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RU_KLO
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Im trying to make NaNO2 for first time.
I choose NO2+NO bubbling in NaOH.
So I made a 4M NaOH solution (100 ml), in which a mix of NO2 - NO gas was bubbled.
NO2-NO gas was made from copper + 7M (aprox) HNO3 dripping (100ml). The dripping was adjusted, as so the inner color of the reaction flask. Mild -
almost transparent - red brown color was tried. (i.e. one drop every 1-2 seconds).
All this was in a negative pressure setup (a cheap 12V water/air pump was used).
It took a while - maybe 2 hours and copper needed to be replenished.
After this, ph was meassured, it was highly alkaline (NaOH excess).
(on a test, after adding some acid to a sample, till acidic, there were some red fumes from this solution. So probably some NaNO2 was in solution)
Next HNO3 was added to neutralize the NaOH. Ph was taken to 6-7.
Next a solution of Na2SO3 (unknown molarity) was added.
The idea was to transform the NaNO3 (from the neutralization) to NaNO2.
(some sulfur was in the Na2SO3 and some sulfur was precipitated - or I think it was
At the end was left with 250 ml which was boilled down till 50-40ml which crashed "a lot" of salt. (check picture)
Now, I need to somehow purify and get NaNO2.
Whats in the "soup":
1) 2 NaOH + NO2 + NO → 2 NaNO2 + H2O
2) NaOH + HNO3 = NaNO3 + H2O
3) Na2SO3 + NaNO3 = NaNO2 + Na2SO4 (maybe?) is this correct? (or maybe some sulfur is made?
what are my best route?
1) add more Na2SO3 to convert any NaNO3 left. (will an excess of Na2SO3 hurt?
regarding purification by recristallization, what the best route, because Im not having good results - maybe bad procedure.
NaNO2
Solubility in water
71.4 g/100 mL (0 °C)
84.8 g/100 mL (25 °C)
160 g/100 mL (100 °C)
Na2SO4
Solubility in water
Heptahydrate:
19.5 g/100 ml (0 °C)
44 g/100 ml (20 °C)
Na2SO3
Solubility in water
27.0 g/100 mL water (20 °C).
If I add little water, heat to dissolve everything, and let it crash out, will get the same result.
So how is it done?
a) add boiling water instead of cold till everything dissolves?
b) add cold water till everything is dissolves, remove X% of it (lets say 30%) take it to freezer or ice (0ºC) filter. then remove the last portion
till some cristals are seen?
c) filter what you got, dry, weight and from there, add enough ice cold water to dissolve the NaNO2 but not to the Na2SO4
Example: 10grs (dry mixed salt) was obtained,
(solubility per ml NaNO2 = 0.71gr (0ºC); Na2SO4 (0.195gr (0ºC))
So for NaNO2 is 14 ml of water. and for Na2SO4 is 51.28ml.
So if I add 14ml of H2O 0ºC, NaNO2 will be dissolved and excess of Na2SO4 will not.
Or maybe is simplier o more complicated than this (because of common ion effect)
Any help or step by step procedure for purifying is well received.
As side note, a small sample of this salt was tested with HCl and a lot of red fumes were watched.
and as bonus: If you have Sulfite and nitrate, you could directly made nitrite.... Is this correct?
thanks
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fx-991ex
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I dont think mixing Na2SO3 and NaNO3 in sln will reduce to SO4 and NO2. This usually is done in a crucible under high temp(300C) using CaSO3 instead
of the Na salt.(for ease of purification)
When you add acid it do make red fumes but that do not mean its NaNO2.
The Na2SO3 react with acid to liberate SO2 gas which probably react with NaNO3 to release NO2 while making Na2SO4.
I did something similar last year, mixing NaNO3 and CaSO3 gave red fumes upon addition of Acid. but after removing by filtration the CaSO3(No CaSO4 as
expected), it was only unreacted NaNO3, no red fume upon addition of acid.
What you want to do is, react your Na2SO3 With CaCl2, filter and keep he solid CaSO3. then react this CaSO3 with your NaNO3 under high
temperature(300C for 15 minute).
Then you can filter out the CaSO4 and evaporate water to keep the NaNO2.
Also the CaSO3 crystalize as hydrates so more is needed if its not dehydrated and having a slight excess dont hurt things. Most people seem to
overlook this part giving bad yield because they dont use enough CaSO3.
[Edited on 27-5-2024 by fx-991ex]
[Edited on 27-5-2024 by fx-991ex]
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RU_KLO
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After "bad" news from fx... and that is possible that I do not have any nitrite, performed the following test.
diferent reagents (used in the procedure) where added to a potassium permangante solution to see if they reduce it.
the nitrite? (prepared solution) and the sodium sulfite reduced it, the rest did not. (check picture)
So as fx said, probably I got no nitrite and the excess sulfite is doing the reduction.
So I will try to take a sample of the nitrite? and add some BaCl2 to precipitate BaSO3 (solubility 0.0011 g/100 mL) This will remove the sulfite and
left with nitrite "only" in the solution and check if this new solution reduce the KMnO4.
(note: already tried BaCl2 + Na2SO3 and a fine white precipitate precipitates)
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RU_KLO
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Last experiment was failure.
So i tried the Pb - Nitrate procedure. It seems it worked.
Tested the supernatant, few drops on potassium permanganate in H2SO4, it cleared, so there must be some nitrites.
Currently the Nitrite is drying. Im following Nurd rage permanganate standarization (with Sodium oxalate), so I can follow (previuos in this post)
titration of the nitrite/nitrate, so to know how good it was.
attached some pictures.
The sodium nitrite I got is white, not yellow as stated in this post from others.
The PbO I got is creamy white , but pictures show it is yellow...
Are this colors I got correct?
Lead was from UPS batteries, maybe some contaminats are there.
 
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Rainwater
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PbO is usually black, red, brown or yellow depending on the oxidation state.
That looks like white lead.... googling 2PbCO3·Pb(OH)2wiki
, heating a sample over a flame it should cause a color change, or react it with an acid to evolve CO2.
Heat it to about 650c and it should turn black if its PbO. Just remember its toxic and will contaminate all your gear
"You can't do that" - challenge accepted
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Master Triangle
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The aluminium reduction of potassium nitrate absolutely works to some extent, I dried a sample and the unpurified salt fumes strongly with HCl.
I used 20g KNO3 in 100ml water, with 4g of Al grinding dust, 6060 extrusion alloy, unwashed so it still had a tiny wax contamination and years old so
it is fully oxidised. Stirred and heated on a 55C hotplate. Added a knifetip of Cu2O as a supposed catalyst (no idea if this works in alkaline
conditions, or without chloride). A few drops of isopropyl were used to get floaters to be wetted. NO3- to Al ratio is just above stoichiometric if we
forget about all the reactions we don't want to happen.
Added ammonia and small amounts of NaOH (to dissolve oxide) with minor effect for several hours until it suddenly took off and started boiling from
the very exothermic reaction (this might be a bad idea with Al dust). Continued bubbling for about an hour. It didn't produce nasty amounts of
ammonia, so not sure how much of what came off was added by me and how much was from the reaction.
Ended up with a white precipitate with a few Al particles remaining, filtered that away and dried a sample which filled a vial with NO2 from a drop of
HCl. Just evaporating the rest down now, hopefully the aluminate is mostly precipitated before nitrite+nitrate begins coming out.
Anyone got ideas for removing aluminate, aluminium hydroxide and any excess potassium hydroxide? Not sure about this system, I added the remaining
dried sample back in for the evaporation and it seems there was a fair bit of Al(OH)3 since some would not re-dissolve on heating. The solubility of
nitrite in methanol might do it, and might even help separate some nitrate.
Also, the solution was totally clear and has only taken on the typical yellowish tint as I evaporate it. Is nitrite coloured at all? Or does it just
get the yellow tint from oxidation?
For repetition, there are a few things unclear that could be important: the potassium cation, whether Cu2O does anything, the alloy used. The speed of
the reaction could be important, but a rapid reaction certainly did not destroy all NO2- and probably formed most of it judging by the amount of Al at
that stage.
I'll do a permanganate titration at the end, pretty sure aluminate can't interfere?
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Master Triangle
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Yup, a pretty good success!
From 20g of starting nitrate I crystallised out 8g of unreacted nitrate and titrated what was left against permanganate, getting 5.78g or a yield of
~29%. If you go by just the nitrate that was reacted that would be a nearly 50% yield, or even higher if there was a significant amount that I did not
crystallise (likely).
I believe ammonia could interfere with the titration but that would have all boiled off during evaporation.
I think I'll try to do some optimisation runs, I could have certainly used more aluminium, and there are a lot of other variables to sort out too.
A lot to sort out with purification too; if you are all good with having some nitrate contamination it might be a good idea to add nitric acid to turn
all the KOH into KNO3 which is easy to crystallise out and won't attack your glassware, would probably help with precipitating out Al(OH)3 too. That
would have to be done after boiling off the ammonia to ensure you don't make ammonium nitrate.
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jackchem2001
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I have attempted reduction of KNO3 with CaSO3 a couple of times. I will leave some observations here:
You can't qualitatively monitor the reaction progress by taking samples at various points in time and adding sulfuric acid to them (the intent
being to look for the extent of nitrogen dioxide evolution from any nitrite present). However, the initial reaction mixture gives NO2 on addition of
sulfuric acid - clearly nitric acid generated in-situ is reduced by sulfite, so this method is no good.
The wiki claims heating sodium nitrite to decomposition (300°C - note a much lower temperature than the potassium salt) leaves behind sodium
hydroxide (?) and sodium oxide. In the case of the potassium salt, after leaving the reaction mixture in an open glass dish in an oven at 210-250°C
(using an IR themometer) for perhaps 4 hours, when water was added to the cooled reaction mixture some bubbling was seen. I expected this bubbling to
be from potassium oxide reacting with water to give hydrogen and potassium hydroxide, but the pH was only very slightly alkaline (i.e. the pH of my
tap water).
This suggests to me there may be no disadvantage to leaving the potassium reaction mixture at this temperature range for very long periods of time. If
reaction with atmospheric oxygen is feared, then an open container could be using during the initial heating period which could later be closed once
the system was up to temperature. I think a glass dish inside of a cast iron pot could be used to accomplish this.
My earlier run of this reaction failed - I suspect due to insufficient heating. I am yet to work up my current run.
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Sir_Gawain
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I’ve also had a failure with the KNO3 and CaSO3 reaction. I suspect it only works with sodium nitrate.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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fx-991ex
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I did it with NaNO3 only(i read somewhere that it could be dangerous with KNO3, am glad its not, i will give it a try next time).
You need to use alot of heat 300C very minimum, make sure both reactant are very fine and well mixed, slight excess of CaSO3 seem to help.
I think the reaction is very slighly exothermic if you can monitor the temperature closely, i did it in a porcelain crucible over a bunsen burner and
after the temp climbed a bit from 200something to over 300 i poked in it with a stainless steel wire and i could see a slight change of the matter,
its hard to explain but it didn't "feel" the same(probably just melted a bit from reaching close to 320C boiling/decomp temp). Or maybe thats just me.
Am thinking the CO2 from the bunsen burner probably help to displace some Oxygen to avoid re-oxidation(along with the excess SO3), but for bigger
batch the bunsen burner is not practical(hard to heat evenly) so better use an oven at 300-315 C.
[Edited on 11-7-2024 by fx-991ex]
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