Preparation of an Explosive: NI
3
.NH
3
Anjana Adhikari
CHE 302L

Abstract:
Nitrogen triiodide ammoniate (NI
3
.NH
3
) with explosive nature was prepared in the laboratory from the mixture of 101 mg iodine and 1 mL of 30% (15.1 mM) concentrated ammonia hydroxide. The dry red-brownish product NI
3
.NH
3
when brought in contact with the yard stick was supposed to detonate but it didn’t for the experiment conducted.
Introduction:
Bond order is the number of chemical bonds between atoms in a molecule. The high the bond order, the stable is the compound as the atoms are held closer tightly with the attraction to each other. When the distance between the atoms decreases, the compound experiences steric strain.
Nitrogen occupies 78% by volume of the earth’s atmosphere and is a constituent of all living beings. It is unreactive. Nitrogen has a melting point of -209.86
°
C and a boiling point of -195.8
°
C.
Nitrogen is used to prevent oxidation, as inert diluter for reactive gases and as an inhibitor of fire or explosions.
1
It is also used in the metal industry and has applications in welding, brazing, and soldering. Nitrogen is used as a propellant gas for aerosol cans as it is nonreactive by nature. The liquid nitrogen has an important cryogenic use.
Nitrogen has an electronic configuration of 1s
2
2s
2
2p
3
thus has only 3 shells and forms short bonds to other atoms. The strong triple bond present between the nitrogen-nitrogen interaction with the energy of 266 kilocalories per mole in the gaseous state of nitrogen makes the formation of inorganic nitrogen compounds difficult
1
. There is an exception to the norm as weak N-H single bonds are formed and they form nitrogen-based compounds like ammonia. Compounds with the nitrogen-nitrogen single bond are unstable due to lone pair-lone pair repulsion and have explosive consequences due to the instability.

Ammonia is an inorganic compound of nitrogen and hydrogen and is one of the most abundant chemical nitrogen-containing compounds with N-H bond 2 . It is highly soluble in water and forms ammonium hydroxide. Ammonia is a neurotoxin and metabotoxin. Longer exposure to ammonia causes health hazards like eye irritation, skin irritation, sinusitis, interstitial lung, and upper airways irritation. Small amounts of ammonia are present inside the vertebrate organism.
2
The boiling point of ammonia is -33.34
°
C. Ammonium hydroxide (NH
4
OH) is harmful to the throat, skin, and nose if inhaled or absorbed.
The molar concentration of the hydrated ammonia used in the reaction can be calculated using equation 1. 𝑠𝑜𝑙𝑢𝑡𝑒 𝑚𝑎𝑠𝑠 𝑖𝑛 𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑔
𝑋
1 𝑚𝑜𝑙 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑔𝑟𝑎𝑚 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒
𝑋 𝑑𝑒𝑛𝑖𝑡𝑦 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑔
𝐿
= 𝑚𝑜𝑙𝑒𝑠
𝐿
(1)
Iodine is a diatomic non-metal. It has a melting point of 113.5
°
C and boiling point of 184.3
°
C.
Iodine with alcohol is used as a disinfectant and it is important in photography and nutritional diet.
Iodine in solid state is not reactive with nitrogen. It has a pungent odor and is corrosive in nature.
Nitrogen triiodide ammoniate (NI
3
.NH
3) is prepared in the lab from the mixture of iodine and aqueous ammonia.
𝐼
2
+ 𝑁𝐻
3
→ 𝑁𝐼
3
. 𝑁𝐻
3
(2)
Nitrogen triiodide was first discovered in 1990 as a byproduct when boron nitride reacted with iodine monofluoride and was first characterized by the Raman spectroscopy.
4
𝐵𝑁 + 3 𝐼𝐹 → 𝑁𝐼
3
+ 𝐵𝐹
3
(3)

𝑁𝐼
3
is unstable so it decomposes with an explosive effect. The process of formation of nitrogen triiodide is endothermic and the decomposition of it to nitrogen and iodine is exothermic which makes the explosion happen 4 . The purple vapor during explosion is the iodine vapor and is hazardous if inhaled. NI
3
has no practical use as when it dries it detonates easily whenever you try to use it or touch it with anything dry
4
forming nitrogen and iodine vapor.
2 𝑁𝐼
3
(𝑠) → 𝑁
2
(𝑔) + 𝐼
2
(𝑔) (4)
The actual decomposition equation looks like the equation (5) as the ammonia is always attached with 𝑁𝐼
3
.
8 𝑁𝐼
3
. 𝑁𝐻
3
(𝑠) → 5 𝑁
2
(𝑔) + 6 𝑁𝐻
4
𝐼(𝑠) + 9 𝐼
2
(𝑔) (5)
It can be only stable when in preparatory phase at moist conditions. It is a great compound for fun explosive experiments within the hood of the lab.
Methods:
The solid form of iodine was weighted using the analytical balance. 101 mg of the iodine measured was added to a 10 mL beaker and a small stirring rod was added to stir the mixture. The beaker was placed above the magnetic stirring hot plate in the air-ventilated hood and 10 mL of the 30% ammonium hydroxide was added to the beaker. The stirring of the suspension mixture solution was started and kept constant at 350 rpm for 25 minutes. When most of the liquid evaporated, the moist reddish-brown product was transferred over a filter paper and left to completely dry in another hood with open space. Once the explosive product was dry, a yardstick was used to tap the product to detonate it.

Results and Discussions:
The color of the mixture turned from black to yellow on continuous stirring. The product which was dried for an hour and half when brought in contact with the yard stick did not explode or produce any vapor. Thus, the detonation of the product was not successful. The reason behind the product not exploding might be the use of lower concentration of the ammonia solution. The available ammonia solution was only 30% concentrated which was 15.1 mM by concentration. If the hydrated ammonia of higher concentration was used or if the higher amount of iodine was used, the expected results might have been obtained.
30𝑔 𝑁𝐻
3
100𝑔 𝑤𝑎𝑡𝑒𝑟
𝑋
1 𝑚𝑜𝑙 𝑁𝐻
3
17.03052 𝑔 𝑁𝐻
3
𝑋
0.89801 𝑔 𝑁𝐻
4
𝑂𝐻
𝐿
= 0.0158 𝑚𝑜𝑙
𝐿
= 0.158 𝑀 = 15.1 𝑚𝑀 (5)
Questions Answered:
1.
8 𝑁𝐼
3
. 𝑁𝐻
3
→ 5 𝑁
2
+ 6 𝑁𝐻
4
𝐼 + 9 𝐼
2
2.
Fluorine has similar size to nitrogen whereas chlorine is bigger than nitrogen and has bigger orbital size which establishes a very weak bond between the nitrogen and chlorine.
Similarly, nitrogen has comparatively higher electronegativity than chlorine atoms while
Fluorine has the highest electronegativity. So, a strong bond is established between the atoms with higher electronegativity than that with the atom with low electronegativity.
3.
Nitrogen has linear geometry with sp3 hybridization while phosphorous has tetrahedral molecular geometry with sp3 hybridization. The electronic configuration of nitrogen is
[He] 3s
2
3p
3
and that of phosphorous is [Ne] 3s
2
3p
3
. Phosphorous is bigger in shape due

to the presence of extra shells. Similarly, the electronegativity of phosphorus is 2.19 whereas that of nitrogen is 3.04. The triple bonds between N-N is stronger than P-P and the single bond of P-P is much stronger than N-N single bonds. All these factors result into difference in structure of the nitrogen and phosphorous though they fall in the same group.
4.
Nitrogen has 5 valence electrons and 10 in total when two nitrogen atoms bond together.
To satisfy the octet rule, the nitrogen-nitrogen atoms must have a triple bond in between.
Triple bonds attract the two nitrogen atoms to each other strongly and make them very stable. In case of single bond between nitrogen-nitrogen atom, the octet rule is not followed or none of the atoms attain octet state and the single bond doesn’t attract the atoms closer together, so they are unstable and weak.
5.
The explosive reaction must be initiated, it should go quick and must produce gas or heat.
6.
Bond order of:
N
2
: (10-4)/ 2 = 3 N
2
+
: (9-4) = 2.5
NO : (11- 4)/2 = 2.5 NO
+
: (10-4)/2 = 3 NO
-
: (12-8)/2 = 2

References:
1.
R. Thomas Sanderson, Nitrogen, Encyclopedia Britannica inc., February 01,2019. https://www.britannica.com/science/nitrogen
2.
National Center for Biotechnology Information. PubChem Database. Ammonia, CID=222, https://pubchem.ncbi.nlm.nih.gov/compound/Ammonia (accessed on Feb. 6, 2020)
3.
http://chemistry.elmhurst.edu/vchembook/102iodine.html
4.
Cotton, Simon (2017): Nitrogen triiodide - Molecule of the Month December 2001
[Archived version]. figshare. Journal contribution. https://doi.org/10.6084/m9.figshare.5245684
.
5.
“Microscale Inorganic Chemistry: A Comprehensive Laboratory Experience”, Szafran,
Zvi; Pike, Ronald M.; Singh, Mono M., John Wiley & Sons, 1991, ISBN 0-471-61996-5,
199 – 201.