60 The Patio and Cazo Process. 



being turned for a short time, and the tails, amalgam and mer- 

 cury discharged as in the Freiberg process. The amalgam re- 

 covered is not pure. It contains oxide of copper, produced by 

 the action of the lime of the gangue on the chloride of copper, 

 and the sulphides of copper produced by the action of the 

 sulphate of copper on the sulphide of silver. These must be 

 separated, the one by mechanical means, the other by chemi- 

 cal action. The first is done in a Una. The amalgam is 

 charged with ten per cent, of fresh mercury. Water is added, 

 and the muller is made to revolve at the rate of sixteen 

 turns a minute. When the water which comes off is entirely 

 clear, all the sulphide and a part of the oxide of copper will 

 have been removed. To remove the oxide, all the water of the 

 Una is run off, and two per cent, of carbonate of ammonia is ad- 

 ded. The muller is revolved for five hours. At the end of that 

 time it is stopped, and the amalgam washed with water. If this 

 has been properly done no oxide will be left. The amalgam is 

 distilled in a capellina. The mercury which is strained from 

 the amalgam becomes little by little quite impure. After it has 

 been used five or six times, it amalgamates very slowly. It is 

 then purified by adding to it 20 grams of sodium amalgam for 

 every 100 kilos, of impure mercury. 



The resulting silver, pina, is refined in a reverberatory fur- 

 nace. It contains some arsenic, which is extracted by the iron 

 of the tools, and floats on the surface of the bath and is removed. 

 The method of refining does not differ in other respects from 

 that used elsewhere. The silver obtained is 980 fine. By this 

 process, tails which do not contain more than $6 to $8 to the ton, 

 and ores of from $10 upward, are worked. When the ores do not 

 contain more than $80 to the ton, the tails do not contain much 

 more than two to three dollars. Plenty of good water is a ne- 

 cessity for such works, both for purposes of washing and for 

 power if possible. 



To treat eight tons of ore in twenty-four hours, requires an. 

 area of 500 square meters for the ores, and one of 1,000 

 square meters for drying the pulp; two Chilian mills requir- 

 ing about six horse-power; two settling tanks, and two amalga- 

 mation barrels requiring about eight horse power; a vat to col- 

 lect the water from washing the barrels, to recover the floured 

 mercury; one trough for washing the amalgam; one distilling 



