So I was resting on my oars in the blogosphere waiting for something to happen when over the horizon loomed a (British) Independent link to a compendium of fact(oid)s about 42. Facts like: "The atomic bomb that devastated Nagasaki, Japan, contained the destructive power of 42 million sticks of dynamite." That made me reasonably confident that Fat Man released energy equivalent to either 42 or more likely 21 kilotons of TNT (this is the standard comparative measure of explosive power) and the usual sources revealed this to be so. The same train of reasoning circled on the fact that a stick of dynamite weighs a kilogram or more likely 500g.
But this confidence hinged significantly on the assumption that the journo who wrote the article had been educated in the Arts Block. Because TNT isn't the same as dynamite. It's much less powerful: 2.8 megajoules/kilogram compared to dynamite's 7.5MJ/kg. What he should have said was "...destructive power of 14 million sticks..." and then gone off back to google to find a different 42-fact because the Nagasaki line was a bust.
C7H5N3O6 shows that it has proportionately much less oxygen than the related compound tri-nitroxy-propane C3H5N3O9 aka nitroglycerine which is the active principle in dynamite. This means that combustion is less efficient - hence its lower MJ/kg. Chemical reactions are usually complex but chemists like to summarise them with formulae - and insist that budding chemists add up the atoms on each side of the arrow to ensure they have accounted for everything. Here's what they think happens when TNT goes up:
- 2 C7H5N3O6 → 3 N2 + 5 H2O + 7 CO + 7 C and/or
- 2 C7H5N3O6 → 3 N2 + 5 H2 + 12 CO + 2 C
Thar she blows!! One minute you're safe in a warm bath of truthiness on a Douglas Adams tribute site and an hour later you bob up with hearing loss in a remote pond in Hawaii wondering if Halocaridina rubra is edible.