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Polverone
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I buy my NaNO2. This was just to see if there was an easier way than the traditional reduction of molten nitrate with lead to prepare it on a lab
scale. It's useful for preparing hydroxylamine, azides via hydrazine and alkyl nitrites, and diazo compounds. It can also be used to perform a
few organic oxidations or to prepare small quantities of pure nitrogen.
PGP Key and corresponding e-mail address
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JohnWW
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Sodium nitrite is also widely used as a food preservative, mostly in meat small-goods like sausages, bacon, and "corned" and smoked and
canned meats. However, some studies have shown that excessive consumption can be carcinogenic, possibly through its formation of nitrosylamines when
metabolized in the presence of amino-acids.
John W.
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BromicAcid
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There was actually an entire chapter on that very effect in my college toxicology class. But it is determined that the amount used is a
'safe' dose only contributing a few hundred (possibly thousand) cases of cancer world wide a year.
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chloric1
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Other method
I would not know percentage of yeilds but...Potassium Nitrate and granulated sugar in approx 6:4 ratio. This is a potent pyro mix and leaves molten
nitrite behind! I know because Conc. HCl gave lot of NO2 with traces of Chlorine from HCl oxidation. be very careful becuase the smallest spark sets
this mix off and it burn vigorously at WHITE HEAT Also ignition of KMnO4 with
sulfur produces the green form of MnS!
Fellow molecular manipulator
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frogfot
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I recently got some strange results with Pb/KNO3 procedure..
Melted 207 g 99,95% lead (bought from a metal supplier) in an iron crucible, and while stirring mechanically I added 101 g KNO3 in small portions
(5-10 min). This was then continiously stirred mechanically, mix foamed a little. Foaming increased a bit after about 12 min and reaction mix started
to glow from beneath. After a while whole mix started to glow red and it started to give of thin white fumes! The bottom of crucible was red hot on
outside.. Here I ceased heating.
It cooled after about 1 min. Though while stuff was still dark red glowing, about half of the mix have separated as solids, while rest was liquid.
I'd guess that solids was sodium oxides because of high mp and because extraction liquid was very basic. I'm currently extracting it..
So, is this glowing normal? I'd guess that this was a runaway reaction, but how could one prevent it using only a gas burner..? Maby it ignited
because of friction between stirrer and crucible..
In earlier test I used same ammount of carbattery lead (~6% antimony). After ~40 min reacting (with same setup) this gave 17% conversion with regard
to recovered lead.
EDIT: Oki, I've got about 55g KNO2, most likely not pure.. Maby that "runaway" wasn't that bad, though there are probably lots of
KOH in the product..
[Edited on 21-9-2004 by frogfot]
[Edited on 22-9-2004 by frogfot]
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Theoretic
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The solids were probably a mix of KPbO2 and K2PbO3, they hydrolysed to give KOH.
I suggest that nitrate is reduced in molten state by Na2SO3. I don't see any probable side reactions, to separate the product from Na2SO4 let it
cool, I think they'll form two separate layers. To fully use the reducing capacity of NaHSO3, convert it to Na2SO3 with Na2CO3, then SO2
won't be lost during conversion to CaSO3, and CaSO3 will all precipitate, you'll also get twice as much. Reduction with Na2S in a molten
state should also work.
A combined reduction with sulfur should be interesting. Sulfur powder can be melted down and solidified to form a gob (to prevent runaway and
over-reduction), then put into molten nitrate. It should be reduced like so: 2NaNO3 + S => 2NaNO2 + SO2. SO2 should be led into Na2CO3 solution
(not, NaOH, for reasons of greater availability and lesser alkalinity, which could otherwise induce suckback). Na2SO3 thus formed could be reused for
reduction.
To prevent splashing during carbon reduction, first metl down nitrate and then throw in C powder, bit by bit.
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crushpack
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making KNO2
Here's my contribution to problem of KNO2(potassium nitrite) making. Here in Czech rep nobody can buy this substance legally and the classic way
for its preparation (heating of melted mixture of lead and potassium nitrate) is at least somewhat complicated and no ever successfull.
so what's this method I use: the yield is practically kvantitative and it's simple and fun. I can't remember no disadvantage of that.
You must have some lead tartrate by hand before you start, if not then let it precipitate from the solution of sodium potassium tartrate(cream
of Tartar) to which you pour the soln of lead nitrate- nothing can't be simpler.
Once you have this "organic" lead add it to the melted Potassium nitrate, but only in small portions, since the reaction that occur is
really violent. the mixture of KNO3 and lead tartrate is pyrotechnic in fact.
When you've done this you've done all if you don't consider purification of KNO2 from PbO2 a problem. (If you do, then extract it by
hot water and crystallize).
For those interested in reaction mechanism here is my own explanation(which means that it can be wrong):
when you heat lead tartrate you'll get a pure lead but in so a very fine form that its pyrophoric, which means that it will burn in air (when
aerosolized) or with some oxidizer as f.e. KNO3:
Pb + KNO3 = PbO + KNO2
So it seems that only differrence between this method and the classic one is only in the form of lead. this method takes an advantage that the larger
the surface of the reactants is the bigger is the yield.
Its simplificated but I can't give here more detailed explanation,for I must go now. So I'll give here only the total reaction scheme (it
can be wrong I repeat and for some other suggestions i'll be thankfull)
PbH2C4O6 + 4KNO3 = PbO + 4KNO2 + 4CO2 + H2O
Edit by Chemoleo: Çrushpack, there was an existing thread on nitrites as you can see. Although your
contribution is appreciated, a quick search does help too 
[Edited on 29-10-2004 by chemoleo]
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crushpack
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Apologize: the formula for potassium tartrate is PbH4C4O6, I've missed two hydrogens attached directly to carbons...So the equation of reaction
should be corrected:
PbH4C4O6 + 5KNO3 = PbO + 5KNO2 + 4CO2 + 2H2O
Anyway, since I really can't be sure that the reaction run exactly according to this equation maybe that was not so a big mistake. But the truth
is that the KNO2 really originate by this (when I dropped a little of diluted H2SO4 on isolated product, voluminous red foul smelling fumes of NO2
appeared). I've also in my hurry forgot to post something about advantages of this method (compared to classic reduction of PN with lead):
1/the reaction does not need stirring
2/lead tartrate regeneration from PbO byproduct is possible. Just transfer PbO to Pb(II) salt by some acid (acetic is preferable) and then to
precipitate lead tartrate by some soluble tartrate salt (Cream of Tartar f.e.)...let's imagine how would you try to get pure Pb from PbO instead)
3/ Normally you need to bubble CO2 through the aqueous soln of prepared KNO2 to get rid of some soluble lead salts by precipitation. I suppose that
the CO2 originated by this "improved" method should be sufficient to solve this problem completely.
Well, one disadvantage is here as well:
when you put lead tartrate into the molten KNO3, you must do it carefully in reasonable small batches. When the "organic" lead is added to
molten PN at once or when mixed with it before and then heated, it has almost the same effect as black powder under same conditions.
I'd be thankfull if someone would find out the real yield of KNO2, since I have now lack of time for experimentation. 
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JohnWW
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"Apologize: the formula for potassium tartrate is PbH4C4O6"? You will need to give another apology: that is the formula of lead(II)
tartrate, not potassium tartrate.
John W.
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crushpack
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thank you, it was only misprint from me, I wanted to give the formula for lead tartrate of course
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skippy
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potassium nitrite - qualitative success
I've given the fabled KNO3 + Pb -> KNO2 + PbO a couple of tries and have a report to make.
Basically it comes down to stirring, from what I've seen. I tried three attempts and each time I stirred more than the last and each time had
better results. On my third attempt I bent a fork and lashed it to a dowel so I could better mix the pot. The prongs were bent so they would both
scrape the bottom of the pot and comb through the lead and nitrate. This seemed to really help. The lead gets broken up during the stirring into
little dark grey lead flecks that react alot better than a big pool of lead.
The melt was reacted for 1 1/2 hours, with constant stirring, and then allowed to cool. The salt was dissolved in warm water and a cake of tan orange
lead oxide intersperced with lead flecks was left. A small fused pool of lead was underneath this cake. The amount of lead left suggests that well
over 50% of the nitrate was converted. The salt extracted also reacted vigorously with HCl, producing copious deadly brown fumes. 
Question:
Anybody have a good idea on how to test how pure the nitrite is?
Thoughts:
Stir, stir, stir!
When/if I get time to do this again, I think I'll try a mechanical stirrer, as it is not much fun stirring this stuff for so long!
Edit by chemoleo: The title is NitrIte, not NitrAte. Merged thread with existing thread.
[Edited on 16-1-2005 by chemoleo]
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PainKilla
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Why bother with that reaction... Im pretty sure that KNO3 decomposes to KNO2 via heating.
2KNO3 ---(heat)--->2KNO2 + O2
Or am I mistaken?
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frogfot
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Skippy, what kind of lead did you use?
With car battery lead, reaction seems to go very slow like you've described.
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S.C. Wack
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Many find the simple heating of nitrates unsatisfactory. I made some this way, but then I found a better method - burning some cash instead of some
nitrate. The loss of O is slow below 650C, but the loss of N (Nasty oxides) is fast above 850C. One ends up with an equilibrium mixture of nitrate and
nitrite up to 800 or so, where oxide formation becomes a factor.
This is because the nitrite, despite the usual temp of dec given, loses O quite slowly to a point, but gains O from the air at a higher temp in a
narrow range. There isn't a whole lot of room between this range and the loss of N temp. 780 looks favorable, though I've never seen a ref
explicitly say so or give exact yield.
Experimenters may find it best to use a scale and watch out for darkening.
Mellor's N supplement gives refs for alternatives to Pb, etc - but they are all in German.
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skippy
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The lead was from some old lead piping I had kicking around. I don't know how it compares with battery lead.
I guess the whole deal is a bit of a hassle if all you want is the nitrite, but I wanted some PbO too, so getting both seemed pretty cool.
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frogfot
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About nitrite content analysis...
Do anyone know if reaction:
NH4Cl + NaNO2 --> NaCl + 2H2O + N2
goes to completeon? Maby some very kind person can even test this with pure nitrite (rolleyes).
If reaction is compleate, this would be a very simple method to determine the content of nitrite. One would only collect evolved nitrogen in an upside
down measuring cylinder (filled with water) and then substracting moisture content. This could give very precise results.
In inorganic book they use following procedure:
Saturated NH4Cl solution is heated nearly to boiling and a saturated solution of NaNO2 is added dropwise.
Since I recently got a mechanical scale (+/-0,01g) I'm quite eager to analyse my nitrite from the runaway Pb/KNO3 reaction I mentioned above..
[Edited on 18-1-2005 by frogfot]
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S.C. Wack
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Vogels Inorganic Analysis says that of trace of nitrate is formed. How much a trace is, they don't say.
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frogfot
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Alrighty, I've just conducted abovementioned nitrite determination experiment.. Set up a twonecked flask with reflux condencer and a
rubberstopper (with syringe). The gas outlet was connected to a washing bottle with dilute H2SO4 and then to a reversed measuring cylinder. Washer
with acid was to remove formed ammonia (my nitrite is very basic).
I refluxed NH4Cl soln, and when pressure stabilised, I added a water soln of 1,00 g of my impure KNO2 (from runaway exp) with a syringe, dropwise.
This gave 215 ml gas, I calculated content of KNO2 to 0,705 g (taking into account added volume of nitrite, the temperature of gas and partial
pressure of water).
This means my KNO2 is of about 71% purity.. Quite simple test, though I'm not sure about it's accuracy.
Btw, "trace" of nitrate wouldn't hurt
[Edited on 22-1-2005 by frogfot]
[Edited on 22-1-2005 by frogfot]
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CycloKnight
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Sodium or potasium nitrite
Is there a reliable process for converting the nitrate into the nitrite using heat?
I recall using heat to decompose KNO3 into oxygen and nitrite. Does anyone have any experience doing this on a scale larger than test tube
proportions?
I did use the search engine, and I couldn't find the info I'm looking for.
I read that sodium nitrate can explode if heated beyond a certain temperature. Is that only if contaminants are present or is that a genuine risk once
takes by heating sodium nitrate to decomposition?
I assume the latter to be the case.
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Polverone
Now celebrating 21 years of madness
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Sodium nitrate alone will not explode from the application of heat. People here have had some success making nitrites on a somewhat-larger-than-test
tube scale by making fuel-poor pyrotechnic mixtures of nitrates with sugar or charcoal and igniting them. Muspratt suggests heating a fuel-deficient
mixture of KNO3 and lampblack to produce crude KNO2. The classic method of stirring molten nitrate with molten lead has also been used on a modest
scale, though it is tedious. I have tried heating calcium sulfite with NaNO3 in just sufficient quantity to reduce it to NaNO2, as per a patent, and
it seemed to work though I did not scale up beyond test-tube quantities.
A zinc-copper couple in nitrate solution or amphoteric metals in alkaline nitrate solution are supposed to reduce nitrate to nitrite. Unfortunately,
they will keep on reducing to produce ammonia. I don't know if the process can be controlled to give reasonable yields of nitrite if the
quantities are calculated and vigorous stirring is used.
I found a one-line reference in an old book saying that zinc dust would reduce a neutral aqueous solution of KNO3 to KNO2, but I never saw any
reaction myself. Perhaps my zinc was too pure, or there were unnamed necessary conditions (like the reaction taking place in an autoclave at 150 C).
I know that heating aqueous ammonium nitrate solution with lead dust will produce some lead nitrite, though that's not exactly what you're
after.
Simply heating NaNO3 or KNO3 strongly can give a fair amount of nitrite. It's good enough to make alkyl nitrites without further purification,
but it wouldn't be suitable for all purposes. I see no reason why it shouldn't work on larger scales, but you need a suitably durable vessel
and an intense heat source. Finely divided manganese dioxide is supposed to accelerate the thermal decomposition of nitrates.
PGP Key and corresponding e-mail address
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CycloKnight
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Nitrite
That is very informative, thanks Polverone. That is indeed the information I'm looking for. In the near future, I will be conducting some
experiments so I can establish a working, reliable and replicable procedure for the conversion of sodium nitrate to nitrite. At that time, I will post
the results on this thread.
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skippy
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runaway lead + nitrate
I've found that Frogfot's above mentioned runaway reaction is actually a good thing. Without the runaway, the reaction procedes too slowly.
The runaway can be started consistantly by strong heating while beating the molten mix of nitrate and lead with an old whisk. (protective clothing!).
The stirring seems to whip the lead into fine granules which can be burned quickly if the nitrate is sufficiently hot. The 2l stainless steel pail I
was using turned a bright cherry red from the exothermic heat. It was a pretty cool sight, a glowing 1000 deg C pot of seething molten goo!
Here's some good stuff from the hive archive (http://www.synthetikal.com/hiveboard/index.html)
http://12.162.180.114:90/synthetika/hiveboard/acquisition/000458114.html
After removing the small dome from the inner file-clay mantle of a Rossler gas-furnace, place upon the mantle a strong iron-wire triangle, and set
upon the triangle a shallow iron dish (2.5cm high, 12cm upper diameter) having a smooth bottom. Place 85 grams of Sodium Nitrate (NaNO3) in the dish
and close the furnace. As soon as the dish has become faintly incandescent and the molten nitrate just begins to give off bubbles of oxygen,
gradually add 206 grams of lead in the form of old pieces of sheet lead or lead tubing. The lead is at once vigorously oxidized, and, if sturred
continually with an iron spatula, becomes almost completely converted into oxide of lead in half an hour. Empty the contents of the small iron dish
into a large deep iron one, and repeat the operation several times, using the same amounts of Sodium Nitrate and lead. Place the various products in
the large iron dish, extract once with boiling water, and decant upon a creased filter. Dry the reside of lead oxide and set aside for the experiment
on page 52. Pass a strong current of CO2 into the still boiling-hot filtrate,for a few minutes only, filter off the lead carbonate which separates,
and neutralize the solution while stirring it, by carefully adding nitric acid from a pipette or burette. Evaporate the solution to crystallization.
The crystals which separate first, consist partly of nitrate and may be used again for remelting with lead; the mother-liquor gives pure nitrite. A
normal solution of the nitrite is prepared by dissolving 69g of it in water and diluting to one liter.
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frogfot
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Great!! Skippy, I bow to you.
This means I have a reliable supply of nitrite for this summer (and further). One only needs to come up which nitrate is better to use.. sodium or
potassium..
Seems like syntheses with both NaNO3 and KNO3 has a possibility of purification. That is, excess of the first can be precipitated from aqueous
solution by alohol and the second can be removed by cooling out. So, using KNO3 seems to be cheaper..
I only have KNO3 on hand, and NaNO3 has to be made (from Ca(NO3)2 and Na2CO3).
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garage chemist
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I had some sucess with the preparation of NaNO2 by simple heating of NaNO3.
I used a 50ml quartz crucible, which I find to be a very useful piece of equipment. They are thermally indestructible, you can heat them to red heat
and dunk them in cold water without any risk of cracking.
I melted some NaNO3 and heated it until it was bubbling at a slow but steady rate. It was held at this temperature for 20 minutes.
From time to time, carefully smell the contents of the crucible and check if it begins to smell of NO2. If it does, it's too hot and the nitrite
starts decomposing to nitrogen oxides and Na2O.
Only Oxygen should be given off.
After cooling, I dissolved the residue in a small amount of water, and on addition of a few drops of HCl, it fizzed vigorously and lots of brown fumes
were given off. I was surprised at how much gas was produced.
This method only produces a nitrite/nitrate mix, but the abovementioned separation procedures can of course be applied.
This seems like the "cleanest" preparation of nitrites to me.
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bio2
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Drying Sodium Nitrite
As this seems to be the primary Sodium Nitrite thread I put the simple question here which I couldn't find searching.
What is the preferred method of drying NaNO2?
Just got some 99.1% recently and it seems a little damp! Also just how hygroscopic is this stuff?
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