Let’s start with a straightforward fact: Mercury is unimaginably toxic and dangerous. A single drop on a human hand can be irreversibly fatal. A single drop in a large lake can make all the fish in it unsafe to eat. Often referred to as quicksilver, mercury is the only common metal that is liquid at room temperature. Alchemists, including the young Sir Isaac Newton, believed it was the source of gold. In the modern era, it became a common ingredient of paints, diuretics, pesticides, batteries, fluorescent lightbulbs, skin creams, antifungal agents, vaccines for children, and of course, thermometers. There is...