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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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jackchem2001
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Thanks for all of the comments
I hope not, as the decomposition temperature of potassium nitrite is much higher (>500°C) as compared to sodium nitrite (300°C), so would
hopefully give a better yield.
Quote: Originally posted by fx-991ex  | | 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.
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I think so too, as leaving potassium nitrate and calcium sulfite at 210-250°C for around 4 hours gave no detectable nitrite (adding sulfuric acid to
boiled down extracts gave only nitric acid and no NO2, and adding sulfuric acid to the material that did not dissolve in workup gave SO2 indicating
unreacted sulfite). At some point I will try using a loosely closed crucible (avoid oxygen) at much higher temperature and see if I get any nitrite. I
am not sure how to deal with the problem of heating the mixture evenly since I don't have an oven that can get any hotter than 250°C.
[Edited on 17-7-2024 by jackchem2001]
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Fantasma4500
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i thought i would add into the copper metal powder + sodium nitrate method..
CuCl2 is a bit annoying to make, CuSO4 is very readily available and at very cheap price, i was at one point in possession of about 250kg of it for
instance.
CuSO4 + NaCl = CuCl2 + Na2SO4
now seperating this is very tedious, so i never took advantage og this, its evidential that this reaction does occur in solution as the NaCl granules
when added to CuSO4 sol turns a vibrant green and more so when the next reaction occurs:
Al + CuCl2 = Al(SO4)2 + Cu
this Cu can then be reacted with NaNO3 at melting point temperatures to yield virtually 100% NaNO2
and to recap, the CuO formed can be reacted with NaOH+glucose for an hour to yield Cu2O which can work just as well as Cu powder, alternatively HCl is
reacted with CuO and Al is once again added- this method can also be used to produce hydrogen as a byproduct
NaNO3 + Cu = NaNO2 + CuO
i hope the general community will maybe in 2025 be able to grasp the simplicity and blessing that this method, as brought to us by woelen from an
ancient chemistry book is, a forgotten gem and a true blessing in current times where nitrites are scarce due to it offering an easy way out of life
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Master Triangle
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Turns out the copper is essential and probably catalytic in the aluminium reduction!
I just re-ran the aluminium reduction with twice the aluminium but no dash of cuprous oxide and the yield is only 15% of the original run. It did not
even seem to consume more of the nitrate despite using more aluminium.
I still have not tried the copper reduction despite having some copper powder around. I'll probably give a go eventually for comparison but I really
like the idea of using aluminium since it is so much cheaper.
I'll definitely have to try it again with more copper, probably as a Cu(II) salt since I doubt Cu2O is the ideal form for it. I feel like there must
be a connection to the Al/CuCl2 reductions that are done for organics like nitroalkenes, which is suspected of being an electrochemical reaction
arising from the partial copper plating of the aluminium surface, but could just be from the formation of urushibara copper or some heterogenous
Cu/Al(OH)x catalyst.
The fact this is strongly alkaline probably rules out some pathways like acidic dissolution of a copper oxide, so I suspect it would end up relying on
ammonia complexation of a copper hydroxide to return the oxidised copper to the aluminium for reduction, since you are not going to end up with a
copper chloride or such in a high enough concentration for the reaction rate observed.
I did some test tube reactions and aluminium in ammonia can rapidly reduce copper ammonia complex to the metal but only when enough KOH was added,
presumably enough to solubilise the Al(OH)3. I get a bright yellow colour on addition of the KOH too, a stark contrast against the blue ammonia
complex, any idea what this is? Only occurs where the KOH is concentrated.
So I guess I just have to find the ideal conditions for reducing copper with aluminium under alkaline conditions, but preferably without adding
near-stoichiometric hydroxide. Any ideas?
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Lionel Spanner
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As many posters in this thread are no doubt aware, highly soluble inorganic nitrites (and nitrates) are very difficult to recrystallise, being
extremely soluble in water and nearly insoluble in everything else. I recently found that a 30% aqueous solution of sodium acetate is an excellent
solvent for recrystallisation, with the caveat it doesn't work if there's a significant amount of another highly soluble salt present, e.g. sodium
hydroxide - in this instance, it has a nasty tendency to freeze solid at fridge temperature due to sodium acetate precipitating out.
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Keras
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Has anyone ever attempted the aqueous reduction of potassium nitrate by zinc?
I have, and it seems to work (I’m sure I obtained a yield > 50% – see the attached picture where the upper layer in the beaker is zinc oxide)
but it seems also to be heavily dependent on the quality of the zinc (I used scrap battery zinc that I activated by passing two minutes in 23% HCl),
which in my case seems to vary from batch to batch. The zinc/potassium nitrate mix, to which a tiny amount of copper sulphate can be added to further
activate the former, must be heated up to at least 70/80 °C for the reaction to take place, but there’s no need for higher heat or crucibles.
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Alkoholvergiftung
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Keras.
The reduction with ammonia solution would be better.
[Edited on 9-12-2024 by Alkoholvergiftung]
50g KNO3 in 150ml water. + 350ml ammonia solution desteny 0,96.
Addition under cooling 60g Zinc powder. Temperature must between 20- 25C after 45 minutes reaction is compled.
[Edited on 9-12-2024 by Alkoholvergiftung]
60g Potassiumnitrate the 50g are for Sodiumnitrate
[Edited on 10-12-2024 by Alkoholvergiftung]
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Keras
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Then I suppose you filter and boil the filtrate to get the nitrite?
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Alkoholvergiftung
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yes. But add slowly the zinc powder and the temperature must be hold between 20c and 25c. because if you do it fast the nitrate get reduced to KOH and
ammonia Gas and thats an fast reaction the mix boils over like an mentos in an Fanta. May be with higher chain alcohols you can fall out the nitrite.
[Edited on 10-12-2024 by Alkoholvergiftung]
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Keras
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Okay. I’ll first try to lay my hand on finer zinc, then I’ll try.
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Texium
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Thread Split
15-12-2024 at 09:43 |
Keras
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Apparently, trying to reduce nitrates using activated zinc powder (63 µm mesh) in acidic pH (drops of 23% HCl added from time to time) results in a
‘nascent hydrogen’ reduction which goes all the way to ammonium chloride.
Afterwards, adding sodium carbonate until the pH rises to about 8 results in an unmistakable release of ammonia gas.
There is no release of nitrogen oxides, so I suppose the reduction proceeds without formation of nitrous acid, which would decompose instantly at 80
°C. Besides, the pH never seems to go below 4.
Unfortunately trying to reduce nitrates to nitrites in a basic solution doesn’t seem to work at all.
[Edited on 17-12-2024 by Keras]
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Alkoholvergiftung
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have you used the mix as i wrote it? if the concentration of nitrate is to high it got reduced to nitrogen and than ammonia. if you use concentration
right it will be reduced to nitrit.(and temperature) For the Zinc ammonia mix.
Attachment: NitritDE000000168450A_2.pdf (65kB)
This file has been downloaded 18 times
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Alkoholvergiftung
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Part one. If you use translation software. They used an longer process first and old chemistry books state the same.
Attachment: NitritDE000000168450A_1 (1).pdf (78kB)
This file has been downloaded 16 times
[Edited on 17-12-2024 by Alkoholvergiftung]
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Keras
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Ich kann das einfach verstanden, vielen Dank 
No, I used my standard procedure: about 5 mmol of activated zinc covered in distilled water is mixed with 5 mmol of potassium nitrate dissolved in
about 10 mL of distilled water. The mix is stirred and brought to 80 °C+. This time, adding HCl dropwise slowly into the hot solution, waiting about
ten minutes then neutralising with sodium carbonate resulted in ammonia gas release.
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Alkoholvergiftung
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the Temperature is to high old process sayed never over 50C newer one sayed not over 25C. The Excess of ammonia is neccesary for the new one because
its an catalyst.Thats why the lower temperature. The older one is much more time consuming. If the titration is right and the old one is good done you
got near by the same yield of 94% old one and the newer one 99,3%
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Keras
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| Quote: Originally posted by Alkoholvergiftung | | the Temperature is to high old process sayed never over 50C newer one sayed not over 25C. The Excess of ammonia is neccesary for the new one because
it's an catalyst.Thats why the lower temperature. The older one is much more time consuming. If the titration is right and the old one is good done
you got near by the same yield of 94% old one and the newer one 99,3% |
Yeah, I saw that. Unfortunately I don’t have ammonia at hand, but I’ll try it as soon as I can. (Leider habe ich keine Ammoniak zur Verfügung
jetzt. :/ Aber ich werde das versuchen, sobald ich kann.)
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Keras
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Okay. So I bought a bottle of 13% NH₃ (d = 0.95) in a convenience store and tried the process with weights and volumes divided by 100. It definitely
works. However, I couldn't reach a ‘klar Flüssigkeit’. I had a lot of zinc oxide in suspension (see picture), and I stopped the reaction when it
seemed to me all the zinc had reacted. The few spots of zinc you see spattered in the white powder are zinc which had stuck to the stir bar.
The titration I did next was not very conclusive. I missed my first one, because I failed to take into account that the excess ammonia would
neutralise the few drops of sulphuric acid I had used with the permanganate. I then redid it with a large excess of acid. The yield was probably
around 65 to 70%, which is not bad, given that I really eyeballed it (~6.5 mL where 100% would have given me 4). Must have been mechanical loss in the
filtering and my process was very rough anyway.
It may be worth trying with 10x more reactants. Will do that if I have the time.
[EDIT: Ooops forgot to attach the picture! This is A 25 mL beaker btw]
[Edited on 19-12-2024 by Keras]
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Alkoholvergiftung
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I think this methode is better than the heating methodes, because you can make really big batches of nitrit  . Nitrites are insoluble in higher alcohols maybe an way to cristallize them out of solution.
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Keras
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Logically, zinc oxide is filtered off and excess ammonia can be boiled off. Why would you not simply boil the resulting solution to dryness to isolate
the nitrite salt?
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Alkoholvergiftung
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lot of energie consuming when you boil down an liter of water. Should there be unreacted nitrates you can extract tham with Ethanol water mix nitrites
are more soluble in alcohol than nitrates.
And i dont know when you heat them to long and the water is gone away do they slowly decompuse or retake the lost oxygen from air.
[Edited on 19-12-2024 by Alkoholvergiftung]
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