English: Detailled drawing of a Huntington-Heberlein roasting pot, used to roast galena.

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Treatment of Galena. — By the Huntington-Heberlein process, called also the " H and H process," the galena-bearing ore is given an incomplete, rather rapid roast, to reduce the amount of sulphur to 12 to 14 per cent. The product from the roaster is mixed with a certain proportion of limestone and silicious ore, wet down, and charged into a hemispherical cast iron pot 8i ft. diameter by 4 ft. deep, having a capacity of 8 to 10 tons as shown in Fig. 82. Within the pot, and forming a false-bottom, is placed a circular arched plate perforated with |-in. holes to admit air to the charge under pressure. Upon the false-bottom is scattered a wheelbarrow-load of ashes, then a carload (one ton) of hot ore from the roaster. On this is dumped 8 tons of charge wet to about 6 per cent moisture. Air, under the pressure of a few ounces, is admitted beneath the false-bottom, and coming up through the hot ore, it produces a burning-temperature and starts the combustion of the charge. The heat gradually ascending to the top, the charge becomes red-hot, and SO2 and SO3 escape. At the end of the roasting, which lasts sometimes sixteen hours, there remains only 3 to 5 per cent sulphur if the charge is properly burned. The pot is now inverted to discharge the contents, and this falls out in an agglomerated, red-hot mass. It is broken to a size suited to subsequent treatment in the blast-furnace.