288 MmiNG ENDUSTEY. 



clearly to indicate that the benefits derived from their use are partly to aid 

 in converting the sulphide into chloride of silver, as in the patio, and 

 partly to decompose such minerals as are but slightly attacked by the mer- 

 cury. In the "Washoe process, however, the large quantity of iron present 

 must tend greatly to produce sub-chloride of copper almost as soon as the 

 chemical agents are throw^n into the pulp. 



Notv^'ithstanding the importance of common salt and sulphate of copper 

 in the patio, and, under certain conditions in the pan, their value must be 

 considered as only secondary in the decomposition of a large proportion of 

 the Comstock ores. The advantages derived from their use are show^n to 

 be exerted chiefly upon such minerals as blende and galena, which are but 

 slightly attacked by the mercury. But the amounts employed are in most 

 cases too small to effect any very favorable results. On the other hand, if a 

 sufficiently large proportion of the reagents are consumed in the pulp, in 

 order to produce the beneficial returns, it is always at the expense of pre- 

 serving the necessary purity of the mercury. 



The quantity of salt deemed necessary by mill-men varies from one 

 quarter of a pound up to seven or eight pounds per ton ; scarcely any two 

 establishments have the same rule. Its action upon the ore, without sulphate 

 of copper, in producing any marked results may well be doubted. 



The consumption of the sulphate of copper also depends upon the ideas 

 of the amalgamators, but the amounts do not differ so widely as in the case 

 of the chloride of sodium. It ranges from one quarter of a pound to three 

 pounds per ton. 



The addition of the sulphate, without salt, is of la^e years a common prac- 

 tice. The opinion among those who work their ore in this way is that it gives 

 a little better yield than when mercury alone is employed, particularly where 

 the ore indicates the presence of galena in any considerable amount, in which 

 case it is said to quicken the mercury and render it more energetic. 



Continued experience appears to determine this fact with a considerable 

 degree of certainty. In working ores containing only a small percentage of 

 lead the quicksilver very soon becomes dull and inactive, or, as it is techni- 

 cally termed, it sickens, and the yield from the pan is consequently low. Lead 

 is one of the most deleterious metals in destroying the amalgamating energy 



