Cyanide Leaching Tank (Gold Extraction)
In the gold extraction process, finely crushed ores are leached in vats with a very diluted solution of Potassuim Cyanide (KCN), containing 0.05 to 0.3 percent KCN (or its equivalent, Sodium Cyanide, NaCN) which is allowed to remain for twelve to twenty-four hours to dissolve the gold.
John H. Finley ed. Nelson's Perpetual Loose-Leaf Encyclopaedia (vol. 5) (New York, NY: Thomas Nelson and Sons, 1917) 479