PRECIOUS METALS 109 



ing the amalgam from the plates too thoroughly, for the amalgama- 

 tion is not complete when the plates are new or perfectly free from 

 the amalgam, that is, "experienced" plates are far more efficient 

 in t he extraction of the gold and silver than the "inexperienced." 

 (12) By using too slow a current of water. If the current be too 

 slow, the plates become covered with slime, and this prevents the 

 gold and the silver from coming directly in contact with the 

 amalgam. (13) By using too rapid a current of water. This pre- 

 vents the metal from being caught on the amalgamating plates, 

 that is, the heavy current of water simply carries it away. (14) 

 By not keeping the mercury clean. This prevents the amalgama- 

 tion from taking place. Whenever mercury is covered with oil from 

 the machinery, or oily exudations from the hands, it must be redis- 

 tilled or treated with lye to cut the oil. (15) By the flouring 

 of the mercury, that is, the reduction of the mercury to so fine a 

 state of subdivision that it will not adhere to the amalgamating 

 pans. (16) By too few amalgamating machines, as where the 

 ore is rich and the quantity required to pass over the plates is 

 too great for one machine to do the work. (17) By too short 

 sluices or plates; by using the blankets too long; and by leaving 

 the plates in front of the stamps so long that they become 

 charged with mud and other debris and prevent the uniform 

 feeding of the gold upon the amalgamating plates. 



