# Is there a simple and inexpensive way to generate nitrogen gas?

It's fairly easy to generate a significant yield of hydrogen gas simply by reacting zinc metal with $\ce{HCl}$ or aluminum with $\ce{NaOH}$ solution. But is there a simple and inexpensive chemical reaction that generates a significant yield of pure nitrogen gas?

• Liquid nitrogen is rather available, I think from welding supply stores. Some tire stores inflate tires with nitrogen and will have compressed gas available. – Ross Millikan Dec 17 '14 at 4:31
• @trb456 really had the best answer regarding this question as I don't consider heating or even working with azides as a safe and practical means. The potential $NO$ and $HNO_3$ byproducts are poisonous and so its probably a good idea to provide the means suggested to scrub these gases from the gas produced. – docscience Dec 17 '14 at 20:54

Per Wikipedia, we have this laboratory method:

$$\ce{NH4Cl(aq) + NaNO2(aq) → N2(g) + NaCl(aq) + 2 H2O (l)}$$

Also per Wikipedia, this method generates small quantities of impurities of $$\ce{NO}$$ and $$\ce{HNO3}$$, which can be eliminated by passing the gas through potassium dichromate $$\ce{(K2Cr2O7)}$$ dissolved in sulfuric acid $$\ce{(H2SO4)}$$

Both ammonium chloride and sodium nitrite are reasonably available chemicals, and the other products (table salt and water) are undeniably safe. Sulfuric acid might a bit tougher to get depending on where you live, and potassium dichromate will be the most difficult given that the use of hexavalent chromium is discouraged (and you should research procedures to reduce the $$\ce{Cr2O7^{-2}}$$ to $$\ce{Cr2O3}$$). But otherwise, this looks like the best approach.

You could try a simple two step process. Take some air, burn some carbon-rich material in it until no further burning occurs. Then pass the remaining gas through an alkaline solution to remove the carbon dioxide. The remaining gas will be more than 95% nitrogen.

And you get this with no expensive chemicals.

• clever approach. I suppose you could increase the purity by selecting the right material to burn, and controlling the temperature. For $CO$ that might result, are there other inexpensive filtering methods that could remove it? – docscience Dec 17 '14 at 21:19
• @docscience There are lots of industrial methods (e.g. passing the gas over copper oxide) and many physical methods (if the concentration is small, activated carbon will work). – matt_black Dec 17 '14 at 21:36
• How about using an O2 scavenger, depending on the tank volume you could also get mostly nitrogen; also add a co2 scavenger for more effect. I do this at home and it works for me. – luke_mclachlan Sep 23 '17 at 17:12

One more classic method for $\ce{N2}$ preparation in the lab that hasn't been mentioned yet is oxidative dehydrogenation of ammonia to nitrogen, typically with the help of transition metal oxides, e.g.:

$$\ce{2 NH3 + 3 CuO ->[\pu{500 .. 550^\circ C}] 3 Cu + N2 ^ + 3H2O ^} \tag{1}$$

Reaction with copper(II) oxide is considered canonical and is often listed in textbooks and lab manuals, for example A Text-book of Practical Chemistry [1, p. 6] from 1921 describes this process as follows:

Nitrogen is obtained by passing air first through ·880 ammonia and then over red-hot copper turnings. The oxygen of the air is absorbed by the copper and the resulting copper oxide is at once reduced back to copper by the ammonia. The frequent renewals of the contents of the copper tube are thus entirely avoided.

\begin{align} \ce{2 Cu + O2 & = 2 CuO},\\ \ce{2 NH3 + 3 CuO & = N2 + 3 H2O} \end{align}

The gas should be washed with sulphuric acid (1 : 4) to free from excess of ammonia, and dried by strong sulphuric acid. The use of dilute acid to free it from ammonia is to avoid the danger of a great rise in temperature should a large excess of ammonia come over.

Method of obtaining nitrogen via thermal decomposition of $\ce{NH4NO2}$ is criticized as a rather inconvenient one that may potentially result in an explosion.

Small quantities of nitrogen may be prepared by carefully heating a solution of ammonium nitrite (sodium nitrite and ammonium chloride in molecular proportions). [...] The method is not recommended as it is difficult to control, and the nitrogen is generally contaminated with oxides of nitrogen, especially when the action becomes violent.

Instead, one can utilize "volcano demo" (thermal decomposition of ammonium dichromate) as somewhat safer alternative:

$$\ce{(NH4)2Cr2O7 ->[\pu{170 .. 190^\circ C}] Cr2O3 + N2 ^ + 4 H2O ^} \tag{2}$$

These days various sources provide slightly deviating techniques for reaction type (1). Other metal oxides such as $\ce{TiO2}$, $\ce{V2O5}$, $\ce{MnO2}$, their binary and ternary mixtures on silica- and alumina-supported substrates doped with rare-earths (Y, mostly) are capable of selective catalytic oxidation at lower temperatures [2, 3].

### References

1. Hood, G. F.; Carpenter, J. A. A Text-Book of Practical Chemistry; J. & A. Churchill, 1921. (Google Books).
2. Li, Y.; Armor, J. N. Applied Catalysis B: Environmental 1997, 13 (2), 131–139 DOI: 10.1016/S0926-3373(96)00098-7.
3. Gang, L.; van Grondelle, J.; Anderson, B. G.; van Santen, R. A. Journal of Catalysis 1999, 186 (1), 100–109 DOI: 10.1006/jcat.1999.2524.

There is one incredible simple, cheap and easy way to make nitrogen gas with near 99 percent purity if you don't need it compressed. I've used this method in my chemistry experiments when I needed just modest amounts of nitrogen or when I need to do reactions in the absence of reactive oxygen.

Simply buy handwarmers from Walmart or many other sources. Use a heavy duty, large resealable bag and fill it as best you can with regular, uncontaminated air. Drop the hand warmer in there and it will absorb almost all oxygen, leaving you with about 1 percent "all other gases" that are naturally in the atmosphere. Personally, I glue an airtight small rubber tube (a hose from aquarium bubblers, also found at Walmart or any pet store) then clamp it shut with a small but strong spring clamp (although other clamps will due). I've found the hand warmer can dry out before it loses its capacity to absorb O2, so I cut one end open, seal it with laundry clamps (just to keep the contents from spilling out, making a mess) and spray it LIGHTLY now and then with mist from a stray bottle. However, if your not worried about the carbon, iron powder, and table salt contained in these packets (all very harmless) you can cut the packet open and just dump it in the bottom of the bag, and spray as described above once in a while. You would be surprise how long they last and how many bags full of nitrogen you can get from just one hand warmer packet. If you're not worried about adding excess heat to your O2 purged experiment, just put the handwarmer in the bag containing the enclosed beaker. Otherwise, you can purge air out of a different bag, vessel by inserting the hose, and squeezing the nitrogen filled bag.

• How do they work? As I can see, they burn charcoal. So the result won't be nitrogen, but an $\ce{N2}$ + $\ce{CO2}$ + $\ce{CO}$ mix. – peterh Jun 19 '20 at 20:34
• (+1) This is a nice example of thinking outside the box! I am going to try it and up vote right after this is posted. Thanks! – Ed V Jun 21 '20 at 2:00

According to Wikipedia you can generate pure nitrogen by heating metal azides, which gives out nitrogen and the metal. Sodium azide is not really expensive.

$$\ce{2NaN_3 ->2Na + 3N_2}$$

However, as you may expect, this may not be a very safe reaction as the first reaction that came to my mind when you asked for a reaction with large yield of nitrogen gas is that of TNT, though that would not give a pure yield as you have required. Azides are also explosive. Sodium azide is used in car airbag and airplane escape chutes where this exact reaction is used to quickly inflate these safety features. The metallic sodium formed is then further reacted to less dangerous sodium compounds.

• This can be an extremely violent decomposition reaction. It's the reaction that generates enough gas in an instant to fill an airbag... – Jason Patterson Dec 17 '14 at 2:25
• Please nobody use this. Not only is sodium azide explosive, it's very toxic. – jerepierre Dec 17 '14 at 2:38
• Even though the reaction and the reactant are rather unpleasant, this is one of the methods that produce purest nitrogen at a lab scale. – andselisk Oct 10 '17 at 8:15
• It's also interesting that Brauer's Handbuch der präparativen anorganischen Chemie recommends this method exclusively for the nitrogen generation in the lab. – andselisk Oct 10 '17 at 14:49

To generate nitrogen you could mix potassium nitrate, hydrochloric acid, and zinc. It would generate nitrogen and the byproducts will be zinc chloride, ammonium chloride, and potassium chloride. The nitrogen would be mixed with some HCl vapors, which you could remove through bubbling it in water.

The combustion of dinitrogen monoxide can also produce nitrogen.

Thermal decomposition of ammonium nitrite: $$\ce{NH4NO2 -> N2 + H2O}$$

• Please elaborate more. At Chem.SE, we like answers to include reasoning and explanation, otherwise they are likely to be downvoted and/or deleted. – Jan Aug 28 '17 at 10:31
• I guess it's worth mentioning that solid ammonium nitrite decomposes with an explosion. – andselisk Oct 10 '17 at 8:56

Ammonium Dichromate reacted with heat produces only one gaseous product, Nitrogen. FIlter through a bubbler to get particles out of it. See Wikipedia under Ammonium Dichromate for the reaction equation and stoichiometry.

• It's considered a good practice to include an actual reaction, conditions and original source (use ACS bibliography style) in your question. Avoid citing encyclopedias and link-only answers. Also, chemical names are generally starting with low-case letters unless it's a first word in a sentence. – andselisk Oct 10 '17 at 7:18