Sciencemadness Discussion Board - Preparation of Sodium Nitrite NaNO2

Preparation of Sodium Nitrite NaNO2

Dionysus12 - 9-7-2011 at 09:18

Hello everyone,

I've been meaning to make or procure some sodium nitrite which has suddenly become very hard to find in my country. I was thinking of reacting HCL with KNO3 and passing the fumes through a bath of aqueous NAOH but I wasn't sure about how to go about seperating the products. Any advice?

barley81 - 9-7-2011 at 09:45

Please use the search engine before asking. There was a thread on the topic. Here it is:
http://www.sciencemadness.org/talk/viewthread.php?tid=52
and here is a method I think is nice:

Quote: Originally posted by Polverone

The other night I was looking at Muspratt volume 1 under "nitrous ether" (ethyl nitrite) and I found what seems like an interesting, simple method. Mix 100 parts of very fine KNO3 with 12.07 parts of lampblack (I'm guessing any finely divided carbon would work - I hope so), heat it in a crucible, and cover it and remove it from the heat source when the reaction is concluded (http://bcis.pacificu.edu/~polverone/muspratt1/c-834.html). According to the book some carbonate is formed but it is mostly pure enough to be used as-is (at least by the standards of 1860). It also mentions the formation of silicate - not sure if this is because they started with impure KNO3 or because of the crucible's composition. I am going to try this soon, not because I need more nitrite but because every other preparative method I've come across has been such a pain.

BTW, kingspaz, what physical form is your aluminum in? Powder, granules, foil, wire?

[Edited on 18-2-2003 by Polverone]

edit:
I only picked that method because the reactants are cheap and it's a little easier (for a few g of nitrite-containing slag).

[Edited on 9-7-2011 by barley81]

AndersHoveland - 9-7-2011 at 10:53

KNO3 is not going to react with HCl, at least not in water (it might be possible to use DMSO or an ionic liquid as the solvent). Assuming you can get the KNO3 to dissolve, anhydrous HCl gas could be bubbled in and the reaction would probably be:
KNO3 + (4)HCl --> KCl + (2)H2O + NOCl + Cl2
Bubbling the gas products into a solution of NaOH will not give any nitrites, because the chlorine would oxidize them to nitrate.
NaNO2 + H2O + Cl2 --> NaNO3 + (2)HCl [aq]
Possibly it would work if there was also thiosulfate in the solution to immediately reduce the chlorine, but not sure.

The reduction of sodium nitrate to nitrite with carbon is not efficient and gives low yields. Much higher yields of nitrite can be obtained by using molten lead instead. Alternatively, 25% concentrated nitric acid can react with copper to give off nitrogen-oxide fumes that can then be bubbled to an alkaline solution to form nitrites. Do not use higher concentration of HNO3, as then mostly nitrogen dioxide will form which will reduce yields.
(2)NaOH + NO2 + NO --> (2)NaNO2 + H2O

Remember that both nitric oxide (NO) and solutions of sodium nitrite (NaNO2) are oxidized by the air, to brown NO2 and NaNO3, respectively.

Tiberius_C - 10-7-2011 at 02:22

Other than reacting with carbon, you might want to try warming a small quantity to just past decomposition temp -- should yield NaNO2

Dionysus12 - 10-7-2011 at 04:22

Thanks for the help, I might try the carbon route after hitting the books for a bit. I tried using the search function but I couldn't find anything relevant for some reason.

Magpie - 10-7-2011 at 06:25

http://www.sciencemadness.org/talk/viewthread.php?tid=52&...

Dionysus12 - 10-7-2011 at 07:46

Thanks Magpie, the pictures are very helpful

Chemistry Alchemist - 25-8-2011 at 22:35

Heating up Nitrates make them loose a oxygen molecule forming NO2 (2NaNO3 -> 2NaNO2 + O2?)
just a guess, remember reading up on it a year back

redox - 26-8-2011 at 06:37

Quote: Originally posted by Chemistry Alchemist

Heating up Nitrates make them loose a oxygen molecule forming NO2 (2NaNO3 -> 2NaNO2 + O2?)
just a guess, remember reading up on it a year back

I think that reaction only occurs smoothly in the presence of a reducing agent, such as carbon or lead. If it were as simply as you made it seem, there wouldn't be huge threads on the topic.

Chemistry Alchemist - 22-9-2011 at 06:24

Could you heat up a test tube or beaker of sodium nitrate, mix it with some Carbon and heat it up? (NaNO3 + C = NaNO2 + CO) is this possible? sorry if its wrong... im just reading different forums and putting things together

[Edited on 22-9-2011 by Chemistry Alchemist]

ScienceSquirrel - 22-9-2011 at 07:18

I have made potassium nitrite of I believe to be reasonable purity by melting potassium nitrate (mp 334 C ).
It melts to a clear liquid that gradually loses oxygen and solidifies as it forms the nitrite (mp 440 C).
In my opinion this is easier than trying to make the sodium salt as the melting points of sodium nitrate and sodium nitrite are 308 C and 271 C respectively.
A solution of the product was only weakly basic and addition of a solution of the product to a solution of dilute sulphuric acid and ferrous sulphate gave a strong brown ring.

[Edited on 22-9-2011 by ScienceSquirrel]

AndersHoveland - 22-9-2011 at 11:44

Quote: Originally posted by ScienceSquirrel

I have made potassium nitrite of I believe to be reasonable purity by melting potassium nitrate (mp 334 C ).
It melts to a clear liquid that gradually loses oxygen and solidifies as it forms the nitrite (mp 440 C).
In my opinion this is easier than trying to make the sodium salt as the melting points of sodium nitrate and sodium nitrite are 308 C and 271 C respectively.

This is very interesting. My only question would be what portion of the potassium nitrate can be converted to nitrite by heating. Potassium nitrate begins to decompose at a relatively low temperature, but it was my understanding that it is mostly an incomplete decomposition unless much higher temperatures are reached. That is to say that only a very small portion of the sample being heated will turn into nitrite.

[Edited on 22-9-2011 by AndersHoveland]

Alastair - 29-11-2011 at 13:41

4189. Nitrite of Potassa. It is obtained
mixed with a little nitre and potash by
heating nitre to redness. To purify the
residuum, dissolve it in boiling water, set
aside for 24 hours, pour off the liquid from
the deposited nitre, neutralize the free alkali
with acetic acid, and add twice its volume of
alcohol. In a few hours more, nitre crystallizes,
and the liquid separates into two layers ;
the upper is alcoholic solution of acetate of
potash, the lower is solution of nitrate of
potash, which may be evaporated to dryness,
or kept in solution. (Bcasley.)

Or, pass nitrous acid gas, formed by acting:
on 1 part of starch with 10 of nitric acid,
through a solution of caustic potash, specific'
gravity 1.38, until it becomes acid ; then add'
a little caustic potash, so as to render it distinctly
alkaline. It may then be kept in the
liquid form, or evaporated to dryness. ( Corenwinder) <-- this works good only in VERY basic conditions.

AJKOER - 3-12-2011 at 09:18

Here is an untried but interesting theoretical process to produce small quantities of NaNO2. On a prior Sciencemadness thread:

http://www.sciencemadness.org/talk/viewthread.php?tid=6650

it was noted that NH4NO2 can be formed by the oxidation of a small quantity of NH4OH with H2O2 in the presence of Na2CO3 or NaOH or Zn dust or Pt.

2NH4OH + 3H2O2 --catalyst-> NH4NO2 + 6H2O

So just add NH4OH to say Sodium Percarbonate, 2Na2CO3 . 3H2O2 (found in household chlorine free bleach, but conform to local laws) and bring to a boil (caution, I would not rule out the possibility of an explosion or toxic fumes upon full evaporation). The presence of the nitrite can be reputedly demonstrated upon adding H2SO4 to form NO and NO2:

2 NH4NO2 + H2SO4 --> (NH4)2SO4 + 2 HNO2

2 HNO2 --> NO + NO2 + H2O

I suspect that in the presence of Na2CO3 some NaNO2 could be formed:

2 NH4NO2 + Na2CO3 --> (NH4)2CO3 + 2 NaNO2

the reaction moving to the right as the Ammonium carbonate decomposes upon heating at 58 C into NH3, CO2 and H2O (NaNO2 only decomposes above 320 C).

Also, it is likely that some of the NH4NO2 will decompose upon heating in water:

NH4NO2 + H2O --> N2 + 2 H2O

Note, the formation of NaNO2 is generally desirable given the explosive properties of NH4NO2 (both thermal detonation between 60 to 70 C and shock sensitivity), its 2 hour half-life, and its acutely toxic nature.

[Edited on 3-12-2011 by AJKOER]

[Edited on 3-12-2011 by AJKOER]

Nitro-esteban - 21-7-2013 at 16:44

I came up with this equation according to some info I got from wikipedia: 2NH3 + 3 H2O2 = NH4NO2 + 4 H2O.

Im thinking that maybe barium nitrite could be made by reacting barium nitrate with ethanol.

subsecret - 21-7-2013 at 18:54

Quote: Originally posted by AndersHoveland

KNO3 is not going to react with HCl, at least not . . .

I've heard that KNO3 + Cu + HCl will react to form NO2.

SM2 - 22-7-2013 at 06:43

Just do the litherage (Pb) starting with the NO3+. It consistently works, and the red and yellow lead oxides can be recycled, or used elsewhere.

AMchemistry - 26-7-2013 at 18:04

you can heat up the NaNO3 to decompose it to NaNO2

AndersHoveland - 27-7-2013 at 15:15

reduction of nitrates to nitrites using molten lead
see attachments

ElectroWin - 27-7-2013 at 15:40

if you needed food grade nitrite, dont use the lead process

AndersHoveland - 27-7-2013 at 18:54

If sodium nitrate is dissolved in concentrated hydrochloric acid, an equilibrium is established:

NO₃^‒ + 3 Cl^‒ + 4 H⁺(aq) <==> 2 H₂O + NOCl + Cl₂

Under strongly acidic conditions, the hydrochloric acid can reduce the nitrate. If such a mixture is heated to boiling and distilled, the fumes could be passed into a solution of ferrous sulfate, FeSO₄, resulting in nitric oxide. That nitric oxide could then be bubbled, along with a limited amount of air into a third solution containing sodium bicarbonate, to neutralize the mixed nitrogen oxides, resulting in sodium nitrite.

Assuming the solution is not too acidic, nitrosyl chloride hydrolyzes into dilute hydrochloric and nitrous acids:

NOCl + H₂O --> HNO₂ + H⁺(aq) + Cl^‒

2 Fe²⁺(aq) + Cl₂ --> 2 Fe³⁺(aq) + 2 Cl^‒

Iron(II) salts will not reduce nitric oxide, but they will reduce nitrogen dioxide to nitric oxide.

Nitric oxide oxidizes on contact with air to nitrogen dioxide. If an equal volume mix of these gases (1 part NO2, 1 part NO) are passed into an alkaline solution, nitrite will form.

2 NaOH (aq) + NO₂ + NO --> 2 NaNO₂ + H₂O

Of course, for maximum efficiency (and purity), we do not want all of the NO converted into NO2. Let us look at what would happen if too much NO2 was allowed to react...

2 NaOH (aq) + 2 NO₂ --> NaNO₃ + NaNO₂ + H₂O

If the proportion of NO2 is too great relative to the amount of base in solution, none of the NO will be absorbed, and no nitrite will be able to form.

NaNO₂ + NO₂ --> NaNO₃ + NO

Furthermore, your newly made solution of sodium nitrite needs to be kept away from air, because it will oxidize.

So, it is important to make sure that too much air is not allowed to react, and it may be best to use a slight excess of base. Sodium nitrite crystallizes as white cubic crystals, so it is fairly easy to identify.

An alternative way, without using air, would be to use dilute nitric acid to convert some of the nitric oxide into nitrogen dioxide. This would require a fourth solution in the setup. Get out all your stoppers and tubing! (Did I mention that NO2 can be a bit corrosive to rubber hoses?)

2 NO₃^‒ + 2 H⁺(aq) + NO --> H₂O + 3 NO₂

Normally the nitrate ion is fairly inert to reduction, but nitric oxide is a reactive radical that can catalyze many reactions. A little acid is required, however. If conditions were alkaline, just the reverse reaction would occur, NO2 can oxidize nitrite to nitrate.

Solutions of nitrous acid exist in equilibrium with nitric oxide and nitrogen dioxide. Furthermore, nitrogen dioxide is considered a mixed acid anhydride because in water it reversibly hydrolyzes into nitrous and nitric acids.

I am not sure, you may just be able to get the concentrated hydrochloric acid, nitrate salt, and iron(II) salt to all react together to directly give off the nitric oxide. And then carefully bubble this into the bicarbonate solution along with a small flow of air, being very careful only to let in a very small amount of air. Combined, the two equations would look like this:

NaNO3 + 3 HCl + 3 FeCl2 --> NaCl + 3 FeCl3 + NO

4 NO + O2 + 2 NaCO3H --> 2 NaNO2 + H2O + 2 CO2

[Edited on 28-7-2013 by AndersHoveland]

AJKOER - 31-7-2013 at 04:14

To confirm Andershoveland's last equation,

4 NO + O2 + 2 NaHCO3 --> 2 NaNO2 + H2O + 2 CO2

Atomistry.com commenting on the preparation of Sodium nitrite lists one of the paths as:

"; the action of nitrous fumes containing excess of nitric oxide on a solution of sodium hydroxide or carbonate"

Link: http://sodium.atomistry.com/sodium_nitrite.html
---------------------------------------------------------------------------------------

The same source also notes:

"The Sodium nitrite, NaNO2, is obtained by reducing sodium nitrate with metals such as lead or iron, with sulphur or carbon, or with material containing these substances. In Dittrich's process the nitrate is heated with slaked lime and sawdust, the yield being almost quantitative, whereas the action of coal and graphite is too energetic:

2NaNO3 + Ca(OH)2 + C= 2NaNO2 + CaCO3 + H2O "

For those new to the literature, the comment 'too energetic' above could mean it acts like an explosive (detonates, see http://www.sciencemadness.org/talk/viewthread.php?tid=21101&... ) especially in a closed container, so be wary if attempting such a path in any significant quantities.

[Edited on 31-7-2013 by AJKOER]

Sodium nitrite

symboom - 6-10-2016 at 22:39

Sodium nitrite from ammonia on sodium percarbonate
Ammonia and peroxide form ammonium nitrite

Ammonium nitrite and sodium carbonate
With heating decomposes ammonium carbonate from solution
Into ammonia and co2 gas

[Edited on 7-10-2016 by symboom]

[Edited on 7-10-2016 by symboom]

clearly_not_atara - 7-10-2016 at 08:58

I like your idea, AndersHoveland, but I think you could avoid gases more, which is always nice when equipment is limited. Maybe you could condense most of the NOCl with some of the Cl2 in cold dichloromethane or chloroform (NOCl should have no chance of oxidizing chloroform without activation). Then passing it over eg copper, ferrous sulfate, or possibly eg oleic acid, anything that reacts heterogeneously with Cl2 could either purify the NOCl while reducing Cl2 or release NO gas.

Really I think finding something that will react with Cl2 but not NOCl is the trick. Maybe CuCl? NOCl in CH2Cl2 is a useful end-product