]

I too think you should go for the 50 kg bag.

When I was 15 I purchased a 20 kg bag for around 16$ at a nearby feed store. Nobody asked any questions.

[Anthony]

I posted this yesterday, but it seems to have dissappeared.

Just say that your uncle (or whatever) asked you to pick him up a bag. Call it "nitrate of potash" if you like. If they ask for an address, then give them someone else's. If they ask for ID then say you don't have it with you. If they insist then say you'll waste no more time with their two-bit operation, and will take your business elsewhere. Then leave.

[hereno]

Couldn't you precip its hydroxide by the addition of KOH, Mg(OH)2 is nearly totally insoluble. Filter it, leaving you with a solution of KNO3. Then boil down to retrieve your potassium nitrate.

[megalomania]

Remember the FBI pamphlet for suspicious fertilizer purchases also suggests that the store clerk follow you out of the store and get your license plate number for later reporting to the government. Park around the corner and make sure nobody follows you out.

Read the pamphlet here: http://www.tfi.org/Publications/brochure%20pdf%20(final)%20-%20july%206%20-%20km.pdf

[ikbendirk]

forming acidic solution with absorbed water??

Don't worry, soluting Mg(NO3)2 leaves a nice neutral solution ;) (although NO3- is sliiiightly alkaline)

[Pb1]

Here's an idea: Add ammonia (either from decomposing (NH4)2SO4 or storebought) to your Mg(NO3)2, Mg(OH)2 will percipitate out, leaving you with a solution of NH4NO3. Boil this with KOH or K2CO3, giving you ammonia (which can be recycled:)) for the hydroxide or ammonia and carbon dioxide for the carbonate, leaving KNO3 behind.

[ProdigyChild]

I believe, your original idea (adding KCl) is fine. KNO3 has much lower sulubility at low temperature, so it will be the first to crystallize. Do make calculations before on how much to add and don't expect 100% yield.

[Jome skanish]

Adding ammonia to get NH4NO3 will probably not work. I tried with Ca(NO3)2 but failed completely, just 1/20 of the calculated ammount of Ca(OH)2 precipated, and thatmight even be carbonate-contaminations! It has something to do with to low electronegativity of the Ca and ammonia beeing too weak of a base to precipate the Ca(OH)2.

Try smaller ammount first as Mg(NO3)2 might not work either.

[FUTI]

adding ammonia in Mg(NO3)2 won't precipitate Mg(OH)2 since that one is solubile in aqueous ammonium ion solutions.

[cyclonite4]

Hey davo, could you please tell me the name of the store where you get the KNO3 from, I am from australia too and i have had no luck so far acquiring it.

btw, i agree about that stump remover thing, i havent found any "stump remover" around anywhere.

[senjoronie]

I imagine one could use potassium carbonate to precipitate magnesium carbonate, leaving K+ and NO3- in solution. If potassium carbonate is not available, sodium carbonate could substitute, although the result will be the more-hygroscopic sodium nitrate.

[Pb1]

solubile in aqueous ammonium ion solutions.

How does that work? It can't be from the ions themselves, since they mimic potassium ions. Is there some sort of complex involved? Is it due to the equilibrium between ammonia and ammonium hydroxide being shifted far to the left (the ammonia side)?

[FUTI]

Pb1 I believe you can find answer in any book of analytical chemistry. That fact is used in qualitative analysis which makes it very reliable from my point of view.

[NotTheMahdi]

I'm an Aussie too, a long time reader and a first time poster. If someone isn't selling you a component you need it may be because you look like an Arab. I'm sure you all have some hydrogen peroxide lying around if you need to bleech your hair in order to rectify this problem

[croc]

I brought my Ca(NO3)2 from a rural store. I asked him for KNO3 first but they didn’t have any left. When I got Ca(NO3)2 he asked what I was using it for and I told him I was changing it to KNO3 and making rockets with it.
Just like him I don’t think anyone would care as long as you don’t look like an Arab or tell them your making bombs.

BTW if you use Ca(NO3)2 and K2SO4 instead of Mg(NO3)2 you will get the insoluble CaSO4 which can just be filtered out.

[defiant]

The manufacture of KNO3 is described here:

http://docsouth.unc.edu/lecontesalt/leconte.html

Similar manufacture is described in US Army Technical Manual TM 31-210 (at Section 1 Part 2).

[cyclonite4]

I believe I read elsewhere that precipitated CaSO4 is gelatinous, and would be a pain in the ass to filter out.

I managed to get KNO3 quite a while ago, and got it delivered to my doorstep. All you need is a believable story, being freindly also helps.

[Alexires]

I live in Australia and I have gotten 25kg of KNO3 from a chem supply store, tech grade. Just ring up, and order it then go pick it up. Otherwise, if you feel like a long drive, come to SA and we'll load you up. Just give me some notice first ;).

Otherwise, I'd suggest the Ca(NO3)2, K2SO4 method then try vacuum filtration with alot of cold? water.

[cyclonite4]

Speaking of Ca(NO3)2, I noticed that a hydrangea fertilizer kit at bunning has two parts, one being a 250g pack of Ca(NO3)2. I can't remember if it was blue or red hydrangea, but I'm sure the box would state it. The kits are no doubt expensive (~$7), but it's an ok last resort, because it's likely that this is stocked at most bunnings or equivalent stores. Of course, little stops you opening the packet and taking out the Ca(NO3)2 bag and borrowing it, unless the store has cameras (I've found most bunnings dont).

EDIT: Vacuum filtration would probably make the job easier, however it would be inpractical on a mass scale, unless you improvised a larger apparatus. :)

[Omnius02]

http://www.roguesci.org/theforum/showthread.php?t=4247
I believe I read elsewhere that precipitated CaSO4 is gelatinous, and would be a pain in the ass to filter out.

Having tried the Ca(NO3)2 method I’ve found by just filtering the solution it catches the CaSO4 filtering quite quickly.
The only problem I’m having is dissolving my K2SO4 which I literally need 5-10 times the water for it to dissolve (even then its got bits left behind). It could just be impurities, but the percentage of impurities that must be contained is too massive.