Electrolysis of molten potassium nitrate?

[kmq]

Hey, everyone. I was reading up on electrolysis of molten NaCl, but I didn't really wanna try it cause I don't want to mess with the chlorine gas (by the way, would chlorine really accumulate to toxic levels if I performed the electrolysis outdoors over a long period of time?).

 

I figured that Potassium Nitrate, KNO3, should work if I wanted to create potassium intead of sodium, as I know that it has a reasonably low melting point (around 800 defrees F, I think), and I know that KNO3, dissolved in water, will become a K+ ion and a NO3- ion. Therefore, KNO3 should electrolyse into K and NO3, correct?

 

Before I tried anything I just wanted to inquire from some of the more experienced/smarter chemists around about whether or not NO3 is poison (through inhalation), or whether it will become poison in side reactions or reactions with the atmosphere. Furthermore, I have read that when heated, KNO3 will decompose into KNO2 and O2. Is it still possible to electrolyse KNO2, and will that release NO2 (poisonous) in a high enough concentration to become hazardous?

 

Of course I realize that this process would be inherently dangerous, from the high temperatures required and the production of potassium (which I know is highly reactive, don't get it wet, needs to be stored under kerosine, etc...). However, if I perform this experiment outdoors, over the course of several hours (wasting a whole lot of butane ) will any poisonous gasses build up in high enough concentrations to become dangerous (hopefully they will at least be less dangerous than chlorine)?

[jdurg]

What will happen if you try this in anything but an inert atmosphere is that as the potassium or sodium metal forms it will do so in a liquid state. With the fact that it's a liquid and there are highly oxidizing gases in the area at a high temperature, it will immediately catch fire and react. Chlorine gas will build up and immediately react with any and all metal that is formed at that temperature. (The heated chlorine may also ignite anything else in the area too). If heated high enough, any nitrate is likely to rapidly decompose flinging molten salt all over the place and causing numerous fires. Nitrates aren't the most stable of the 'stable' compounds.

 

If molten nitrates are electrolyzed, I'm pretty sure it will create oxygen gas and nitric oxide which is a VERY nasty gas. (I'd say it's even worse than chlorine). So yes, I would say that you'd get some nasty gas buildup and in the end you won't even have any potassium/sodium leftover because it will have reacted with the air and the gas you're also forming in the electrolysis.

[YT2095]

it`ll give off plenty of oxygen before you get it molten too, you`ll get molten potassium nitrITE, instead.

[jsatan]

I've not read all your post but you can use sodium hydroxide rather then sodium chloride, NaCl becomes Na(OH) anyway.

But it has to be done with no o2 around, You can melt Na(oh) (ina tin or something)

(Im not sure of the fumes so be warned) and stick some power through that, you will get a small amount at a time, but its fun to do.

[woelen]

If you electrolyse KNO3, then do not expect to get any K-metal. At the anode you will get NO2 and O2, but the formation of the NO2 is just the smallest of your problems.

 

At the cathode, if any K-metal is formed at all, you'll get an immediate redox-reaction between the nitrate ions and the K-metal. Remember, nitrate is a good oxidizer, used in pyrotechnics and it easily oxidizes weaker reductors, like sulphur, diverse metal powders, etc. So, imagine what happens if molten K is mixed with molten KNO3.

 

You'll also get some KNO2, due to decomposition of KNO3 in the molten state, but I expect that effect will not be too severe, just above the melting point of KNO3.