TO "PAN OUT" GOLD. 



53 



of mercury to 8 Ibs. of ore, and, if obtainable, a little cyanide 

 of potassium. Grind the whole for two or three hours until 

 the gold and mercury thoroughly amalgamate. Add water, 

 and when the amalgam has settled at the bottom of the 

 vessel pour the lighter matter off, collect the amalgam and 

 squeeze it through chamois leather. The residue must be 

 heated to drive off any 

 mercury remaining, or if 

 the amalgam be treated 

 with nitric acid, the mer- 

 cury will be dissolved 

 and the gold left. 



An addition of a little 

 sodium will assist the 

 amalgamation and prevent 

 loss due to " flouring." 



Sometimes as much as 

 30 percent, of what ought 

 to be the proper yield is 

 lost in the tailings in a 

 free milling ore. 



On alluvial diggings, the operation of washing the gold 

 dirt is usually conducted by means of sluices, having an 

 inclination of a very slight gradient. These sluices consist 

 of a series of troughs formed by planks nailed together, the 

 length of each being about 10 or 12 feet, the height 8 inches 

 to 2 feet, the width 1 to 4 feet. By making one end of the 

 bottom plank of each trough 4 inches narrower than at the 

 other, the troughs can be telescoped into one another, and 

 so a sluice of very great length can be formed. Across the 

 inside of the bottom planks small narrow strips of wood, 

 2 inches or so thick, and 3 or more inches wide, are fixed 

 across, or sometimes at angles of 45 to the side of the 

 trough, at short intervals apart. Eunning water washes 

 downwards the earth thrown into the sluice, which is open 

 on the top side, and the gold dust accumulates (sometimes 

 assisted by the aid of mercury allowed to trickle out of a 

 vessel from riffle to riffle) in front of the bars, while the 

 lighter matter is washed downwards. 



FIG. 36. 



