Page:Popular Science Monthly Volume 26.djvu/508

492 distilled sulphur, placed outside the furnace. The apparatus is generally employed on rich material, or on that obtained from the calcaroni; but it is also applicable to ores which are too poor to burn in the calcaroni, though the profit in that case must be small. The heat generated in the doppione is likely to encourage chemical action between the sulphur and any lime carbonate that may chance to be present in the mineral, creating a further loss of sulphur. The pots are charged and discharged by opening the lids, which are kept luted during the distillation. The volatilized sulphur is conducted by the cast iron tub, b, into the receptacle, c, over which a small current of cold water constantly flows, reducing the sulphur to a fluid condition; it then escapes into the dish, d, beneath, whence it can be ladled into the molds. The pots last for about three hundred working-days, and the furnace serves about the same time with a couple of repairings. The workman is expected to turn out one hundred pounds of clean sulphur from every one hundred and nine pounds of calcarone sulphur.

The principle underlying the use of calcium chloride is that, while raising the boiling-point of water to about 239° Fahr. (115° C), the melting-point of sulphur, it is cheap and inert in the presence of sulphur. The water to be used in the melting process is charged with sixty-six per cent of the calcium chloride, and heated to boiling, in which state it is run into the vessel containing the sulphur to be melted. No doubt the sulphur is efficiently melted, but the very slight difference in specific gravity between the sulphur and the associated impurities, from which it had been melted out, practically precludes any real separation taking place. Consequently, the process is virtually a failure, as I am assured by those who have worked it.

At the Rabbit Hole mines, Humboldt County, Nevada, advantage is taken of the liquidity of sulphur at 232° Fahr. (111° C), to use steam at sixty to seventy pounds pressure for melting the sulphur out of the gangue. The apparatus employed consists of a cylindrical iron vessel, about ten and a half feet high, divided into an upper and a lower compartment, by means of a horizontal sheet-iron diaphragm perforated with one-fourth-inch holes. As soon as the upper compartment is charged with ore (about two tons), steam is introduced for about half an hour, and the sulphur, liquefied by the heat, flows down through the diaphragm into the lower compartment, kept at the proper heat by injection of steam, and escapes by an outlet, opened at intervals into a receptacle placed outside. When water commences to flow out with the sulphur, steam is injected at full pressure for a few minutes, to clear out as much as will come, and the solid residue is afterward removed through a door above the diaphragm. Each charge requires about three hours for its treatment. The process is adapted to ores which, for poverty and other reasons, can not be economically worked by calcaroni, or other recognized methods.

While hot water and steam have no solvent action upon sulphur,