224' On the Principles Involved in the 



1. In consequence of the minute state of division in the immense 

 mass of schlich, by the washing process, many of the particles of 

 mercury may be carried off, in a state of suspension in the mud. 

 Even in the Saxon amalgamation works, where the process is con- 

 ducted with the greatest skill and care, a sensible portion of mercury 

 is carried off in this way. 



2. The contact of the mercury with the various metallic and other 

 materials, moistened with saline solutions, forms an infinity of galvanic 

 arrangements, whose actions are slow indeed, but prolonged, and fa- 

 vor the oxidation of the mercury, and various other chemical affinities. 



3. The heat of the mass, produced by the various chemical 

 changes, and increased by a tropical sun, might be sufficient to par- 

 tially oxidize the mercury, when in contact with the air. 



The mines of Almaden, in Spain, and of Idria, in Carniolia, have, 

 in general, furnished the mercury consumed in the Mexican mines. 

 The mine of Huan-cavelica, in Peru, has occasionally furnished some 

 mercury. The Mexican mines consumed previous to 1804, an an- 

 nual average of sixteen thousand quintals of mercury. 



6. Chemical changes in the Mexican method. 



M. Humboldt is of opinion, that the sulphates of iron and copper, in 

 the magistral, decompose the "muriate of soda," (chloride of sodium,) 

 forming sulphate of soda and " muriate of silver," (chloride of silver,) 

 and that the latter is, in part, decomposed by the oxide of iron set 

 free, and the other by the mercury. Two affinities are here brought 

 into action, viz. the affinity of iron, copper, fee. for chlorine, and the 

 affinity of mercury for silver, both tending to the decomposition of 

 the chloride of silver. He is also of opinion, that the reason of the 

 usefulness of lime or ashes, when added, under certain circumstances, 

 during the amalgamation, is, that they serve to prevent the excess of 

 sulphuric acid, formed by the decomposition of pyrites, from acting 

 on the mercury. 



M. Humboldt and Gay Lussac, in mingling cold, the natural sul- 

 phuret of silver, sulphate of iron, muriate of soda, and lime, have 

 not been able to obtain muriate of silver at ordinary temperatures, 

 at the end of a fortnight, but when heated from 86° to 96° F., 

 tliey obtained it at the end of a few hours. They also observed, 

 that an amalgam was formed, when the materials were mixed cold, 

 • but that it was formed much more abundantly, when iron filings 

 were mingled with the other materials, and they conceive that the 



