First question: how old was the flask? I’ve broken borosilicate flasks and beakers under gentle heating before where new ones would be able to
handle it well. If it happened to be dropped (even just a ruler’s length) at some point then there may have been imperceptible cracks which
could’ve propagated under stress. A perfect, well made flask should not break under most synthesis conditions, like I’ve dumped sulphuric acid
into water within borosilicate glassware and hit them with an ‘ungauzed’ flame, and they tolerate the fast heating. |