ammonium benzoate

Discovered in 1958, this is the bitterest-tasting compound known; as little as ten parts per million make substances unbearably bitter to most humans. It is used as an aversive agent, an additive that prevents accidental Ingestion of a toxic substance. It is used to denature ethanol, methanol, and rubbing alcohol, and well as solvents, paints, amishes,

antifreeze, etc.