> Would a standard US 8 fluid oz glass of ultrapure water kill? If it would, this seems like a good mystery novel gimmick. If the pure water gimmick doesn't wo

> Would a standard US 8 fluid oz glass of ultrapure water kill? If it would, this seems like a good mystery novel gimmick. If the pure water gimmick doesn't work out, then maybe for your mystery novel switch over to heavy water, which is known to be toxic iirc. Eccentric, recluse, rich person decides to drink nothing but heavy water for the exotic allure and then dies on the eve of a corporate merger or something. Bonus points, heavy water ice cubes will sink in regular water but over time they will float because they melt off the heavy ice and refreeze regular water, changing their buoyancy. Something the eagle eyed investigator can notice in the 11th hour.