I do think it is possible that through chemistry something could be invented that could induce the effect you are proposing (Greek Fire was invented in a comparable time and concentrated strong acids and bases were being manufactured and used at least as early as the medieval times). I wonder if this is not something that they would have thought to develop as a society, though. Given the abilities granted by stormlight (radiants, fabrials, etc.) it seems like they have invested much more study into fabrial engineering and harnessing stormlight to do things for them than chemistry. A lot of their problems may have been more easily solved through investiture than through traditional STEM fields. Maybe it is my background, but we don't see a lot of study of chemistry, physics, or biology in Roshar. Shallan seems to be one of the few people interested in biology given just about everything she observes she is coming up with theories about instead of having already learned them. All the brightest minds are busy investigating interesting things like fabrials and realmatics and not bothering with boring things like chemistry...