Just thought of a Possible HNO3 synth?

[xeluc]

I was sitting in Trig today and I remember reading that KNO3 will decompose into Nitrogen Oxides when heated. So if you had a container that you could heat KNO3 to decompostion with and have the resulting oxides bubbled into water, Couldn't you get HNO3 without distillation?

[woelen]

If you can get NO2, then you can make HNO3. But heating NaNO3 or KNO3 in order to make NO2 is VERY hard. You cannot accomplish that at home, the tempetatures needed for that are really high (IIRC over 1100 C). First, you get loss of O2, forming KNO2 or NaNO2, but this process also requires very high temperatures and cannot be done at home.

 

What is feasible, however, is to make NaNO2 or KNO2 from molten KNO3 and adding lead metal.

KNO3 + Pb --> KNO2 + Pb

 

Use excess KNO3 and add the metal to the molten KNO3. The reaction is smooth, not violent. Let the melt solidify. No need to purify it.

 

Add dilute HCl to the solid PbO/KNO3/KNO2 mix. You'll get loads of brown fumes (NO + NO2). These should be bubbled through water. You also need to assure that fresh air can enter the liquid, otherwise you loose a large part of your oxides (NO does not dissolve in water, but reacts with O2 from air to form NO2, which dissolves in water).

 

I don't think this is a really efficient route to HNO3, but it can be used to make crude dilute HNO3.

 

If you perform this synth, be very careful with the molten KNO3-mix and also be very careful with the insidiously toxic nitrogen oxides. These can kill you. Keep in mind, that NO2 has delayed effect. You can feel quite well immediately after breathing a lot of NO2, while 24 to 48 hours later you suffocate, due to buildup of water in your lungs (IIRC this is called lung oedemia (sp?)). Be warned, this is horrible and a friend of mine has experienced this to quite some extent after inhaling too much NO2! He felt really bad for more than one week, but fortunately he had no irreversible damage!!

[xeluc]

Well, I don't know wikipedia as well as other MSDS websites say KNO3 decomposes at 400 °C. Check it out. It's on the right down a little. I don't even have KNO3 anyhow. I do have Cu(NO3)2 however. msds says it decomposes at 114 C. This would work nicely, correct?

[woelen]

Cu(NO3)2.3H2O decomposes at a fairly low temperature. It gives NO2, O2, H2O and probably also some NO on decomposition. What remains behind is CuO.

 

The wikipedia page is correct. First, KNO3 decomposes at around 400 C to give KNO2 and O2. This reaction is very slow. Getting NOx from KNO3/KNO2, however, requires much higher temperatures, somewhere around 1100 C.

[xeluc]

So is that an affirmative on the Copper Nitrate then?

[woelen]

Yes, but it is not the best way to make HNO3. Don't you think it is a pity to use your copper nitrate for that? How much HNO3 and at what concentration do you want to make?

 

Making HNO3 of a concentration above let's say 40% will be hard. At higher concentration, the NO2 does not react any more with the water and NO and NO2 simply dissolve. The liquid will turn dirty green, due to a mix of red/brown dissolved NO2 and blue N2O3.

 

So, you'll end up with a liquid containing water, HNO3, NO2 and N2O3 (in equilibrium with NO+NO2).

 

If you want to make HNO3 at a larger scale, then I would go for distillation, simply at air pressure of a mix of KNO3 (or NaNO3) and conc. H2SO4, with a little water added. For details, YT can give better advice. For me, making HNO3 is not useful at all, I can simply buy 52% HNO3 for just a few bucks per liter, but I know it is different in many other countries.

[[w00t]]

Intresting - tho when i mix Kno3 with conc. H2SO4 i get white fumes and nothing else (the fumes smell like bleech i think) shouldnt i expect red fumes ?

[YT2095]

it will react a little without heating sure, but you`ll get best results when you heat it obviously, also you`ll not get any brown/orange fumes until the distilation is almost complete, then it starts breaking down and NOx gasses are produced. it`s essential that you use all glass aparatus, but at a push you CAN if you`re very carefull coat your flask cork/stopper with PTFE tape making sure there are NO exposed areas, and that will work as a temporary measure, you Must replace this after each use though.

[raivo]

Very small quantity (like 5ml) of HNO3 can be made with corck stopper without ptfe or other special protection. I have done this several times. Sometimes cork stopper lasts even more than one experiment.

[jdurg]

'']Intresting - tho when i mix Kno3 with conc. H2SO4 i get white fumes and nothing else (the fumes smell like bleech i think) shouldnt i expect red fumes ?

 

Well one thing is for certain, you are making a bunch of nitrogen oxides there because NOx's smell a LOT like bleach. Perhaps they are reacting with some other contaminant in the air, however?

[jowrose]

I know this post is somewhat going off on a tangent, but I figure this is the best place for it.

 

I am currently without sulfuric acid, because I cannot find it anywhere. Every store I'm in, I check all the drain cleaners and household products for something with h2so4, to no avail. So I figured I'd make it myself, albeit in small quantities.

 

I added some HCl to CuS04 (aq) and got a green solution (which I'm assuming is CuCl2 and H2SO4). I was trying to figure out a way to remove the CuCl2 from the solution. I think I could use a piece of lead, because lead chloride is insoluble, and then I could just filter out the acid, but I seem to have misplaced my lead supply (obtained from an airsoft gun...). Is there another way to do this? Could I just distill the solution?

[woelen]

Making H2SO4 at home is extremely difficult, if not impossible. Making it from HCl is not possible, because on heating, the HCl always is driven away. HCl is a gas and easily escapes the mix. The only possible way would be to take HCl and a soluble metal sulfate, which gives an insoluble metal chloride. There are only few metals, capable of this. The sulfate needs to be soluble, while the chloride is not. Ag(+) and Tl(+) have this property, but none of these you'll probably use for making H2SO4.

 

Otherwise, forget about making the H2SO4. You could have some luck at automobile stores and garages, where they sell battery acid. That is somewhere between 30% and 40% H2SO4, which is quite pure. You could concentrate that to 90+ %, but that is a very dangerous operation, which only should be carried out with the proper equipment (glassware) and fume hood (or outside).

[[w00t]]

and fume hood (or outside).

hmm im not sure tho but h2so4 doesnt smell. mine is relativly pure. higher than 90% - i been told it should..

[woelen]

It does not give smell or fumes when cold, but in order to obtain 90+% H2SO4 requires heating well over 200 C of the total mix. At that temp the liquid will be heavily fuming and these fumes are exceedingly dense and corrosive.

[akcapr]

Actually the fumes do smell but not as much as a halogen for instance.

[[w00t]]

It does not give smell or fumes when cold, but in order to obtain 90+% H2SO4 requires heating well over 200 C of the total mix. At that temp the liquid will be heavily fuming and these fumes are exceedingly dense and corrosive.

 

i had mine bubbling. couldnt actually smell it, even if i put my nose on to the fumes, the smell was very very little (wasnt irritating to eyes either).

[YT2095]

mine was very similar, in fact it isn`t so much of a smell, rather than a sensation, many many acids give this same "sensation" even citric when heated.

if you do get this "Smell" remove yourself right away, you`re doing damage!

[woelen]

That is the dangerous thing. Without you noticing it, you are destroying yourself by inhaling the fumes. Delayed effects can turn out exceedingly bad (edemia), so be careful! The more concentrated the acid gets, the hotter it gets and the more fumes are produced.

[YT2095]

I couldn`t agree more, hence the data presented in this thread gives SOME indication for prior warning of what it`s like when things go wrong.

as I said, if you can "smell" an acid, you`re at risk already.

Remove Yourself.

[[w00t]]

would melting kno3 and running electricity in to it form k + no3

thus creating nitric acid?

 

i assume the K would be rather dangerous

[xeluc]

Found this after a quick Google. Should help you out.

[woelen]

']would melting kno3 and running electricity in to it form k + no3

thus creating nitric acid?

 

i assume the K would be rather dangerous

You won't get K-metal at the cathode.

Any K-metal formed will react imemdiately with the molten KNO3 around the cathode. Around the cathode you can expect N2 gas to bubble out of the melt and K2O is formed, which remains in the melt.

Around the anode, you can expect NO/NO2/O2 to bubble out of the melt. NO3(-) is decomposed to NO2 and O2 and NO2 in turn will decompose to NO and O2 at the high temperatures involved, but I'm not sure to which extent this decomposition will occur.

[[w00t]]

Could, say 70% HNO3 be stored in anything other than Glass bottles?

i read somewhere that it can be stored in Telfon