Excerpt from A Textbook on Metallurgy of Gold, Silver, Copper, Lead, and Zinc: Surface Arrangements at Reduction Works, Ore Dressing and Milling, Sampling Ores, Roasting and Calcining Ores, the Cyanide Process When the mercury becomes sickened it refuses to act upon the gold, and hence the gold is not recovered by this process. If, therefore, it is possible to keep the mercury bright and active, as may be done by adding chemicals, a larger percentage of precious metals can be recovered. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.