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GOLD. 209

ninld. and eni1)raciiTi^- the s])ecial advantages claimed for
charcoal, may he ohtained at the dental depots. One of the
simplest forms of this kind is the asbestos melting and ingot
block shown in Fig. 175. Wdien in use, place a piece of
charcoal over the bowl-shaped portion of the ingot block,
as it facilitates heating the metal. The small asbestos slab
being placed in position to complete the mold, and retained
in place by clamping, the metal, when sufficiently fused, is
poured into the mold by tipping the block. The bowl or
crucible has a thin coating of whiting, to prevent borax or

Fig. 175-

other flux from adhering. Should this occur, however, rub
a little moist whiting in the bowl. The sides of the block
are encased in strips of wood, to protect the hands from
heat.
Carbon Molds.—A very ingenious, convenient, and useful
af)paratus, combining crucible and ingot-mold, by the use of
which ingots of gold, silver, etc., may be quickly obtained
without the use of a furnace, is shown in Fig. 176. The
crucible is of molded carbon, and is supported in position
by an iron side-plate. A clamp holds crucible and ingot-
mold in position, swiveling on a cast-iron stand.
The metal to be melted is placed in the crucible, and the
flame of the blowpipe directed on it until it is perfectly fused.
The waste heat serves to make the ingot-mold hot, and the
whole is tilted over by means of the upright handle at the
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