By considering the structural formula of TNT (5.1) and of nitroglycerine (5.2) the proportion of oxygen in each molecule can be calculated and compared with the amount of oxygen required for complete oxidation of the fuel elements, i.e. hydrogen and carbon.

If the amount of oxygen present in the explosive molecule is insufficient for the complete oxidation a negative oxygen balance will result; this can be seen in the molecule TNT. Nitroglycerine, however, has a high proportion of oxygen, more than required for complete oxidation of its fuel elements and therefore has a positive oxygen balance. This oxygen balance can be defined as the amount of oxygen, expressed in weight percent, liberated as a result of the complete conversion of the explosive material to carbon dioxide, water, sulfur dioxide, aluminium oxide, etc.

When detonation of TNT (C ₇H ₅N ₃O ₆) takes place the explosive is oxidized to form gaseous products. Let us assume that on detonation the reactants are fully oxidized to form the gases carbon dioxide, water and nitrogen as shown in Reaction 5.1:

The equation in Reaction 5.1 needs to be balanced, and this can be done by introducing oxygen atoms (O) as shown in Reaction 5.2.

In order to balance the reaction formula for the combustion of TNT a negative sign is used for oxygen. This therefore indicates that TNT has insufficient oxygen in its molecule to oxidize its reactants fully to form water and carbon dioxide. This amount...