The mouse and the expensive nuclear cocktail

The first pure sample of heavy water (D₂O  −  water containing only deuterium, an isotope of hydrogen and oxygen) was produced in 1933 by Gilbert Lewis, an American chemist, using electrolysis. To determine if it was harmful to living things, Lewis fed his entire supply of heavy water, a total of 1 cm³, to a mouse. Though the mouse survived, it was reported to have shown “marked signs of intoxication”. Lewis’ American colleague Ernest Lawrence, who was waiting to use the heavy water in his cyclotron, commented: “This was the most expensive cocktail that I think mouse or man ever had.”