In order to keep the plates in proper condition so that successful amalgamation may be maintained, they must be prepared carefully, and the closest watch kept over them. The setting of the plates has already been described on p. 121. The silver-plated copper table is preferred in California from the ease with which it is kept clean, but is not used in the Transvaal. It is not considered desirable to put on it as much mercury as it will hold, since, if the amalgam is too fluid, losses are sustained by scouring, but, on the other hand, if the amalgam becomes too hard and dry from absorption of gold and silver, further amalgamation is checked and fresh mercury must be added.
The condition of the inside plates is regulated by the amount of mercury supplied to the mortar. In Colorado there is an opening at the front of the battery and above the screen frame, ordinarily covered by canvas, which can be lifted up by the millman, who introduces his arm, and determines by passing his hand over the front plate, whether the right amount of mercury is being added by the feeder. The regulation of the addition of mercury is ….Read more