My grandfather was a big fan of the old sitcom Hogan’s Heroes, and to some extent, I’ve inherited his taste in comedy. The episode which sticks out in my mind the most, centers around a heavily guarded barrel of water. Numerous rumors circulate about why the barrel of water is so important, including one that the water is from the Fountain of Youth, but eventually it is revealed that the barrel simply contains “heavy” water. Prior to my days as a student of chemistry, this begged the question: what makes the water so “heavy”?
You may be aware that a molecule of water consists of three atoms: two hydrogen atoms and one oxygen atom. Water becomes “heavy” when the hydrogen atoms in water are substituted with a rare isotope of hydrogen. In case you’re not familiar with isotopes, you can think of isotopes as being the same basic building blocks of a molecule, only with a tiny bit of extra mass. This brings me to our main topic of discussion: deuterium.
Both deuterium (D) and hydrogen (H) consist of one electron and one proton, but deuterium also has a neutron, which is what provides the extra mass in heavy water. More succinctly, it can be said that deuterium is an isotope of hydrogen. This subtle subatomic difference is all that distinguishes heavy water (D2O) from regular water (H2O), but the unique properties of D2O permit a myriad of applications in chemistry and physics. (more…)