An Explosive Nitric Acid-Ethanol Mixture

A postgraduate student in a local university prepared 450 mL of an electro-polishing solution by mixing concentrated nitric acid and ethanol in a 1:2 ratio as indicated in a published research paper. The student observed "no significant temperature rise" over 3 hours, he then capped the Winchester bottle and went home. About 4 hours later, the bottle exploded, scattering glass fragments to a distance of 12 meters and with enough force to break another Winchester bottle containing oil 1.75 meters away, and a plastic shield 4 meters away. Fortunately there was no one in the laboratory at the time, otherwise the powerful explosion could have caused serious injuries.

According to Bretherick's Handbook of Reactive Chemical Hazards, such mixture is "best described as an unstable... rocket fuel mixture"! In a correspondence between the safety personnel of the tertiary institute . and the author of this well-known reference, Mr Bretherick further commented that:

These are valuable reminders for all material scientists who may need to use such etchant solutions, and in fact for all other researchers who use nitric acid for various purposes.

(This article first appeared on the June,1996 issue of SafetyWise)