Practieally the only ore which is regularly worked for IllereIlry is cinnabar. Mercury may be extracted from cinnabar in sev eral ways, but two methods only are used upon a large seal'. They are (11 extraction by heat ing the ore in the air, and (21 extraction by heating the ore iron, air being ex cluded. In both methods the chemieal reactions take place at temperatures alcove the boiling [milli of inereury. so that the latter is separated in the oaseons form and has to he condensed. Heating the cinnabar in the air is a process formed in shaft. reverberatory. or muffle nnee,, and is preferred to methods using lime r iron. inasnineh it is more economical and less datwerons to the workmen. whose health sh(mbl he eon-blercil. sine.' mercurial vapors are exceedingly injorbms. The leading objection to this method is the dilution of the mercurial vapors by sulphur dioxide, oxygen, and nitrogen, especially where shaft and reverberatory fur naces arc employed. by the products of minims tint). For these reasons it is rather difficult to condense the and therefore there are losses of the metal through incomplete eondensa• Lion. on the other hand, where the mercury is extracted by heating the cinnabar with lime or iron, are used in which the crushed ore is treated in small quantities. Concentrated curial are obtained from these retorts, and then condensed so that with a high grade of our the output is somewhat greater than by the first process. )hit as there is a much greater
expense of labor and fuel, and as the process is unhealthful for the workmen. on account of the mercurial vapors in emptying retorts; the process is less frequently eniph?yed.
The extraction of mercury in the air consists in heating cinnabar with an excess of air to a high temperature. The heating is usually plished in shaft or reverberatory furnaces, from which the gases Icass, into the condensers, eon. a series of tubes and chambers, and are there cooled tintil the mercurial gases condense into metallic mercury. while the other gases cape. The process requires great care to prevent the loss of mercury and danger to the workmen, and in the hest plants the loss of cury is at present not more than S per cent. of the nwtal in the ore, while every attempt is made to draw otr the mercurial gases by fans and other apparatus. and sit to keep them confined that they Will not be inhaled by the workmen. is transported in flasks closed by a screw stopper and holding about pounds of metal. Sheepskin bags are also used for this purpose. Consult of Metallurgy (New York, 1S98) ; Eggleston, Ilrtnlluray of Silrrr. Gold, and Mercury (New York. 1S90).