2. ATMOSPHERE

The oxidizer in the atmosphere is free fluorine (F₂) in a rather low concentration, about 4 or 5 percent. With it appears a mad collection of gases. There are a few inert diluents, such as N₂ (nitrogen), argon, helium, neon, etc., but the major fraction consists of CF₄ (carbon tetrafluoride), BF₃ (boron trifluoride), SiF₄ (silicon tetrafluoride), PF₅ (phosphorous pentafluoride), SF₆ (sulphur hexafluoride) and probably others. In other words, the fluorides of all the non-metals that can form fluorides. The phosphorous pentafluoride rains out when the weather gets cold. There is also free oxygen, but no chlorine. That would be liquid except in very hot weather. It sometimes appears combined with fluorine in chlorine trifluoride. The atmosphere has a slight yellowish tinge.