Reduced Iron: Iron Oxide Heated in Hydrogen, USP 1860

Heat the precipitated iron oxide to a dull red in a stream of hydrogen and the oxygen leaves as steam, leaving metallic iron as a fine grey powder. This is the 1860 US Pharmacopoeia method, in a wrought-iron tube in a charcoal furnace. Hydrogen mixed with air explodes: the air must be driven out before the fire is lit. Source: United States Pharmacopoeia, 4th decennial revision (1860, publ. 1863), Ferrum Redactum. The metric figures and naming Kipp's apparatus are ours. The picture shows fine iron powder (Anonimski, CC0), not necessarily made this way.