The heats of formation for a reaction containing explosive chemicals can be described as the total heat evolved when a given quantity of a substance is completely oxidized in an excess amount of oxygen, resulting in the formation of carbon dioxide, water and sulfur dioxide. For explosive substances which do not contain sufficient oxygen in its molecule for complete oxidation, i.e. TNT, products such as carbon monoxide, carbon and hydrogen gas are formed. The energy liberated during the formation of these products is known as the heat of explosion . If these products are then isolated and allowed to burn in excess oxygen to form substances like carbon dioxide, water, etc., the heat evolved added to the heat of explosion would be equal to the heat of combustion . Consequently, the value for the heat of combustion is higher than the value for the heat of explosion for substances which have insufficient oxygen for complete oxidation. For explosive substances with positive oxygen balances, i.e. nitroglycerine, there is generally no difference between the value for the heat of explosion and that of the heat of combustion.

The value for the heat of formation can be negative or positive. If the value is negative, heat is liberated during the reaction and the reaction is exothermic; whereas, if the value is positive, heat is absorbed during the reaction and the reaction is endothermic. For reactions involving explosive components the reaction is always exothermic. In an exothermic reaction the energy...