292 Transactions of the 



emulsion of the rock in the barrel or pan. A vast proportion of the 

 mercury yearly produced is employed in amalgamation; most of the re- 

 mainder is consumed in the manufacture of vermilion paint and mercu- 

 rial drugs. 



Quicksilver sometimes occurs native in connection with its ores; but 

 generally in inconsiderable quantities. It is also sometimes an ingre- 

 dient of a complicated mineral called tetrahedrite, but by far the most 

 important ore of mercury is the sulphide called cinnabar, and identical 

 in composition with the vermilion of commerce. The largest deposit of 

 this ore is at Almadus, in Spain. The Almaden mine has been worked 

 since seven hifndred B. C, and is scarcely even well developed yet. The 

 second largest deposit is at New Almaden, in this State; but, as thus far 

 known, it does not approach the Spanish deposit in value. 



Quicksilver belongs to the same general group of metals as gold and 

 silver, and like them, its affinities are weak — its components are readily 

 decomposed. The beneficiation of cinnabar depends on the fact that 

 sulphur unites with much more strength with most other substances 

 than it does with mercury. If cinnabar be heated with lime, the sul- 

 phur of the ore combines with it, forming sulphide and sulphate of lime, 

 and having metallic mercury. If we heat cinnabar in a current of air, 

 the mineral is also decomposed; the sulphur unites with the oxygen of 

 the air to sulphurous acid, the unpleasant smelling gas we have met so 

 often in these lectures, and metallic mercury is again left behind. If we 

 form an illustrative diagram of these changes we get: 



Mercuric sulphide — Quicksilver. 



Mercury — Sulphide of lime, and gypsum. 



Mercuric sulphide — Oxygen. 



Mercury — Sulphurous acid. 



Perhaps } 7 ou may remember that when sulphur of lead, or galena, is 

 heated in a current of air, the oxygen attacks both constituents of the 

 mineral, and we get, as here, sulphurous acid, but in place of metallic 

 quicksilver oxide of lead results. Gold, silver, platinum, and mercury, 

 the noble metals, are not attacked to any extent by free oxygen, and 

 hence, in the present case, metallic mercuiy is produced by simple 

 roasting. 



QUICKSILVER POSSESSES A PROPERTY 



TVhich greatly simplifies the operations subsequent to its isolation in a 

 metallic form. It is highly volatile, and boils at a temperature of six 

 hundred and seventy-five degrees. It, therefore, distils off from the ore 

 during the roasting, and only requires to be conducted through proper 

 condensing apparatus to be liquified, and obtained in a marketable shape. 

 If gold and silver were only volatile at furnace temperatures, we could 

 beneticiate their ores in the same way — i. e., sufficiently volatile; for, 

 though we cannot distil these metals in any ordinary furnace, very 

 small amounts of gold and silver do pass off as vapor, when they are 

 melted, and their volatility is, consequently, great enough to necessitate 

 troublesome precautions, and to occasion loss, though it is insufficient 

 to be turned to practical account. 



Retorting quicksilver ores with lime is a method of beneficiating 

 them, now seldom practiced, except for assay. "When used, this method 

 differs but little from the retorting of amalgam, which I described in my 

 last lecture. The retort is filled with a mixture of cinnabar and lime, 

 and heated. The mercurial vapor passes out of the retort through 

 tubes, cooled with water, and the liquid quicksilver drops from the end 



