Untreated peroxide mix explodes
An attempt to prepare a sulphoxide from sulphide and hydrogen peroxide - the reaction mass was reduced by half on a rotavap, and then left standing in fume cupboard to cryst, after 5 hours the flask exploded. Probably caused by over-pressurization due to decomposition of excess peroxide - This should have been destroyed before the rotavap operation.
In a second incident at another company, an attempt was being made to make a sulphoxide from a phenothiazine antihistamine salt, after some weeks a crop of sulphoxide was removed, the filtrate was boiled down somewhat and allowed to stand, some months later a second crop of solid was isolated, in an attempt to get more solid, some acetone was added to try to precipitate product, when this failed, the mix was allowed to stand for some time, then evaporated down some more, when reduced to half volume the flask was removed, within a few minutes the flask was seen to be "filling with foam" so personnal were removed to a safe distance, and the flask was observed. The flask contents continued to gain in volume and come to the boil, at which point there was a large woosh, the flask contents glowed red and the lab was entirely filled with smoke. In the case it was apparent that the use of acetone had generated an unstable peroxide.