METALS AND CYANIDE PROCESSES 233 



with solution, not only is the coarse gold quickly romovod, ])ut 

 the rusty gold is made capable of amalgamation througli 

 being cleansed by the action of the cyanide and the electric 

 current, which are employed simultaneously, while the float 

 gold is either amalgamated directly or dissolved and then 

 precipitated. In these processes the precious metals are 

 recovered as amalgams, which need only retorting and melt- 

 ing to be ready for the mint. 



A novel method of overcoming the impermeability of 

 slimes is found in the suggestion of Count von Schwerin, 

 who proposes to remove water from wet clay and similar 

 amorphous fine slimes by passing through the mass an elec- 

 tric current, whereby the water is driven to the cathode and the 

 solid particles to the anode by electric endosmosis. The 

 apparatus consists of a wooden vat having for a bottom a 

 brass netting, which forms the cathode; the water being 

 drawn to the netting quickly nms off. 



In the MacArthur-Forrest process, the cyanide solution 

 containing the gold and silver is next run into zinc boxes for 

 the precipitation of the precious metals. The zinc boxes, 

 like the leaching vats, vary in character at the different works. 

 A form in common use in the United States is made of 2-inch 

 dressed plank, bolted together and painted with paraffin 

 paint; it is divided into six compartments, 13 by 20 inches 

 in cross section and 20 inches deep, and is provided with 

 a screen about 4 inches above the bottom, on which to place 

 the zinc shavings. About sixty pounds of shavings are re- 

 quired to fill the box. It is provided with an inlet and an 

 outlet pipe, and in the bottom of each compartment is 

 placed a 1-inch pipe closed with a stopcock, through which 

 the slimes are drawn off in cleaning up. The circulation in 

 the zinc box is secured by having the first partition of a com- 

 partment extend from the top of the box to within three 

 inches of the bottom, while the second partition extends 

 from the bottom of the box to within two inches of the top. 

 The screen for the zinc shavings is stretched between. The 

 solution from the entrance pipe falls to the bottom of the 

 box, passes under the first partition, rises up through the 

 zinc shavings, flows over the second partition, and thus pro- 



