Reduction of Iron and Silver Ores. 225 



iron serves not only to decompose the chloride of silver as in the 

 Saxon method, but also to separate the sulphur from the sulphuret 

 of silver. When sulphuret of silver, alone; was mixed with iron filings, 

 it was, at the end of twenty four hours, so much reduced, that on 

 adding mercury, a large proportion of amalgam was obtained in a 

 few minutes. 



It is probable that the peroxide of iron in the pacos, in the colpa, 

 and that mingled in the magistral, act in a similar manner to the iron 

 filings. It results from these experiments, that iron perfects in a sen- 

 sible degree, the process of amalgamation, and in consequence, it has 

 been recommended that the amalgamation yards should be paved with 

 iron plates, and that the (tourte) amalgamation mass should be plough- 

 ed by iron ploughs, but the tourte is composed of schlichs forming so 

 heavy and stiff a paste as to render ploughing it almost impracticable. 



Lime seems to oppose itself to the combination of silver and mer- 

 cury, for an amalgam is very difficultly formed, by triturating mercury 

 and sulphuret of silver, and even after having formed a paste of the 

 ore, magistral, salt, and mercury, in which the globules of mercury 

 are no longer visible, if lime be added, the mercury soon shows itself, 

 coalescing into globules, wherever the lime is in contact with the mix- 

 ture. It is on this account, that the workmen say the lime cools the 

 tourte, because it prevents its working so rapidly. The lime, then, 

 has another use than that of removing the excess of sulphuric acid 

 in the tourte. 



The methods in use a few years since, in Mexico, were essentially 

 the same as has been mentioned, but it seems that by the proper mix- 

 ture of salt, magistral, and lime, the time requisite to perfect the opera- 

 tion is much lessened, as the proces now rarely requires more than 

 twenty days.* 



In Chili, the amalgamation is performed as in Mexico, except that 

 salt, and horse or mule dung are the only materials added to the ore 

 to assist in the amalgamation. In Chili, the heat of the sun, is, in 

 general, sufficient, with suitable attention, to perfect the amalgamation, 

 in eight or ten days in summer, or three weeks in winter ; but on 

 some of the high table lands of Peru, the amalgamation floor is built 

 upon arches, under which a fire is kept up to supply the necessary 

 temperature. 



The foreman judges of the perfection of the amalgamation by 

 washing a small portion of the amalgamation mass. If the remaining 



• Vide Jour. Eoyal Institution, No. 1, Oct., 1830, p. 142, et seq. 



