Complacency...can be a killer. In December 1974, I was called by the plant supervisor to come out to where the day shift was running another 2000-gal oxidation of tetrachlorocatechol using a process I'd developed for the production of high-purity o-chloranil. We had run this 15 or 20 times before without problems. The process involved use of considerably less than a stoichiometric quantity of nitric acid in hydrochloric acid under about 15 psig oxygen in the headspace. When the oxidation was complete, we centrifuged pure o-chloranil and washed the cakes with hexane..(uh oh). The problem I was presented with was that the reaction was not taking up oxygen. We checked the oxygen cylinders (OK), the dual manifold system (OK), and scratched our hard hats. 10 minutes later, the reactor exploded. Flames erupted from where the sight glass had been.
Long story short, 3 of us nearly died and it was a week before I got out of the hospital.
The graveyard shift had the job of cleaning the GL reactor, finishing the cleaning with water washes and a final spark test for explosivity.
After months of denials, the truth came out that the reactor cleaning had not been done at all and that about 100 gallons of hexane were in the reactor when the day shift loaded it for the new run. The batch sheet had been filled in as if all the cleaning and spark testing had been done. Under the agitation conditions we used and in the presence of pure oxygen, the hexane auto-ignited.
Critics will say 'well, that should teach you..." but we had been able to bypass messy recrystallizations from carbon tet using this process. We had the forms and the boxes to check but the plant workers, all good guys but a tad lazy in those eerie hours after midnight, tried cutting some corners. As Derek wrote, it all gets back to people thinking about what they're doing.This is pretty horrifying to me, for a variety of reasons. It's pretty clear that pencilwhipping the batch record was seen as an okay thing to do, which is an obvious problem (and not one that the chemist should be responsible for, said a chemist).
I wonder if the operators knew how deadly leaving hexane in the reactor was in this case. Also, I presume that a lot of development work had gone into avoiding the use of nitric acid. Yikes -- what a mess and I am glad no one died.