Bulletin . ext, a bother-some accumulation of dust was at first obtained in the condensers. Tocorrect this and keep the dust from passing into the condensers, a Cot-trell fume precipitator, called the hot treater was installed betweenthe furnace and the first condenser. (See Photo No. 35, ante.) To 252 CALIFORNIA STATE MINING BUREAU. prevent the mercury from condensing in this treater, the temperatureof the gases (as already mentioned) is kept above 600° F. on leavingthe furnace. As a precaution to recover any quicksilver which mighthave condensed in case of irregularities occurring in the fur
Bulletin . ext, a bother-some accumulation of dust was at first obtained in the condensers. Tocorrect this and keep the dust from passing into the condensers, a Cot-trell fume precipitator, called the hot treater was installed betweenthe furnace and the first condenser. (See Photo No. 35, ante.) To 252 CALIFORNIA STATE MINING BUREAU. prevent the mercury from condensing in this treater, the temperatureof the gases (as already mentioned) is kept above 600° F. on leavingthe furnace. As a precaution to recover any quicksilver which mighthave condensed in case of irregularities occurring in the furnace oper-ation, the hot-treater dust is run into a settling tank before being dis-charged to the dump. Following the last condensing chamber Is a sec-ond Cottrell precipitator (Photo No. 55), called the cold treater, tothrow down any remaining mercury mist in the fumes. The fuel consumption of this furnace is stated to have proven ratherhigh, being approximately 8 gallons of oil per ton of ore treated, as. Photo No. 54. Top, or Drying-hearth, of Herreschoff Furnace. Feed hopper is seen in upper part. against 5-6 gallons per ton for a 50-tou Scott furnace. The installa-tion cost of the multiple-hearth type of furnace is much less than theScott, being stated to be about $20,000 for a 100-ton plant, or $200 perton-day capacity (1916; but for 1917 nearly double that). Thecheapest operation of this type of urnace is obtained with the largerunits or with several units under a single roof, as a single machinistcan attend to the mechanical features of several units. To repair therabble arms or other parts of the interior mechanism, the furnace mustbe shut down and cooled off. This is apt to occur oftener than interiorrepairs are required in a Scott furnace, though Herreschoff units have QUICKSILVER RESOURCES. 253 been in opei-ation on copper ores for more than two years without suchrepairs. Another furnace of the multiple-hearth type which mightprove adaptable for the treatment of qu
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