Another authority says in respect to the Liberty Bell mill: "The recovery by amalgamation is materially smaller than in previous years of water-amalgamation; the process is more expensive both in labor and material, and requires more skill; and the consumption of cyanide is considerable .... The plates are kept rather wet and any drip is caught in a trap."

The following quotation is from another authority : "The solvent action on amalgamating plates greatly depends upon the amount of amalgamable gold in the ore. If the ore contains much gold and the plates are not cleaned too closely, they will last indefinitely, being protected by a coating of amalgam. If the ore be low-grade, it is next to impossible to keep the plates in good " catching" condition; they are rapidly eaten up by the solution .... I find no advantage whatever in using silver-plated copper when crushing in cyanide. This is contrary to water practice. The plain copper after the first careful dressing catches and builds amalgam splendidly, and does not harden so much as silvered plates."

At the Alaska Treadwell1 concentrate plant: "When grinding in cyanide solution stronger than 1 Ib. per ton, followed by amalgamation, it was difficult to keep the plates bright, due to a dull white surface deposit, which if allowed to remain turned to a dull gray. A muntz metal plate was substituted for the copper plate, but as all the plates were silver-coated no variation in the result was noted."

John Gross says: "It sometimes becomes advisable to attempt the saving of a portion of the precious metals in ores that are too coarse for the ordinary system of cyanidation, owing to the high strength of cyanide solution carried, or an excess of lime in the solution. I have seen plates almost entirely eaten through in the course of several months, using a battery solution containing 2 Ib. of KCN and carrying a protective alkalinity of about 1 Ib. of lime."