Cyaniding replaced chlorination because it was a simpler, cheaper process, and did not require prior roasting of sands. This diagram contains a very simplified version of the process - cyanide is mixed with water, and percolated through vats filled with battery sand. This dissolves the gold, which is precipitated by passing the solution over charcoal or zinc shavings contained in a box (bottom of diagram). The process continues until no more gold is precipitated.