as to effect the maximum degree of fusion with a minimum of oxidation. When the operation is conducted during winter, the product is less abundant, and of inferior quality. After the charge is exhausted, a new one can not be introduced till the mass has cooled down, occupying a period of ten days to a month, according to the size of the calcarone. The discharging has to be done slowly and cautiously, on account of the sulphurous fumes liberated. The consumption of sulphur (as fuel) in the heating is about fifty per cent of the total amount contained in the ore. Thus, to obtain one ton of sulphur, there is consumed as fuel about another ton, worth say five pounds, and performing a duty which could be much more satisfactorily accomplished by two hundred-weight of coal, costing perhaps five shillings.
A great improvement in the Sicilian calcarone has been introduced by P. Le Neve Foster, and worked with good results, showing an increase of yield of thirty per cent above the ordinary plan. According to his description, the waste heat from an ordinary calcarone, after all the sulphur has been run off, is utilized to heat to the required temperature the charge of ore placed in his kiln, and, as soon as the moisture has been driven off and the heat is great enough, the charge is fired from the top. The combustion, fed with hot air containing some sulphurous-acid gas, is very slow, hence the loss of sulphur by burning is less than when, as in the ordinary calcarone, the ore has to be heated entirely by the combustion of the sulphur. The apparatus (shown in Fig. 3, prepared from a drawing kindly furnished me by the inventor) consists essentially of three parts: 1. The flue, or conductor of heat; 2. The kiln, in which the ore is treated; 3. The chamber for the condensation of the sulphur that is volatilized during the fusion, and in which it is collected.
The kiln may be of any suitable form to contain two charges of ore, but a rectangular chamber is found to be most convenient, with floor sloping toward the front. The chamber consists of four walls, preferably not covered with an arch, as affording greater facility for charging and discharging. The kiln communicates, by means of a flue, A, with the back of an ordinary calcarone, B, which furnishes the heat necessary for melting the sulphur from the one contained in the kiln, C. The upper portion of the calcarone should be covered with a layer of genese (spent ore), so as to prevent the dispersion of heat by any other channel than that offered by the flue. A, which is provided with a damper, D, so as to regulate the admission of heated air by openings, E, at the upper back part of the kiln. A rectangular opening, F, is left in the front wall of the kiln, from which the melted sulphur is run. This opening, if of sufficient size, may serve for discharging the spent ore at the termination of the fusion. From the upper part of the opening, and also in the front wall, slightly above the level of the floor, flues, G, communicate with a horizontal passage, II, which is made large enough to serve as a condensation chamber, on the walls of which
