A flux (derived from Latin Fluxus meaning "flow") is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining. Some of the earliest known fluxes were sodium carbonate, potash, charcoal, coke, borax, lime, leads sulfide and certain minerals containing phosphorus. Iron ore was also used as a flux in the smelting of copper. As cleaning agents, fluxes facilitate Solderig, brazng, and welding by removing oxidation from the metals to be joined.