The key chemical in the process is ammonium fluoride (NH 4 F). It’s possible to use the salt directly in a molten form, but heating it invariably leads to some production of hydrogen fluoride, which is extremely dangerous stuff (although they end up using some later). So instead, they used it dissolved in water, which apparently keeps these reactions from occurring. In this process, heating the solution to about 70° C results in the formation of NH 4 F 2 ions, releasing ammonia gas that’s used later in the process. This ion donates a fluorine to the lithium, leaving a water-based solution of lithium fluoride. The silicon also forms a soluble ion, (NH 4 ) 2 SiF 6 ), while the aluminum forms a similar ion that remains behind as a solid, (NH 4 ) 3 AlF 6 ). Each of these is processed separately. Using everything We’ll start with the aluminum chemistry, which is one of the simpler pathways.…