Ferrosilicon: Silica, Carbon and Scrap Iron Smelted with Bituminous Coal in an Electric Furnace (Furness, US 1,284,645)

Carbon pulls the oxygen out of silica in an electric furnace, and the silicon alloys with iron in the charge. Furness swapped part of the coke or charcoal for lumps of bituminous coal, which keep the charge open and poorly conducting, so the electrodes sit deep and the heat stays in. Result: ferrosilicon, tapped from the bottom of the furnace. Source: Furness, US 1,284,645 (1918). Not given: silicon content, iron proportion. Picture drawn by Youblob.