[Figs. 689], [690], [691.] represent the reverberatory furnace generally employed in the Hartz, in the district of Mansfeldt, Saxony, Hungary, &c., for the treatment of black copper, and for refining rose copper upon the great scale. An analogous furnace is used at Andreasberg for the liquefaction or purification of the mattes, and for workable lead when it is much loaded with arsenic.
[Fig. 689.] presents the elevation of the furnace parallel to the line I K, of the plan [fig. 690.]; which plan is taken at the level of the tuyère n, of [fig. 691.]; [fig. 691.] is a vertical section in the line L M, [fig. 690.] k represents one of two basins of reception, brasqued with clay and charcoal; n, n, two tuyères, through which enters the blast of two pairs of bellows, like those shown at [Cupellation of Silver]; q, door by which the matter to be melted is laid upon the sole of the furnace; v, v, two points where the sole is perforated, when necessary to run off the melted matter into either of the basins h; x, door through which the slags or cinders floating upon the surface of the melted metal are raked out; y, door of the fire-place. The fuel is laid upon a grate above an ash-pit, and below the arch of a reverberatory which is contiguous to the dome or cap of the furnace properly so called. In the section, [fig. 691.], the following parts may be noted: 1, 2, 3, mason-work of the foundation; 4, vapour channels or conduits, for the escape of the humidity; 5, bed of clay; 6, brasque composed of clay and charcoal, which forms the concavity of the hearth.
[Figs. 692], [693], [694.], show the furnace employed for liquation in one of the principal smelting works of the Hartz. [Fig. 694.] exhibits the working area charged with the liquation cakes and charcoal, supported by sheets of wrought iron; being an image of the process in action. [Fig. 693.] is the plan, in the line F, G, of [fig. 692.]
A liquation cake is composed of—
Black copper holding at least 5 or 6 loths (21⁄2 or 3 oz.) of silver per cwt., and weighing 90 to 96 lbs.