Lucite Cube // Fluorine

While most people associate fluorine with the fluoride in toothpaste, the pure form of this element has a lethal bite. The gas is so reactive that its atoms will form near unbreakable bonds with just about any other element. In fact, fluorine holds the record for most difficult element to separate. The scientist who finally managed the feat won the Nobel prize for his efforts and was lauded by the awards panel for having "tamed the savage beast."

Fluorine's savagery extends to glass itself. So much so that the very dangerous hydrofluoric acid is actually used to etch designs into glass, because it's so reactive. Luckily, fluorine also reacts with calcium to form a transparent mineral called fluorite. Usually sold as pretty, purplish diamond-shaped stones in rock shops, fluorite is actually clear in the absence of any impurities, and a thin coating in glass tubing is enough to trap the gas from further misbehaving. Helium is also added to help prevent unwelcome reactions inside the ampule.