1) Bitter compound 
Bitrex is a registered trademark of Johnson Matthey-Macfarlan Smith of Edinburgh Scotland for the product Denatonium Benzoate. This synthetic chemical is extremely bitter and detectable to humans at 0.05 ppm (50 ppb). Macfarlan Smith chemists discovered this product in 1958 during research on derivatives of the local anesthetic lidocaine. In 1960 ...