286 MINING INDTJSTEY. 



in some degree account for the low yield. Charge 12 ran five hours 

 with a somewhat higher result. It should be stated that the mercury of 

 charges 11 and 12 appeared to contain a small amount of lead, which 

 may have rendered it partially inactive. Charges 21, 22, and 23, of 

 the Kentuck table, were discharged at the end of four hours, without any 

 marked decrease in the production of bullion. It seems probable that in the 

 case of the latter the minerals are all easily reduced, and the amalgama- 

 tion is practically accomplished in the allotted space of time. In the case of 

 the Savage ore the base metals are but slightly attacked by the mercury, and 

 require more time for any chemical changes before amalgamation can take 

 place. There is considerable resemblance between Nos, 3 and 4 of the 

 Savage table, with a large excess of salt and sulphate of copper, and Nos. 

 6 and 7 with a solution of the sub-chloride of copper. The reason may be 

 found in the fact that in the former the chloride of copper formed would be 

 quickly reduced by the iron to the state of the sub-chloride, and similar condi- 

 tions produced as in the case of the latter. 



Chemistey op the Peocess. — The action and value of common salt 

 and sulphate of copper in the amalgamation of argentiferous ores, by what is 

 known as the patio process, has always been a somewhat disputed question. 

 Numerous theories have been advanced by metallurgists of long practical 

 experience in Mexico, to account for the reduction of the sulphide of silver 

 by the methods adopted in that country. The two which have obtained the 

 most prominence, and which chemists have received with most favor, differ 

 very widely in the manner the decomposition is supposed to be accomplished. 



The most plausible theory, and the one now generally adopted, is that of 

 Sonnenschmidt. He claims that the' salt and sulphate of copper react upon 

 each other, and produce sulphate of soda, which is neutral in its action, and 

 chloride of copper. This latter salt then acts upon the argentiferous sulphide, 

 and yields chloride of silver, sub-chloride of copper, and free sulphur. The 

 sub-chloride reduces a second portion of the sulphide of silver, and causes 

 the formation of an additional amount of the silver chloride, and sub-sulphide 

 of copper. The silver salt is then attacked by the mercury ; calomel, or sub- 

 chloride of mercury, is produced, while metallic silver is set free, which com- 

 bines with a second portion of the mercury, as amalgam. 



