Ethylene glycol

Ethylene glycol is a colourless syrupy liquid used in the production of polyester and resins, and also as an automobile antifreeze.  It has a slightly sweet taste, but is toxic and cases of poisoning are not unknown.
Ethylene glycol is almost indistinguishable from harmless glycerine, but is far cheaper.  As such, unscrupulous individuals have tried to pass it off as glycerine despite its toxicity.  One such incident in the early 20th century led to the formation of the Food and Drug Administration.
Ethylene glycol at Wikipedia
Category:Toxins