•V3 The Patio and Cazo Process. 



addition of mercury is made. This will generally be introduced in 

 several portions; one quarter only being added at first. In ten or 

 fifteen minutes an assay is taken, with an open horn attached to a 

 long handle, so as to pick out the heavy parts of the ore and amal- 

 gam. This is washed, and if the amalgam shows itself as a 

 clear gray sand, polvo, the charge is ready for the second addi- 

 tion of mercury. The same quantity as before is added, the 

 heat and movement being kept up. In an hour or two after 

 the start, another assay is taken, and another addition of mercu- 

 ry made, and so on until an amalgam containing two parts of 

 mercury for one of silver results. The operation is then con- 

 sidered as finished. The amalgamator, cazeador, takes a last 

 assay, prueva en crndo, which he washes to get out the gan- 

 gues, then adds a large excess of mercury to dissolve out the 

 amalgam, separates it from the tails, and then examines it by 

 rubbing it against the sides of the vessel to see if any of the 

 ores remain, If they do, the operation must continue ; if not. 

 and the amalgam remains fluid, it is stopped. At the end of six 

 hours the operation is complete. The muddy material is run oft' 

 into outside receptacles, and what remains in the cazo is dipped 

 out, and treated in oateas with an amount of mercury equal to 

 that which has already been used. 



It is of the greatest importance, during the whole of the 

 operation, to prevent anything from adhering to the bottom. 

 If the salt was introduced before ebullition took place, it 

 would collect on the bottom, and the apparatus would have to 

 be emptied before it could be removed. It is more especially 

 important to prevent any adherence of mercury, which would 

 prevent the- action of the salts of silver on the copper, and 

 thus make the amalgamation progress very slowly. It would 

 besides cause a great loss in mercury, as it alone, and not the 

 copper, would reduce the silver salts. If the proportion of the 

 mercury and silver are as two to one, no adherence of the 

 mercury takes place. 



The cazo was replaced by a much larger vessel,* 2.15 m. diame- 

 ter above, and 1.80 m. below, and 0.85 m. deep, called a fondon. 



* Ann. des Mines, 6s., Vol. 20, p. 216, PI. Ill, Fig. 7. 



