The Patio and Cazo Process. : >1 



The proportion of the silver dissolved in the salt was 4.7 per 

 cent. 



If mercury, sulphide of silver, chloride of sodium, sand and 

 water are worked together, seven-eighths of the silver present is 

 extracted, three times as much as when the salt was not theie. 

 If oxide of iron is present in the mixture, chloride of iron will 

 be formed, which is reduced to sub-chloride by the mercury, and 

 a chloride of mercury is formed. A very small amount of oxide 

 of iron produces a very considerable loss, as the sub-chloride 

 constantly changes to chloride of iron, in contact with the air. If 

 to this last mixture sulphate of copper is added, a little less silver 

 is obtained, and the loss of mercury is large. If proustite, which 

 contains 65.5 per cent, of silver, 15.1 of arsenic, and 19.4 of sul- 

 phur, is substituted for the sulphide of silver, twice as much silver 

 combines with the mercury when chloride of copper is present. 

 It requires a great deal of shaking to decompose the sulphide of 

 silver. When sulphide of zinc is present with chloride of copper, it 

 causes the formation of sulphide of copper and chloride of zinCj 

 so that ores which contain blende always amalgamate badly. 



From these reactions it would seem that, during the first two or 

 three days, chlorides of copper and iron are produced by the 

 action of the magistral on the salt ; that chloride of silver is 

 formed by the action of these chlorides on the easily attacked 

 ores, and even on the sulphide of silver; that the chloride of silver 

 is dissolved probably at once in the excess of salt. In chloridizing 

 the silver, the copper and iron salts have become reduced to sub- 

 chlorides, which in the presence of sulphide of silver form the 

 chlorides, and produce metallic silver, or, when it is absent, 

 quickly become oxy-chloride, and produce no further action. 

 !Sub chloride of copper reduces sulphide of silver; but the sub- 

 chloride of iron does not. The presence of mercury prevents the 

 formation of an excess of chloride of copper, for as soon as there 

 is an accumulation of it, it acts on the mercury and is reduced to 

 sub-chloride. Just as soon as the mercury is introduced the free 

 silver is amalgamated; the chloride of copper which is still in the 

 pulp forms calomel and sub-chloride of copper, which acts on the 

 sulphide of silver and leaves it as metal, to be acted on by the 

 quicksilver. 



Some authors, especially Mr. Bowering, deny that chloride of 



