Carbon as Pure Graphite: Coke and Sand Heated round a Coke Core in an Electric Furnace (Acheson, US 568,323)

Acheson found that carbon heated on its own hardly turns to graphite, but carbon first bound to silicon does. Coke and sand packed round a coke core form silicon carbide when the current heats the core; hotter still, the silicon boils away and the carbon is left as pure graphite, which grows outward as the core. Result: pure carbon in its graphite form, sorted like native graphite. Source: E. G. Acheson, US patent 568,323 (1896), pp. 1-3 and drawing (shown above). The furnace runs at hundreds of volts and up to 1000 amperes.