What makes nitroglycerin so dangerous?
The second compound we shall use in comparison is hexogen (known as ‘ RDX, ’ standing for ‘ Research Department Explosive ’ ), more powerful than TNT and widely used in military applications:
Skeletal formula of RDX
Image Source: Wikipedia RDX
A compound’s oxygen balance is obtained through the following formula: 6
−1600 𝑀𝑟 𝑜𝑓 𝐶𝑜𝑚𝑝𝑜𝑢𝑛𝑑
𝑌 2
𝑂𝑥𝑦𝑔𝑒𝑛 𝐵𝑎𝑙𝑎𝑛𝑐𝑒(%) =
× (2𝑋 + (
) + 𝑀 − 𝑍)
Where X is the number of atoms of carbon, Y is the number of atoms of hydrogen, M is the number of atoms of metal, and Z is the number of atoms of oxygen. The formula ‘ works ’ because (2𝑋 + ( ) + 𝑀 − 𝑍) determines the number of oxygen atoms which are either deficient or in excess for converting all carbon to CO 2 , all hydrogen toH 2 O, and all metal atoms to ametal oxide. This number is thenmultiplied by the percentage value of the mass one atom of oxygen takes up in the molecular mass of the compound. Hence, we find the number of excess atoms of oxygen liberated from the molecule, expressed as a percentage of the mass of the molecule. Now let’s see how the oxygen balance of nitroglycerin compares to those of other molecules, starting with TNT. TNT has the chemical formula C 7 H 5 N 3 O 6 and a relative molecular mass of 227, and so we can calculate its oxygen balance as follows: 𝑌 2
−1600 227
5 2 ) − 6) = −74.0%
× (2(7) + (
This indicates that there is insufficient oxygen for the complete oxidation of the decomposition products, and as a result, less energy will be released in the explosion than would be released if more oxygen were present in the molecule. It is for this reason that TNT is rarely used on its own, but is often mixed with an oxidizer such as ammonium nitrate, which helps to ensure complete oxidation and reduce smoke and toxic by-products. The specific mixture of TNT and ammonium nitrate is known as Amatol; this was widely used during the Second World War. 7
6 See S2S Oxygen Balance. 7 See Encyclopaedia Britannica Detonating Cord.
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