Where does all this chlorine come from? I can literally see tons of it out my window. Elemental chlorine does not exist naturally on our planet but is manufactured by electrolysis of seawater. The vast deposits of salt created during millions of years of continental upheaval and slow evaporation of the ancient Lake Bonneville are mined on the shores of the present-day Great Salt Lake. Through elaborate extraction procedures, the various chloride salts can be separated. Some of this salt ends up on your french fries (NaCl), and some you throw on your sidewalk in the winter (CaCl2). The MgCl2 is electrolyzed to produce Mg0, a lightweight metal used in the auto industry. Of course, the by-product of magnesium production is elemental chlorine, which can be responsibly used for all of the above-mentioned health and manufacturing applications.