Explosive properties Nitromethane was not known to be a high explosive until a railroad tanker car loaded with it exploded on June 1, 1958.[5] After
much testing it was realized that nitromethane was a more energetic high explosive than TNT, although TNT has a higher velocity of detonation and
brisance. Both of these explosives are oxygen poor and some benefits are gained from mixing with an oxidizer, such as ammonium nitrate. Pure
nitromethane is an insensitive explosive with a VoD of approximately 6,400 m/s (21,000 ft/s), but even so inhibitors may be used to reduce the
hazards. The tank car explosion was speculated to be due to adiabatic compression, a hazard common to all liquid explosives. This is when small
entrained air bubbles compress and superheat with rapid rises in pressure. It was thought that an operator rapidly snapped shut a valve creating a
"hammer-lock" pressure surge. Nitromethane can be sensitized by adding a base to raise the pH. Nitromethane can also be mixed with ammonium nitrate,
which is used as an oxidizer, to form an explosive mixture known as ANNM. One graphic example of this was the use of nitromethane and ammonium nitrate
in the Oklahoma city bombing. It is also miscible with concentrated nitric acid, forming an explosive composition with similar power and sensitivity
to nitroglycerin.
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